1
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Zald DH. The influence of dopamine autoreceptors on temperament and addiction risk. Neurosci Biobehav Rev 2023; 155:105456. [PMID: 37926241 DOI: 10.1016/j.neubiorev.2023.105456] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 10/22/2023] [Accepted: 10/31/2023] [Indexed: 11/07/2023]
Abstract
As a major regulator of dopamine (DA), DA autoreceptors (DAARs) exert substantial influence over DA-mediated behaviors. This paper reviews the physiological and behavioral impact of DAARs. Individual differences in DAAR functioning influences temperamental traits such as novelty responsivity and impulsivity, both of which are associated with vulnerability to addictive behavior in animal models and a broad array of externalizing behaviors in humans. DAARs additionally impact the response to psychostimulants and other drugs of abuse. Human PET studies of D2-like receptors in the midbrain provide evidence for parallels to the animal literature. These data lead to the proposal that weak DAAR regulation is a risk factor for addiction and externalizing problems. The review highlights the potential to build translational models of the functional role of DAARs in behavior. It also draws attention to key limitations in the current literature that would need to be addressed to further advance a weak DAAR regulation model of addiction and externalizing risk.
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Affiliation(s)
- David H Zald
- Center for Advanced Human Brain Imaging and Department of Psychiatry, Rutgers University, Piscataway, NJ, USA.
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2
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Hettiarachchi P, Johnson MA. Characterization of D3 Autoreceptor Function in Whole Zebrafish Brain with Fast-Scan Cyclic Voltammetry. ACS Chem Neurosci 2022; 13:2863-2873. [PMID: 36099546 PMCID: PMC10105970 DOI: 10.1021/acschemneuro.2c00280] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Zebrafish (Danio rerio) are ideal model organisms for investigating nervous system function, both in health and disease. Nevertheless, functional characteristics of dopamine (DA) release and uptake regulation are still not well-understood in zebrafish. In this study, we assessed D3 autoreceptor function in the telencephalon of whole zebrafish brains ex vivo by measuring the electrically stimulated DA release ([DA]max) and uptake at carbon fiber microelectrodes with fast-scan cyclic voltammetry. Treatment with pramipexole and 7-OH-DPAT, selective D3 autoreceptor agonists, sharply decreased [DA]max. Conversely, SB277011A, a selective D3 antagonist, nearly doubled [DA]max and decreased k, the first-order rate constant for the DA uptake, to about 20% of its original value. Treatment with desipramine, a selective norepinephrine transporter blocker, failed to increase current, suggesting that our electrochemical signal arises solely from the release of DA. Furthermore, blockage of DA uptake with nomifensine-reversed 7-OH-DPAT induced decreases in [DA]max. Collectively, our data show that, as in mammals, D3 autoreceptors regulate DA release, likely by inhibiting uptake. The results of this study are useful in the further development of zebrafish as a model organism for DA-related neurological disorders such as Parkinson's disease, schizophrenia, and drug addiction.
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Affiliation(s)
- Piyanka Hettiarachchi
- Department of Chemistry and R.N. Adams Institute for Bioanalytical Chemistry, University of Kansas, Lawrence, Kansas 66045
| | - Michael A Johnson
- Department of Chemistry and R.N. Adams Institute for Bioanalytical Chemistry, University of Kansas, Lawrence, Kansas 66045
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3
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Lycas MD, Ejdrup AL, Sørensen AT, Haahr NO, Jørgensen SH, Guthrie DA, Støier JF, Werner C, Newman AH, Sauer M, Herborg F, Gether U. Nanoscopic dopamine transporter distribution and conformation are inversely regulated by excitatory drive and D2 autoreceptor activity. Cell Rep 2022; 40:111431. [PMID: 36170827 PMCID: PMC9617621 DOI: 10.1016/j.celrep.2022.111431] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Revised: 07/22/2022] [Accepted: 09/08/2022] [Indexed: 11/30/2022] Open
Abstract
The nanoscopic organization and regulation of individual molecular components in presynaptic varicosities of neurons releasing modulatory volume neurotransmitters like dopamine (DA) remain largely elusive. Here we show, by application of several super-resolution microscopy techniques to cultured neurons and mouse striatal slices, that the DA transporter (DAT), a key protein in varicosities of dopaminergic neurons, exists in the membrane in dynamic equilibrium between an inward-facing nanodomain-localized and outward-facing unclustered configuration. The balance between these configurations is inversely regulated by excitatory drive and DA D2 autoreceptor activation in a manner dependent on Ca2+ influx via N-type voltage-gated Ca2+ channels. The DAT nanodomains contain tens of transporters molecules and overlap with nanodomains of PIP2 (phosphatidylinositol-4,5-bisphosphate) but show little overlap with D2 autoreceptor, syntaxin-1, and clathrin nanodomains. The data reveal a mechanism for rapid alterations of nanoscopic DAT distribution and show a striking link of this to the conformational state of the transporter.
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Affiliation(s)
- Matthew D Lycas
- Molecular Neuropharmacology and Genetics Laboratory, Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Maersk Tower 7.5, 2200 Copenhagen, Denmark
| | - Aske L Ejdrup
- Molecular Neuropharmacology and Genetics Laboratory, Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Maersk Tower 7.5, 2200 Copenhagen, Denmark
| | - Andreas T Sørensen
- Molecular Neuropharmacology and Genetics Laboratory, Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Maersk Tower 7.5, 2200 Copenhagen, Denmark
| | - Nicolai O Haahr
- Molecular Neuropharmacology and Genetics Laboratory, Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Maersk Tower 7.5, 2200 Copenhagen, Denmark
| | - Søren H Jørgensen
- Molecular Neuropharmacology and Genetics Laboratory, Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Maersk Tower 7.5, 2200 Copenhagen, Denmark
| | - Daryl A Guthrie
- Medicinal Chemistry Section, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse-Intramural Research Program, National Institutes of Health, Baltimore, MD 21224, USA
| | - Jonatan F Støier
- Molecular Neuropharmacology and Genetics Laboratory, Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Maersk Tower 7.5, 2200 Copenhagen, Denmark
| | - Christian Werner
- Department of Biotechnology and Biophysics, Biocenter, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Amy Hauck Newman
- Medicinal Chemistry Section, Molecular Targets and Medications Discovery Branch, National Institute on Drug Abuse-Intramural Research Program, National Institutes of Health, Baltimore, MD 21224, USA
| | - Markus Sauer
- Department of Biotechnology and Biophysics, Biocenter, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Freja Herborg
- Molecular Neuropharmacology and Genetics Laboratory, Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Maersk Tower 7.5, 2200 Copenhagen, Denmark
| | - Ulrik Gether
- Molecular Neuropharmacology and Genetics Laboratory, Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Maersk Tower 7.5, 2200 Copenhagen, Denmark.
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Joanna B, Michal K, Agnieszka WB, Katarzyna Z, Marzena M, Ryszard P, Wojciech S. Alpha-2A but not 2B/C noradrenergic receptors in ventral tegmental area regulate phasic dopamine release in nucleus accumbens core. Neuropharmacology 2022; 220:109258. [PMID: 36116534 DOI: 10.1016/j.neuropharm.2022.109258] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Revised: 09/09/2022] [Accepted: 09/11/2022] [Indexed: 11/20/2022]
Abstract
Adrenergic receptors (AR) in the ventral tegmental area (VTA) modulate local neuronal activity and, as a consequence, dopamine (DA) release in the mesolimbic forebrain. Such modulation has functional significance: intra-VTA blockade of α1-AR attenuates behavioral responses to salient environmental stimuli in rat models of drug seeking and conditioned fear as well as phasic DA release in the nucleus accumbens (NAc). In contrast, α2-AR in the VTA has been suggested to act primarily as autoreceptors, limiting local noradrenergic input. The regulation of noradrenaline efflux by α2-AR could be of clinical interest, as α2-AR agonists are proposed as promising pharmacological tools in the treatment of PTSD and substance use disorder. Thus, the aim of our study was to determine the subtype-specificity of α2-ARs in the VTA capable of modulating phasic DA release. We used fast scan cyclic voltammetry (FSCV) in anaesthetized male rats to measure DA release in the NAc after combined electrical stimulation and infusion of selected α2-AR antagonists into the VTA. Intra-VTA microinfusion of idazoxan - a non-subtype-specific α2-AR antagonist, as well as BRL-44408 - a selective α2A-AR antagonist, attenuated electrically-evoked DA in the NAc. In contrast, local administration of JP-1302 or imiloxan (α2B- and α2C-AR antagonists, respectively) had no effect. The effect of BRL-44408 on DA release was attenuated by intra-VTA DA D2 antagonist (raclopride) pre-administration. Finally, we confirmed the presence of α2A-AR protein in the VTA using western blotting. In conclusion, these data specify α2A-, but not α2B- or α2C-AR as the receptor subtype controlling NA release in the VTA.
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Affiliation(s)
- Bernacka Joanna
- Jagiellonian University, Institute of Applied Psychology, Department of Neurobiology and Neuropsychology, Łojasiewicza Str. 4, 30-348, Krakow, Poland; Maj Institute of Pharmacology, Polish Academy of Sciences, Department of Pharmacology, Laboratory of Pharmacology and Brain Biostructure, Smętna Str. 12, 31-343, Krakow, Poland
| | - Kielbinski Michal
- Jagiellonian University, Institute of Applied Psychology, Department of Neurobiology and Neuropsychology, Łojasiewicza Str. 4, 30-348, Krakow, Poland
| | - Wawrzczak-Bargieła Agnieszka
- Maj Institute of Pharmacology, Polish Academy of Sciences, Department of Pharmacology, Laboratory of Pharmacology and Brain Biostructure, Smętna Str. 12, 31-343, Krakow, Poland
| | - Zajda Katarzyna
- Jagiellonian University, Institute of Applied Psychology, Department of Neurobiology and Neuropsychology, Łojasiewicza Str. 4, 30-348, Krakow, Poland
| | - Maćkowiak Marzena
- Maj Institute of Pharmacology, Polish Academy of Sciences, Department of Pharmacology, Laboratory of Pharmacology and Brain Biostructure, Smętna Str. 12, 31-343, Krakow, Poland
| | - Przewlocki Ryszard
- Maj Institute of Pharmacology, Polish Academy of Sciences, Department of Molecular Neuropharmacology, Smętna Str. 12, 31-343, Krakow, Poland
| | - Solecki Wojciech
- Jagiellonian University, Institute of Applied Psychology, Department of Neurobiology and Neuropsychology, Łojasiewicza Str. 4, 30-348, Krakow, Poland.
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Chen R, Ferris MJ, Wang S. Dopamine D2 autoreceptor interactome: Targeting the receptor complex as a strategy for treatment of substance use disorder. Pharmacol Ther 2020; 213:107583. [PMID: 32473160 PMCID: PMC7434700 DOI: 10.1016/j.pharmthera.2020.107583] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2019] [Accepted: 05/11/2020] [Indexed: 02/06/2023]
Abstract
Dopamine D2 autoreceptors (D2ARs), located in somatodendritic and axon terminal compartments of dopamine (DA) neurons, function to provide a negative feedback regulatory control on DA neuron firing, DA synthesis, reuptake and release. Dysregulation of D2AR-mediated DA signaling is implicated in vulnerability to substance use disorder (SUD). Due to the extreme low abundance of D2ARs compared to postsynaptic D2 receptors (D2PRs) and the lack of experimental tools to differentiate the signaling of D2ARs from D2PRs, the regulation of D2ARs by drugs of abuse is poorly understood. The recent availability of conditional D2AR knockout mice and newly developed virus-mediated gene delivery approaches have provided means to specifically study the function of D2ARs at the molecular, cellular and behavioral levels. There is a growing revelation of novel mechanisms and new proteins that mediate D2AR activity, suggesting that D2ARs act cooperatively with an array of membrane and intracellular proteins to tightly control DA transmission. This review highlights D2AR-interacting partners including transporters, G-protein-coupled receptors, ion channels, intracellular signaling modulators, and protein kinases. The complexity of the D2AR interaction network illustrates the functional divergence of D2ARs. Pharmacological targeting of multiple D2AR-interacting partners may be more effective to restore disrupted DA homeostasis by drugs of abuse.
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Affiliation(s)
- Rong Chen
- Dept. of Physiology & Pharmacology, Wake Forest School of Medicine, Winston Salem, NC 27157, United States of America; Center for the Neurobiology of Addiction Treatment, Wake Forest School of Medicine, Winston Salem, NC 27157, United States of America.
| | - Mark J Ferris
- Dept. of Physiology & Pharmacology, Wake Forest School of Medicine, Winston Salem, NC 27157, United States of America; Center for the Neurobiology of Addiction Treatment, Wake Forest School of Medicine, Winston Salem, NC 27157, United States of America
| | - Shiyu Wang
- Dept. of Physiology & Pharmacology, Wake Forest School of Medicine, Winston Salem, NC 27157, United States of America
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Weber MA, Graack ET, Scholl JL, Renner KJ, Forster GL, Watt MJ. Enhanced dopamine D2 autoreceptor function in the adult prefrontal cortex contributes to dopamine hypoactivity following adolescent social stress. Eur J Neurosci 2018; 48:1833-1850. [PMID: 29904960 PMCID: PMC6105450 DOI: 10.1111/ejn.14019] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Revised: 05/22/2018] [Accepted: 06/06/2018] [Indexed: 11/28/2022]
Abstract
Adult psychiatric disorders characterized by cognitive deficits reliant on prefrontal cortex (PFC) dopamine are promoted by teenage bullying. Similarly, male Sprague-Dawley rats exposed to social defeat in mid-adolescence (P35-39) show impaired working memory in adulthood (P56-70), along with decreased medial PFC (mPFC) dopamine activity that results in part from increased dopamine transporter-mediated clearance. Here, we determined if dopamine synthesis and D2 autoreceptor-mediated inhibition of dopamine release in the adult mPFC are also enhanced by adolescent defeat to contribute to later dopamine hypofunction. Control and previously defeated rats did not differ in either DOPA accumulation following amino acid decarboxylase inhibition (NSD-1015 100 mg/kg ip.) or total/phosphorylated tyrosine hydroxylase protein expression, suggesting dopamine synthesis in the adult mPFC is not altered by adolescent defeat. However, exposure to adolescent defeat caused greater decreases in extracellular dopamine release (measured using in vivo chronoamperometry) in the adult mPFC upon local infusion of the D2 receptor agonist quinpirole (3 nM), implying greater D2 autoreceptor function. Equally enhanced D2 autoreceptor-mediated inhibition of dopamine release is seen in the adolescent (P40 or P49) mPFC, which declines in control rats by adulthood. However, this developmental decrease in autoreceptor function is absent following adolescent defeat, suggesting retention of an adolescent-like phenotype into adulthood. Current and previous findings indicate adolescent defeat decreases extracellular dopamine availability in the adult mPFC via both enhanced inhibition of dopamine release and increased dopamine clearance, which may be viable targets for improving treatment of cognitive deficits seen in neuropsychiatric disorders promoted by adolescent stress.
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Affiliation(s)
- Matthew A Weber
- Center for Brain and Behavior Research, Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, Vermillion, South Dakota
| | - Eric T Graack
- Center for Brain and Behavior Research, Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, Vermillion, South Dakota
| | - Jamie L Scholl
- Center for Brain and Behavior Research, Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, Vermillion, South Dakota
| | - Kenneth J Renner
- Center for Brain and Behavior Research, Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, Vermillion, South Dakota
- Department of Biology, University of South Dakota, Vermillion, South Dakota
| | - Gina L Forster
- Center for Brain and Behavior Research, Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, Vermillion, South Dakota
| | - Michael J Watt
- Center for Brain and Behavior Research, Basic Biomedical Sciences, Sanford School of Medicine, University of South Dakota, Vermillion, South Dakota
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Poetschke C, Dragicevic E, Duda J, Benkert J, Dougalis A, DeZio R, Snutch TP, Striessnig J, Liss B. Compensatory T-type Ca2+ channel activity alters D2-autoreceptor responses of Substantia nigra dopamine neurons from Cav1.3 L-type Ca2+ channel KO mice. Sci Rep 2015; 5:13688. [PMID: 26381090 PMCID: PMC4585382 DOI: 10.1038/srep13688] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Accepted: 08/03/2015] [Indexed: 12/17/2022] Open
Abstract
The preferential degeneration of Substantia nigra dopamine midbrain neurons (SN DA) causes the motor-symptoms of Parkinson's disease (PD). Voltage-gated L-type calcium channels (LTCCs), especially the Cav1.3-subtype, generate an activity-related oscillatory Ca(2+) burden in SN DA neurons, contributing to their degeneration and PD. While LTCC-blockers are already in clinical trials as PD-therapy, age-dependent functional roles of Cav1.3 LTCCs in SN DA neurons remain unclear. Thus, we analysed juvenile and adult Cav1.3-deficient mice with electrophysiological and molecular techniques. To unmask compensatory effects, we compared Cav1.3 KO mice with pharmacological LTCC-inhibition. LTCC-function was not necessary for SN DA pacemaker-activity at either age, but rather contributed to their pacemaker-precision. Moreover, juvenile Cav1.3 KO but not WT mice displayed adult wildtype-like, sensitised inhibitory dopamine-D2-autoreceptor (D2-AR) responses that depended upon both, interaction of the neuronal calcium sensor NCS-1 with D2-ARs, and on voltage-gated T-type calcium channel (TTCC) activity. This functional KO-phenotype was accompanied by cell-specific up-regulation of NCS-1 and Cav3.1-TTCC mRNA. Furthermore, in wildtype we identified an age-dependent switch of TTCC-function from contributing to SN DA pacemaker-precision in juveniles to pacemaker-frequency in adults. This novel interplay of Cav1.3 L-type and Cav3.1 T-type channels, and their modulation of SN DA activity-pattern and D2-AR-sensitisation, provide new insights into flexible age- and calcium-dependent activity-control of SN DA neurons and its pharmacological modulation.
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Affiliation(s)
| | - Elena Dragicevic
- Institute of Applied Physiology, University of Ulm, 89081 Ulm, Germany
| | - Johanna Duda
- Institute of Applied Physiology, University of Ulm, 89081 Ulm, Germany
| | - Julia Benkert
- Institute of Applied Physiology, University of Ulm, 89081 Ulm, Germany
| | - Antonios Dougalis
- Institute of Applied Physiology, University of Ulm, 89081 Ulm, Germany
| | - Roberta DeZio
- Institute of Applied Physiology, University of Ulm, 89081 Ulm, Germany
| | - Terrance P. Snutch
- Djavad Mowafaghian Centre for Brain and Health and Michael Smith Laboratories, University of British Columbia, V6T1Z4 Vancouver, Canada
| | - Joerg Striessnig
- Institute of Pharmacy, Department of Pharmacology and Toxicology, University of Innsbruck, 6020 Innsbruck, Austria
| | - Birgit Liss
- Institute of Applied Physiology, University of Ulm, 89081 Ulm, Germany
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Langer SZ. α2-Adrenoceptors in the treatment of major neuropsychiatric disorders. Trends Pharmacol Sci 2015; 36:196-202. [PMID: 25771972 DOI: 10.1016/j.tips.2015.02.006] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2014] [Revised: 02/07/2015] [Accepted: 02/13/2015] [Indexed: 12/16/2022]
Abstract
Presynaptic autoreceptors mediate a retrograde transfer of information by a negative feedback mechanism mediated by the transmitter of the neuron, and fulfill an autoregulatory function in neurotransmission in the peripheral and central nervous system (CNS). Starting with norepinephrine (NE), it was later reported that an autoreceptor-mediated negative feedback mechanism exists for other neurotransmitters, including dopamine (DA), serotonin, acetylcholine, histamine, GABA, and glutamate. This feedback mechanism regulates calcium-dependent transmitter release and synthesis through terminal presynaptic autoreceptors, while the firing rate of the neuron is regulated through somatodendritic autoreceptors.
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Affiliation(s)
- Salomon Z Langer
- Synaptic Pharma Ltd, 8 Herzel Rosenblum St Apt 4650, Tel Aviv 69379, Israel.
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McClure-Begley TD, Grady SR, Marks MJ, Collins AC, Stitzel JA. Presynaptic GABAB autoreceptor regulation of nicotinic acetylcholine receptor mediated [(3)H]-GABA release from mouse synaptosomes. Biochem Pharmacol 2014; 91:87-96. [PMID: 24953818 DOI: 10.1016/j.bcp.2014.06.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2014] [Revised: 06/06/2014] [Accepted: 06/12/2014] [Indexed: 01/26/2023]
Abstract
Activation of nicotinic acetylcholine receptors (nAChRs) can elicit neurotransmitter release from presynaptic nerve terminals. Mechanisms contributing to cell-and-terminal specific regulation of nAChR-mediated neurotransmitter exocytosis are not fully understood. The experiments discussed here examine how activation of GABAB auto- and hetero-receptors suppress nAChR-mediated release of [(3)H]-GABA and [(3)H]-dopamine ((3)H-DA) from mouse striatal synaptosomes. Activation of presynaptic GABAB receptors with (R)-baclofen decreased both [(3)H]-GABA and [(3)H]-DA release evoked by potassium depolarization. However, when nAChRs were activated with ACh to evoke neurotransmitter release, (R)-baclofen had no effect on [(3)H]-DA release, but potently inhibited ACh-evoked [(3)H]-GABA release. Inhibition of nAChR-evoked [(3)H]-GABA release by (R)-baclofen was time sensitive and the effect was lost after prolonged exposure to the GABAB agonist. The early inhibitory effect of GABAB activation on ACh-evoked [(3)H]-GABA release was partially attenuated by antagonists of the phosphatase, calcineurin. Furthermore, antagonists of protein kinase C (PKC) prevented the time-dependent loss of the inhibitory (R)-baclofen effect on [(3)H]-GABA release. These results suggest that α4β2*-nAChRs present on GABAergic nerve terminals in the striatum are subject to functional regulation by GABAB autoreceptors that is apparently cell-type specific, since it is absent from DAergic striatal nerve terminals. In addition, the functional modulation of α4β2*-type nAChRs on striatal GABAergic nerve terminals by GABAB autoreceptor activation is time-sensitive and appears to involve opposing actions of calcineurin and PKC.
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Affiliation(s)
- Tristan D McClure-Begley
- Institute for Behavioral Genetics, University of Colorado, Boulder, CO, United States of America; Department of Integrative Physiology, University of Colorado, Boulder, CO, United States of America; Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, CO, United States of America
| | - Sharon R Grady
- Institute for Behavioral Genetics, University of Colorado, Boulder, CO, United States of America
| | - Michael J Marks
- Institute for Behavioral Genetics, University of Colorado, Boulder, CO, United States of America; Department of Psychology and Neuroscience, University of Colorado, Boulder, CO, United States of America
| | - Allan C Collins
- Institute for Behavioral Genetics, University of Colorado, Boulder, CO, United States of America
| | - Jerry A Stitzel
- Institute for Behavioral Genetics, University of Colorado, Boulder, CO, United States of America; Department of Integrative Physiology, University of Colorado, Boulder, CO, United States of America.
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10
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Garcia-Garcia A, Tancredi AN, Leonardo ED. 5-HT(1A) [corrected] receptors in mood and anxiety: recent insights into autoreceptor versus heteroreceptor function. Psychopharmacology (Berl) 2014; 231:623-36. [PMID: 24337875 PMCID: PMC3927969 DOI: 10.1007/s00213-013-3389-x] [Citation(s) in RCA: 142] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Accepted: 11/26/2013] [Indexed: 11/26/2022]
Abstract
RATIONALE Serotonin (5-HT) neurotransmission is intimately linked to anxiety and depression and a diverse body of evidence supports the involvement of the main inhibitory serotonergic receptor, the serotonin-1A (5-HT(1A)) subtype, in both disorders. OBJECTIVES In this review, we examine the function of 5-HT(1A) receptor subpopulations and re-interpret our understanding of their role in mental illness in light of new data, separating both spatial (autoreceptor versus heteroreceptor) and the temporal (developmental versus adult) roles of the endogenous 5-HT(1A) receptors, emphasizing their distinct actions in mediating anxiety and depression-like behaviors. RESULTS It is difficult to unambiguously distinguish the effects of different populations of the 5-HT(1A) receptors with traditional genetic animal models and pharmacological approaches. However, with the advent of novel genetic systems and subpopulation-selective pharmacological agents, direct evidence for the distinct roles of these populations in governing emotion-related behavior is emerging. CONCLUSIONS There is strong and growing evidence for a functional dissociation between auto- and heteroreceptor populations in mediating anxiety and depressive-like behaviors, respectively. Furthermore, while it is well established that 5-HT(1A) receptors act developmentally to establish normal anxiety-like behaviors, the developmental role of 5-HT(1A) heteroreceptors is less clear, and the specific mechanisms underlying the developmental role of each subpopulation are likely to be key elements determining mood control in adult subjects.
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Affiliation(s)
- Alvaro Garcia-Garcia
- Department of Psychiatry, Division of Integrative Neuroscience, Columbia University and the New York State Psychiatric Institute, 1051 Riverside Dr. Box 87, New York, NY 10032
- Correspondence should be addressed to either AGG at or EDL at , Telephone: (001) 212-543-5266, Fax: (001) 212-543-5129
| | | | - E. David Leonardo
- Department of Psychiatry, Division of Integrative Neuroscience, Columbia University and the New York State Psychiatric Institute, 1051 Riverside Dr. Box 87, New York, NY 10032
- Correspondence should be addressed to either AGG at or EDL at , Telephone: (001) 212-543-5266, Fax: (001) 212-543-5129
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11
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González-González IM, Henley JM. Postsynaptic kainate receptor recycling and surface expression are regulated by metabotropic autoreceptor signalling. Traffic 2013; 14:810-22. [PMID: 23556457 PMCID: PMC3744763 DOI: 10.1111/tra.12071] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2012] [Revised: 04/02/2013] [Accepted: 04/04/2013] [Indexed: 01/01/2023]
Abstract
Kainate receptors (KARs) play fundamentally important roles in controlling synaptic function and regulating neuronal excitability. Postsynaptic KARs contribute to excitatory neurotransmission but the molecular mechanisms underlying their activity-dependent surface expression are not well understood. Strong activation of KARs in cultured hippocampal neurons leads to the downregulation of postsynaptic KARs via endocytosis and degradation. In contrast, low-level activation augments postsynaptic KAR surface expression. Here, we show that this increase in KARs is due to enhanced recycling via the recruitment of Rab11-dependent, transferrin-positive endosomes into spines. Dominant-negative Rab11 or the recycling inhibitor primaquine prevents the kainate-evoked increase in surface KARs. Moreover, we show that the increase in surface expression is mediated via a metabotropic KAR signalling pathway, which is blocked by the protein kinase C inhibitor chelerythrine, the calcium chelator BAPTA and the G-protein inhibitor pertussis toxin. Thus, we report a previously uncharacterized positive feedback system that increases postsynaptic KARs in response to low- or moderate-level agonist activation and can provide additional flexibility to synaptic regulation.
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Affiliation(s)
| | - Jeremy M Henley
- School of Biochemistry, University of Bristol, Medical Sciences Building, University WalkBristol, BS8 1TD, UK
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12
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Ferrés-Coy A, Pilar-Cuellar F, Vidal R, Paz V, Masana M, Cortés R, Carmona MC, Campa L, Pazos Á, Montefeltro A, Valdizán EM, Artigas F, Bortolozzi A. RNAi-mediated serotonin transporter suppression rapidly increases serotonergic neurotransmission and hippocampal neurogenesis. Transl Psychiatry 2013; 3:e211. [PMID: 23321808 PMCID: PMC3566716 DOI: 10.1038/tp.2012.135] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/24/2012] [Revised: 11/08/2012] [Accepted: 11/10/2012] [Indexed: 12/16/2022] Open
Abstract
Current antidepressants, which inhibit the serotonin transporter (SERT), display limited efficacy and slow onset of action. Here, we show that partial reduction of SERT expression by small interference RNA (SERT-siRNA) decreased immobility in the tail suspension test, displaying an antidepressant potential. Moreover, short-term SERT-siRNA treatment modified mouse brain variables considered to be key markers of antidepressant action: reduced expression and function of 5-HT(1A)-autoreceptors, elevated extracellular serotonin in forebrain and increased neurogenesis and expression of plasticity-related genes (BDNF, VEGF, Arc) in hippocampus. Remarkably, these effects occurred much earlier and were of greater magnitude than those evoked by long-term fluoxetine treatment. These findings highlight the critical role of SERT in serotonergic function and show that the reduction of SERT expression regulates serotonergic neurotransmission more potently than pharmacological blockade of SERT. The use of siRNA-targeting genes in serotonin neurons (SERT, 5-HT(1A)-autoreceptor) may be a novel therapeutic strategy to develop fast-acting antidepressants.
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MESH Headings
- Analysis of Variance
- Animals
- Antidepressive Agents/metabolism
- Antidepressive Agents/pharmacology
- Autoreceptors/genetics
- Autoreceptors/metabolism
- Brain-Derived Neurotrophic Factor/drug effects
- Brain-Derived Neurotrophic Factor/genetics
- Cytoskeletal Proteins/drug effects
- Cytoskeletal Proteins/genetics
- Fluoxetine/metabolism
- Fluoxetine/pharmacology
- Gene Expression
- Hippocampus/cytology
- Hippocampus/drug effects
- Hippocampus/metabolism
- Immunohistochemistry
- In Situ Hybridization
- Male
- Mice
- Mice, Inbred C57BL
- Nerve Tissue Proteins/drug effects
- Nerve Tissue Proteins/genetics
- Neurogenesis/genetics
- Neurogenesis/physiology
- RNA Interference/physiology
- RNA, Small Interfering/genetics
- RNA, Small Interfering/metabolism
- RNA, Small Interfering/pharmacology
- Receptor, Serotonin, 5-HT1A/drug effects
- Receptor, Serotonin, 5-HT1A/genetics
- Receptor, Serotonin, 5-HT1A/metabolism
- Serotonin Plasma Membrane Transport Proteins/genetics
- Serotonin Plasma Membrane Transport Proteins/metabolism
- Serotonin Plasma Membrane Transport Proteins/pharmacology
- Synaptic Transmission/drug effects
- Synaptic Transmission/genetics
- Vascular Endothelial Growth Factor A/drug effects
- Vascular Endothelial Growth Factor A/genetics
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Affiliation(s)
- A Ferrés-Coy
- Department of Neurochemistry and Neuropharmacology, IIBB-CSIC, IDIBAPS, Barcelona, Spain
- Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), ISCIII, Madrid, Spain
| | - F Pilar-Cuellar
- Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), ISCIII, Madrid, Spain
- Institute of Biomedicine and Biotechnology of Cantabria (IBBTEC; UC-CISC-SODERCAN), Santander, Spain
| | - R Vidal
- Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), ISCIII, Madrid, Spain
- Institute of Biomedicine and Biotechnology of Cantabria (IBBTEC; UC-CISC-SODERCAN), Santander, Spain
| | - V Paz
- Department of Neurochemistry and Neuropharmacology, IIBB-CSIC, IDIBAPS, Barcelona, Spain
- Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), ISCIII, Madrid, Spain
| | - M Masana
- Department of Neurochemistry and Neuropharmacology, IIBB-CSIC, IDIBAPS, Barcelona, Spain
- Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), ISCIII, Madrid, Spain
| | - R Cortés
- Department of Neurochemistry and Neuropharmacology, IIBB-CSIC, IDIBAPS, Barcelona, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas (CIBERNED), ISCIII, Madrid, Spain
| | | | - L Campa
- Department of Neurochemistry and Neuropharmacology, IIBB-CSIC, IDIBAPS, Barcelona, Spain
- Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), ISCIII, Madrid, Spain
| | - Á Pazos
- Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), ISCIII, Madrid, Spain
- Institute of Biomedicine and Biotechnology of Cantabria (IBBTEC; UC-CISC-SODERCAN), Santander, Spain
| | | | - E M Valdizán
- Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), ISCIII, Madrid, Spain
- Institute of Biomedicine and Biotechnology of Cantabria (IBBTEC; UC-CISC-SODERCAN), Santander, Spain
| | - F Artigas
- Department of Neurochemistry and Neuropharmacology, IIBB-CSIC, IDIBAPS, Barcelona, Spain
- Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), ISCIII, Madrid, Spain
| | - A Bortolozzi
- Department of Neurochemistry and Neuropharmacology, IIBB-CSIC, IDIBAPS, Barcelona, Spain
- Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), ISCIII, Madrid, Spain
- Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain
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13
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Czesak M, Le François B, Millar AM, Deria M, Daigle M, Visvader JE, Anisman H, Albert PR. Increased serotonin-1A (5-HT1A) autoreceptor expression and reduced raphe serotonin levels in deformed epidermal autoregulatory factor-1 (Deaf-1) gene knock-out mice. J Biol Chem 2012; 287:6615-27. [PMID: 22232550 PMCID: PMC3307310 DOI: 10.1074/jbc.m111.293027] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2011] [Revised: 12/23/2011] [Indexed: 02/02/2023] Open
Abstract
Altered regulation of the serotonin-1A (5-HT1A) receptor gene is implicated in major depression and mood disorders. The functional human 5-HT1A C(-1019)G promoter polymorphism (rs6295), which prevents the binding of Deaf-1/NUDR leading to dysregulation of the receptor, has been associated with major depression. In cell models Deaf-1 displays dual activity, repressing 5-HT1A autoreceptor expression in serotonergic raphe cells while enhancing postsynaptic 5-HT1A heteroreceptor expression in nonserotonergic neurons. A functional Deaf-1 binding site on the mouse 5-HT1A promoter was recognized by Deaf-1 in vitro and in vivo and mediated dual activity of Deaf-1 on 5-HT1A gene transcription. To address regulation by Deaf-1 in vivo, Deaf-1 knock-out mice bred to a C57BL/6 background were compared with wild-type siblings for changes in 5-HT1A RNA and protein by quantitative RT-PCR, in situ hybridization, and immunofluorescence. In the dorsal raphe, Deaf-1 knock-out mice displayed increased 5-HT1A mRNA, protein, and 5-HT1A-positive cell counts but reduced 5-HT levels, whereas other serotonergic markers, such as tryptophan hydroxylase (TPH)- or 5-HT-positive cells and TPH2 RNA levels, were unchanged. By contrast, 5-HT1A mRNA and 5-HT1A-positive cells were reduced in the frontal cortex of Deaf-1-null mice, with no significant change in hippocampal 5-HT1A RNA, protein, or cell counts. The region-specific alterations of brain 5-HT1A gene expression and reduced raphe 5-HT content in Deaf-1(-/-) mice indicate the importance of Deaf-1 in regulation of 5-HT1A gene expression and provide insight into the role of the 5-HT1A G(-1019) allele in reducing serotonergic neurotransmission by derepression of 5-HT1A autoreceptors.
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MESH Headings
- Animals
- Autoreceptors/genetics
- Autoreceptors/metabolism
- DNA-Binding Proteins
- Depressive Disorder/metabolism
- Depressive Disorder/physiopathology
- Female
- Fluorescent Antibody Technique
- Male
- Mice
- Mice, 129 Strain
- Mice, Inbred BALB C
- Mice, Inbred C57BL
- Mice, Knockout
- Polymorphism, Genetic/genetics
- Promoter Regions, Genetic/genetics
- RNA, Messenger/metabolism
- Raphe Nuclei/physiology
- Receptor, Serotonin, 5-HT1A/genetics
- Receptor, Serotonin, 5-HT1A/metabolism
- Serotonin/metabolism
- Transcription Factors/genetics
- Transcription Factors/metabolism
- Tryptophan Hydroxylase/genetics
- Tryptophan Hydroxylase/metabolism
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Affiliation(s)
- Margaret Czesak
- From the Ottawa Hospital Research Institute (Neuroscience), Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
| | - Brice Le François
- From the Ottawa Hospital Research Institute (Neuroscience), Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
| | - Anne M. Millar
- From the Ottawa Hospital Research Institute (Neuroscience), Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
| | - Mariam Deria
- From the Ottawa Hospital Research Institute (Neuroscience), Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
| | - Mireille Daigle
- From the Ottawa Hospital Research Institute (Neuroscience), Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
| | - Jane E. Visvader
- the Walter and Eliza Hall Institute of Medical Research, Melbourne, Victoria 3050, Australia, and
| | - Hymie Anisman
- the Institute of Neuroscience, Carleton University, Ottawa, Ontario K1S 5B6, Canada
| | - Paul R. Albert
- From the Ottawa Hospital Research Institute (Neuroscience), Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
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14
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Abstract
BACKGROUND Serotonin is a neurotransmitter that has been linked to a wide variety of behaviors including feeding and body-weight regulation, social hierarchies, aggression and suicidality, obsessive compulsive disorder, alcoholism, anxiety, and affective disorders. Full understanding of serotonergic systems in the central nervous system involves genomics, neurochemistry, electrophysiology, and behavior. Though associations have been found between functions at these different levels, in most cases the causal mechanisms are unknown. The scientific issues are daunting but important for human health because of the use of selective serotonin reuptake inhibitors and other pharmacological agents to treat disorders in the serotonergic signaling system. METHODS We construct a mathematical model of serotonin synthesis, release, and reuptake in a single serotonergic neuron terminal. The model includes the effects of autoreceptors, the transport of tryptophan into the terminal, and the metabolism of serotonin, as well as the dependence of release on the firing rate. The model is based on real physiology determined experimentally and is compared to experimental data. RESULTS We compare the variations in serotonin and dopamine synthesis due to meals and find that dopamine synthesis is insensitive to the availability of tyrosine but serotonin synthesis is sensitive to the availability of tryptophan. We conduct in silico experiments on the clearance of extracellular serotonin, normally and in the presence of fluoxetine, and compare to experimental data. We study the effects of various polymorphisms in the genes for the serotonin transporter and for tryptophan hydroxylase on synthesis, release, and reuptake. We find that, because of the homeostatic feedback mechanisms of the autoreceptors, the polymorphisms have smaller effects than one expects. We compute the expected steady concentrations of serotonin transporter knockout mice and compare to experimental data. Finally, we study how the properties of the the serotonin transporter and the autoreceptors give rise to the time courses of extracellular serotonin in various projection regions after a dose of fluoxetine. CONCLUSIONS Serotonergic systems must respond robustly to important biological signals, while at the same time maintaining homeostasis in the face of normal biological fluctuations in inputs, expression levels, and firing rates. This is accomplished through the cooperative effect of many different homeostatic mechanisms including special properties of the serotonin transporters and the serotonin autoreceptors. Many difficult questions remain in order to fully understand how serotonin biochemistry affects serotonin electrophysiology and vice versa, and how both are changed in the presence of selective serotonin reuptake inhibitors. Mathematical models are useful tools for investigating some of these questions.
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Affiliation(s)
- Janet Best
- Department of Mathematics, The Ohio State University, Columbus, OH 43210 USA
| | | | - Michael Reed
- Department of Mathematics, Duke University, Durham, NC 27708 USA
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15
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Der-Ghazarian T, Charntikov S, Varela FA, Crawford CA, McDougall SA. Effects of repeated and acute aripiprazole or haloperidol treatment on dopamine synthesis in the dorsal striatum of young rats: comparison to adult rats. J Neural Transm (Vienna) 2010; 117:573-83. [PMID: 20372943 DOI: 10.1007/s00702-010-0396-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2009] [Accepted: 03/17/2010] [Indexed: 11/30/2022]
Abstract
The purpose of the present study was to determine whether repeated treatment with the D2 partial agonist aripiprazole or the D2 antagonist haloperidol alters dopamine (DA) synthesis characteristics in the dorsal striatum of young rats. To this end, rats received a daily pretreatment regimen of aripiprazole or haloperidol on postnatal days (PD) 10-20 and were tested 24 or 72 h later after an acute injection of vehicle, aripiprazole, haloperidol, or quinpirole (a D2 agonist). For comparison purposes, adult rats were pretreated with an 11-day regimen of saline or haloperidol on PD 70-80 and DA synthesis was measured after acute drug treatment on PD 83. Dorsal striatal DA synthesis was determined by measuring L-dihydroxyphenylalanine accumulation after NSD-1015 treatment. In a separate experiment, the ability of repeated drug treatment to up-regulate dorsal striatal D2 receptors was assessed in young and adult rats 72 h after drug discontinuation. The major findings of this study were that: (a) acute treatment with haloperidol and aripiprazole increased DA synthesis while quinpirole reduced it; (b) pretreatment with haloperidol and aripiprazole blunted the synthesis-modulating effects of acutely administered dopaminergic drugs; and (c) DA synthesis of young and adult rats was affected in a qualitatively similar manner by DA agonist, antagonist, and partial agonist drugs. In conclusion, results from the present study suggest that synthesis-modulating autoreceptors in the dorsal striatum are functionally mature by the end of the preweanling period and DA synthesis declines to near basal levels during the course of repeated aripiprazole treatment.
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Affiliation(s)
- Taleen Der-Ghazarian
- Department of Psychology, California State University San Bernardino, 5500 University Parkway, San Bernardino, CA 92407, USA
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16
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Richardson-Jones JW, Craige CP, Guiard BP, Stephen A, Metzger KL, Kung HF, Gardier AM, Dranovsky A, David DJ, Beck SG, Hen R, Leonardo ED. 5-HT1A autoreceptor levels determine vulnerability to stress and response to antidepressants. Neuron 2010; 65:40-52. [PMID: 20152112 PMCID: PMC2941196 DOI: 10.1016/j.neuron.2009.12.003] [Citation(s) in RCA: 314] [Impact Index Per Article: 22.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/13/2009] [Indexed: 12/28/2022]
Abstract
Most depressed patients don't respond to their first drug treatment, and the reasons for this treatment resistance remain enigmatic. Human studies implicate a polymorphism in the promoter of the serotonin-1A (5-HT(1A)) receptor gene in increased susceptibility to depression and decreased treatment response. Here we develop a new strategy to manipulate 5-HT(1A) autoreceptors in raphe nuclei without affecting 5-HT(1A) heteroreceptors, generating mice with higher (1A-High) or lower (1A-Low) autoreceptor levels. We show that this robustly affects raphe firing rates, but has no effect on either basal forebrain serotonin levels or conflict-anxiety measures. However, compared to 1A-Low mice, 1A-High mice show a blunted physiological response to acute stress, increased behavioral despair, and no behavioral response to antidepressant, modeling patients with the 5-HT(1A) risk allele. Furthermore, reducing 5-HT(1A) autoreceptor levels prior to antidepressant treatment is sufficient to convert nonresponders into responders. These results establish a causal relationship between 5-HT(1A) autoreceptor levels, resilience under stress, and response to antidepressants.
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17
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Lanquar V, Loqué D, Hörmann F, Yuan L, Bohner A, Engelsberger WR, Lalonde S, Schulze WX, von Wirén N, Frommer WB. Feedback inhibition of ammonium uptake by a phospho-dependent allosteric mechanism in Arabidopsis. Plant Cell 2009; 21:3610-22. [PMID: 19948793 PMCID: PMC2798313 DOI: 10.1105/tpc.109.068593] [Citation(s) in RCA: 133] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2009] [Revised: 09/23/2009] [Accepted: 11/06/2009] [Indexed: 05/18/2023]
Abstract
The acquisition of nutrients requires tight regulation to ensure optimal supply while preventing accumulation to toxic levels. Ammonium transporter/methylamine permease/rhesus (AMT/Mep/Rh) transporters are responsible for ammonium acquisition in bacteria, fungi, and plants. The ammonium transporter AMT1;1 from Arabidopsis thaliana uses a novel regulatory mechanism requiring the productive interaction between a trimer of subunits for function. Allosteric regulation is mediated by a cytosolic C-terminal trans-activation domain, which carries a conserved Thr (T460) in a critical position in the hinge region of the C terminus. When expressed in yeast, mutation of T460 leads to inactivation of the trimeric complex. This study shows that phosphorylation of T460 is triggered by ammonium in a time- and concentration-dependent manner. Neither Gln nor l-methionine sulfoximine-induced ammonium accumulation were effective in inducing phosphorylation, suggesting that roots use either the ammonium transporter itself or another extracellular sensor to measure ammonium concentrations in the rhizosphere. Phosphorylation of T460 in response to an increase in external ammonium correlates with inhibition of ammonium uptake into Arabidopsis roots. Thus, phosphorylation appears to function in a feedback loop restricting ammonium uptake. This novel autoregulatory mechanism is capable of tuning uptake capacity over a wide range of supply levels using an extracellular sensory system, potentially mediated by a transceptor (i.e., transporter and receptor).
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Affiliation(s)
- Viviane Lanquar
- Department of Plant Biology, Carnegie Institution for Science, Stanford, California 94305
| | - Dominique Loqué
- Department of Plant Biology, Carnegie Institution for Science, Stanford, California 94305
| | - Friederike Hörmann
- Department of Plant Biology, Carnegie Institution for Science, Stanford, California 94305
| | - Lixing Yuan
- Key Lab of Plant Nutrition, College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China
| | - Anne Bohner
- Molecular Plant Nutrition, Leibniz-Institute for Plant Genetics and Crop Plant Research, 06466 Gatersleben, Germany
| | | | - Sylvie Lalonde
- Department of Plant Biology, Carnegie Institution for Science, Stanford, California 94305
| | | | - Nicolaus von Wirén
- Molecular Plant Nutrition, Leibniz-Institute for Plant Genetics and Crop Plant Research, 06466 Gatersleben, Germany
| | - Wolf B. Frommer
- Department of Plant Biology, Carnegie Institution for Science, Stanford, California 94305
- Address correspondence to
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18
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Abstract
BACKGROUND Dopamine is a catecholamine that is used as a neurotransmitter both in the periphery and in the central nervous system. Dysfunction in various dopaminergic systems is known to be associated with various disorders, including schizophrenia, Parkinson's disease, and Tourette's syndrome. Furthermore, microdialysis studies have shown that addictive drugs increase extracellular dopamine and brain imaging has shown a correlation between euphoria and psycho-stimulant-induced increases in extracellular dopamine 1. These consequences of dopamine dysfunction indicate the importance of maintaining dopamine functionality through homeostatic mechanisms that have been attributed to the delicate balance between synthesis, storage, release, metabolism, and reuptake. METHODS We construct a mathematical model of dopamine synthesis, release, and reuptake and use it to study homeostasis in single dopaminergic neuron terminals. We investigate the substrate inhibition of tyrosine hydroxylase by tyrosine, the consequences of the rapid uptake of extracellular dopamine by the dopamine transporters, and the effects of the autoreceoptors on dopaminergic function. The main focus is to understand the regulation and control of synthesis and release and to explicate and interpret experimental findings. RESULTS We show that the substrate inhibition of tyrosine hydroxylase by tyrosine stabilizes cytosolic and vesicular dopamine against changes in tyrosine availability due to meals. We find that the autoreceptors dampen the fluctuations in extracellular dopamine caused by changes in tyrosine hydroxylase expression and changes in the rate of firing. We show that short bursts of action potentials create significant dopamine signals against the background of tonic firing. We explain the observed time courses of extracellular dopamine responses to stimulation in wild type mice and mice that have genetically altered dopamine transporter densities and the observed half-lives of extracellular dopamine under various treatment protocols. CONCLUSION Dopaminergic systems must respond robustly to important biological signals such as bursts, while at the same time maintaining homeostasis in the face of normal biological fluctuations in inputs, expression levels, and firing rates. This is accomplished through the cooperative effect of many different homeostatic mechanisms including special properties of tyrosine hydroxylase, the dopamine transporters, and the dopamine autoreceptors.
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Affiliation(s)
- Janet A Best
- Department of Mathematics, The Ohio State University, Columbus, OH 43210, USA
| | | | - Michael C Reed
- Department of Mathematics, Duke University, Durham, NC 27708, USA
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19
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Liu J, Rasul I, Sun Y, Wu G, Li L, Premont RT, Suo WZ. GRK5 deficiency leads to reduced hippocampal acetylcholine level via impaired presynaptic M2/M4 autoreceptor desensitization. J Biol Chem 2009; 284:19564-71. [PMID: 19478075 PMCID: PMC2740582 DOI: 10.1074/jbc.m109.005959] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2009] [Indexed: 11/06/2022] Open
Abstract
G protein-coupled receptor kinase 5 (GRK5) deficiency has been linked recently to early Alzheimer disease (AD), but the mechanism by which GRK5 deficiency may contribute to AD pathogenesis remains elusive. Here we report that overexpression of dominant negative mutant of GRK5 (dnGRK5) in a cholinergic neuronal cell line led to decreased acetylcholine (ACh) release. This reduction was fully corrected by pertussis toxin, atropine (a nonselective muscarinic antagonist), or methoctramine (a selective M2/M4 muscarinic receptor antagonist). Consistent with results in cultured cells, high potassium-evoked ACh release in hippocampal slices from young GRK5 knock-out mice was significantly reduced compared with wild type littermates, and this reduced ACh release was also fully corrected by methoctramine. In addition, following treatment with the nonselective muscarinic agonist oxotremorine-M, M2, and M4 receptors underwent significantly reduced internalization in GRK5KO slices compared with wild type slices, as assessed by plasma membrane retention of receptor immunoreactivity, whereas M1 receptor internalization was not affected by loss of GRK5 expression. Moreover, Western blotting revealed no synaptic or cholinergic degenerative changes in young GRK5 knock-out mice. Altogether, these results suggest that GRK5 deficiency leads to a reduced hippocampal ACh release and cholinergic hypofunction by selective impairment of desensitization of presynaptic M2/M4 autoreceptors. Because this nonstructural cholinergic hypofunction precedes the hippocampal cholinergic hypofunction associated with structural cholinergic degeneration and cognitive decline in aged GRK5 knock-out mice, this nonstructural alteration may be an early event contributing to cholinergic degeneration in AD.
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Affiliation(s)
- Jun Liu
- From the Laboratory for Alzheimer's Disease and Aging Research, Kansas City Veterans Affairs Medical Center, Kansas City, Missouri 64128
- the Department of Neurology, the Second Affiliated Hospital, Sun Yat-sen University, Guangzhou, Guangdong 510120, China
| | - Imtiaz Rasul
- From the Laboratory for Alzheimer's Disease and Aging Research, Kansas City Veterans Affairs Medical Center, Kansas City, Missouri 64128
| | - Yuning Sun
- From the Laboratory for Alzheimer's Disease and Aging Research, Kansas City Veterans Affairs Medical Center, Kansas City, Missouri 64128
- the Department of Biochemistry and Molecular Biology, Ningxia Medical University, Yinchuan, Ningxia 750004, China, and
| | - Guisheng Wu
- From the Laboratory for Alzheimer's Disease and Aging Research, Kansas City Veterans Affairs Medical Center, Kansas City, Missouri 64128
| | - Longxuan Li
- From the Laboratory for Alzheimer's Disease and Aging Research, Kansas City Veterans Affairs Medical Center, Kansas City, Missouri 64128
- the Department of Neurology, Guangdong Medical College Affiliated Hospital, Zhanjian, Guangdong 524001, China
| | - Richard T. Premont
- the Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710
| | - William Z. Suo
- From the Laboratory for Alzheimer's Disease and Aging Research, Kansas City Veterans Affairs Medical Center, Kansas City, Missouri 64128
- the Departments of Neurology and Physiology, University of Kansas Medical College, Kansas City, Kansas 66170
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20
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Abstract
Serotonergic dysfunction is present in mood disorders and suicide. Brainstem 5-HT1A somatodendritic autoreceptors regulate serotonin neuron firing but studies of autoreceptor binding in the dorsal raphe nucleus (DRN) in depressed suicides report conflicting results. We sought to determine: (1) the anatomical distribution of 5-HT1A receptor binding in the DRN in depressed suicides and psychiatrically normal controls; and (2) whether sex differences in 5-HT1A binding in the DRN contribute to differences between depressed suicides and controls. Previously collected quantitative receptor autoradiograms of [3H]8-hydroxy-2-(di-n-propyl)aminotetralin (3H-8-OH-DPAT) in postmortem tissue sections containing the DRN from drug-free suicide victims (n=10) and matched controls (n=10) were analyzed. Less total receptor binding (fmol/mg tissuexmm3) was observed in the entire DRN in depressed suicides compared with controls (p<0.05). Group differences along the rostrocaudal extent of the DRN were observed for cross-sectional 5-HT(1A) binding (fmol/mg tissue) and receptor binding (fmol/mgxmm3, p<0.05). Cross-sectional 5-HT1A DRN binding in depressed suicides compared with controls was higher rostrally and lower caudally. The differences between depressed suicides and controls were present in males and females, although females had more binding than males. Less autoreceptor binding in the DRN of depressed suicides may represent a homeostatic response to less serotonin release, increasing serotonin neuron firing. More autoreceptor binding in rostral DRN might contribute to deficient serotonin release in ventromedial prefrontal cortex by lower neuronal firing.
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Affiliation(s)
- Maura Boldrini
- Department of Psychiatry, Division of Neuroscience, Columbia University College of Physicians and Surgeons, New York State Psychiatric Institute, 1051 Riverside Drive, P.O. Box 42, New York, NY 10032, USA
- Department of Neurological and Psychiatric Sciences, University of Florence, Viale Morgagni 85, 50134 Firenze, Italy
| | - Mark D. Underwood
- Department of Psychiatry, Division of Neuroscience, Columbia University College of Physicians and Surgeons, New York State Psychiatric Institute, 1051 Riverside Drive, P.O. Box 42, New York, NY 10032, USA
| | - J. John Mann
- Department of Psychiatry, Division of Neuroscience, Columbia University College of Physicians and Surgeons, New York State Psychiatric Institute, 1051 Riverside Drive, P.O. Box 42, New York, NY 10032, USA
| | - Victoria Arango
- Department of Psychiatry, Division of Neuroscience, Columbia University College of Physicians and Surgeons, New York State Psychiatric Institute, 1051 Riverside Drive, P.O. Box 42, New York, NY 10032, USA
- *Corresponding author. Tel.: +1 212 543 5440; fax: +1 212 543 6017. E-mail address: (V. Arango)
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21
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Abstract
Glutamate and GABA, the two most abundant neurotransmitters in the mammalian central nervous system, can act on metabotropic receptors that are structurally quite dissimilar from those targeted by most other neurotransmitters/modulators. Accordingly, metabotropic glutamate receptors (mGluRs) and GABA(B) receptors (GABA(B)Rs) are classified as members of family 3 (or family C) of G protein-coupled receptors. On the other hand, mGluRs and GABA(B)Rs exhibit pronounced and partly unresolved differences between each other. The most intriguing difference is that mGluRs exist as multiple pharmacologically as well as structurally distinct subtypes, whereas, in the case of GABA(B)Rs, molecular biologists have so far identified only one structurally distinct heterodimeric complex whose few variants seem unable to explain the pharmacological heterogeneity of GABA(B)Rs observed in many functional studies. Both mGluRs and GABA(B)Rs can be localized on axon terminals of different neuronal systems as presynaptic autoreceptors and heteroreceptors modulating the exocytosis of various transmitters.
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Affiliation(s)
- M Raiteri
- Department of Experimental Medicine, Pharmacology and Toxicology Section, University of Genoa, 16148 Genoa, Italy.
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22
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Abstract
The serotonin 5-HT(1A) receptor is implicated in the pathophysiology of major neuropsychiatric disorders, including depression, suicidal behavior, panic disorder, epilepsy, bulimia, schizophrenia, Parkinson's disease, and Alzheimer's disease and is, therefore, an important target for drug therapy. 5-HT(1A) receptors are expressed as somatodendritic autoreceptors in serotonin neurons of the raphé nuclei (presynaptic) and as postsynaptic receptors in cortical and subcortical serotonin terminal fields in the brain. Due to the higher concentration and heterogeneous distribution of this receptor, it is an attractive target for quantification in vivo using positron emission tomography (PET) and single photon emission tomography (SPECT). Here, we review the PET radioligands employed for imaging 5-HT(1A) receptors in living brain.
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Affiliation(s)
- J S Dileep Kumar
- Department of Psychiatry, Columbia University College of Physicians and Surgeons & New York State Psychiatric Institute, New York, NY 10032, United States.
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23
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Pinheiro PS, Perrais D, Coussen F, Barhanin J, Bettler B, Mann JR, Malva JO, Heinemann SF, Mulle C. GluR7 is an essential subunit of presynaptic kainate autoreceptors at hippocampal mossy fiber synapses. Proc Natl Acad Sci U S A 2007; 104:12181-6. [PMID: 17620617 PMCID: PMC1924597 DOI: 10.1073/pnas.0608891104] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2006] [Indexed: 01/25/2023] Open
Abstract
Presynaptic ionotropic glutamate receptors are emerging as key players in the regulation of synaptic transmission. Here we identify GluR7, a kainate receptor (KAR) subunit with no known function in the brain, as an essential subunit of presynaptic autoreceptors that facilitate hippocampal mossy fiber synaptic transmission. GluR7(-/-) mice display markedly reduced short- and long-term synaptic potentiation. Our data suggest that presynaptic KARs are GluR6/GluR7 heteromers that coassemble and are localized within synapses. We show that recombinant GluR6/GluR7 KARs exhibit low sensitivity to glutamate, and we provide evidence that presynaptic KARs at mossy fiber synapses are likely activated by high concentrations of glutamate. Overall, from our data, we propose a model whereby presynaptic KARs are localized in the presynaptic active zone close to release sites, display low affinity for glutamate, are likely Ca(2+)-permeable, are activated by single release events, and operate within a short time window to facilitate the subsequent release of glutamate.
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Affiliation(s)
- Paulo S. Pinheiro
- *Laboratoire “Physiologie Cellulaire de la Synapse,” Centre National de la Recherche Scientifique, Bordeaux Neuroscience Institute, University of Bordeaux, 33077 Bordeaux Cedex, France
- Center for Neuroscience and Cell Biology of Coimbra, Institute of Biochemistry, Faculty of Medicine, University of Coimbra, 3004-504 Coimbra, Portugal
| | - David Perrais
- *Laboratoire “Physiologie Cellulaire de la Synapse,” Centre National de la Recherche Scientifique, Bordeaux Neuroscience Institute, University of Bordeaux, 33077 Bordeaux Cedex, France
| | - Françoise Coussen
- *Laboratoire “Physiologie Cellulaire de la Synapse,” Centre National de la Recherche Scientifique, Bordeaux Neuroscience Institute, University of Bordeaux, 33077 Bordeaux Cedex, France
| | - Jacques Barhanin
- Molecular Neurobiology Laboratory, The Salk Institute for Biological Studies, La Jolla, CA 92037; and
| | - Bernhard Bettler
- Molecular Neurobiology Laboratory, The Salk Institute for Biological Studies, La Jolla, CA 92037; and
| | - Jeffrey R. Mann
- Division of Biology, Beckman Research Institute, City of Hope, Duarte, CA 91010
| | - João O. Malva
- Center for Neuroscience and Cell Biology of Coimbra, Institute of Biochemistry, Faculty of Medicine, University of Coimbra, 3004-504 Coimbra, Portugal
| | - Stephen F. Heinemann
- Molecular Neurobiology Laboratory, The Salk Institute for Biological Studies, La Jolla, CA 92037; and
| | - Christophe Mulle
- *Laboratoire “Physiologie Cellulaire de la Synapse,” Centre National de la Recherche Scientifique, Bordeaux Neuroscience Institute, University of Bordeaux, 33077 Bordeaux Cedex, France
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24
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Gartside SE, Cole AJ, Williams AP, McQuade R, Judge SJ. AMPA and NMDA receptor regulation of firing activity in 5-HT neurons of the dorsal and median raphe nuclei. Eur J Neurosci 2007; 25:3001-8. [PMID: 17509083 DOI: 10.1111/j.1460-9568.2007.05577.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The glutamatergic regulation of 5-hydroxytryptamine (5-HT) neuronal activity has not been extensively studied. Here, we used extracellular single unit recording in midbrain slices to examine glutamate receptor mediated effects on 5-HT neuronal activity in the dorsal raphe nucleus (DRN) and the median raphe nucleus (MRN). Alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA; 1 and 3 microm) concentration-dependently increased firing in 5-HT neurons in both the DRN and the MRN. The response to AMPA was blocked by the AMPA receptor antagonist, 6,7-dinitroquinoxaline-2,3(1H-4H)-dione (DNQX; 10 microm) but not the N-methyl-d-aspartate (NMDA) receptor antagonist, 2-amino-5-phosphonopentanoic acid (AP-5; 50 microm). NMDA (10-100 microm) also increased 5-HT neuronal firing in a concentration-dependent manner in both the DRN and MRN; a response that was blocked by AP-5 (50 microm). In some DRN neurons the NMDA response was partially antagonized by DNQX (10 microm) suggesting that NMDA, as well as directly activating 5-HT neurons, evokes local release of glutamate, which indirectly activates AMPA receptors on 5-HT neurons. Responses of DRN 5-HT neurons to AMPA and NMDA were enhanced by the gamma-amino-butyric acid (GABA)(A) receptor antagonist, bicuculline (50 microm), suggesting that both AMPA and NMDA increase local release of GABA. Finally in the DRN the 5-HT(1A) receptor antagonist, WAY100635 (100 nm), failed to enhance the response of 5-HT neurons to AMPA and caused only a small increase in the excitatory response to NMDA suggesting a low degree of tonic activation of 5-HT(1A) autoreceptors even when 5-HT neuronal firing rate is high.
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Affiliation(s)
- S E Gartside
- Psychobiology Research Group, School of Neurology, Neurobiology and Psychiatry, The Medical School, University of Newcastle upon Tyne, UK.
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25
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Bortolozzi A, Díaz-Mataix L, Toth M, Celada P, Artigas F. In vivo actions of aripiprazole on serotonergic and dopaminergic systems in rodent brain. Psychopharmacology (Berl) 2007; 191:745-58. [PMID: 17265076 DOI: 10.1007/s00213-007-0698-y] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/16/2006] [Accepted: 12/28/2006] [Indexed: 01/30/2023]
Abstract
RATIONALE Aripiprazole is an atypical antipsychotic drug with high in vitro affinity for 5-HT(1A), 5-HT(2A) and dopamine (DA) D2 receptors. However, its in vivo actions in the brain are still poorly characterized. OBJECTIVE The aim was to study the in vivo actions of aripiprazole in the rat and mouse brain. METHODS Brain microdialysis and single-unit extracellular recordings were performed. RESULTS The systemic administration of aripiprazole reduced 5-HT output in the medial prefrontal cortex (mPFC) and dorsal raphe nucleus of the rat. Aripiprazole also reduced extracellular 5-HT in the mPFC of wild-type (WT) but not of 5-HT(1A) (-/-) knockout (KO) mice. Aripiprazole reversed the elevation in extracellular 5-HT output produced by the local application of the 5-HT(2A/2C) receptor agonist DOI in mPFC. Aripiprazole also increased the DA output in mPFC of WT but not of 5-HT(1A) KO mice, as observed for atypical antipsychotic drugs, in contrast to haloperidol. Contrary to haloperidol, which increases the firing rate of DA neurons in the ventral tegmental area (VTA), aripiprazole induced a very moderate reduction in dopaminergic activity. Haloperidol fully reversed the inhibition in dopaminergic firing rate induced by apomorphine, whereas aripiprazole evoked a partial reversal that was significantly different from that evoked by haloperidol and from the spontaneous reversal of dopaminergic activity in rats treated with apomorphine. CONCLUSIONS These results indicate that aripiprazole modulates the in vivo 5-HT and DA release in mPFC through the activation of 5-HT(1A) receptors. Moreover, aripiprazole behaves as a partial agonist at DA D2 autoreceptors in vivo, an action which clearly distinguishes it from haloperidol.
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MESH Headings
- Action Potentials/drug effects
- Animals
- Antipsychotic Agents/pharmacology
- Aripiprazole
- Autoreceptors/drug effects
- Autoreceptors/metabolism
- Brain/cytology
- Brain/drug effects
- Brain/metabolism
- Dopamine/metabolism
- Dopamine Agonists/pharmacology
- Dopamine Antagonists/pharmacology
- Haloperidol/pharmacology
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Microdialysis
- Piperazines/pharmacology
- Prefrontal Cortex/drug effects
- Prefrontal Cortex/metabolism
- Quinolones/pharmacology
- Raphe Nuclei/drug effects
- Raphe Nuclei/metabolism
- Rats
- Rats, Wistar
- Receptor, Serotonin, 5-HT1A/drug effects
- Receptor, Serotonin, 5-HT1A/genetics
- Receptor, Serotonin, 5-HT1A/metabolism
- Receptor, Serotonin, 5-HT2A/drug effects
- Receptor, Serotonin, 5-HT2A/metabolism
- Receptor, Serotonin, 5-HT2C/drug effects
- Receptor, Serotonin, 5-HT2C/metabolism
- Receptors, Dopamine D2/drug effects
- Receptors, Dopamine D2/metabolism
- Serotonin/metabolism
- Serotonin Receptor Agonists/pharmacology
- Ventral Tegmental Area/drug effects
- Ventral Tegmental Area/metabolism
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Affiliation(s)
- A Bortolozzi
- Department of Neurochemistry, Institut d' Investigacions Biomèdiques de Barcelona (CSIC), IDIBAPS, Rosselló, 161, 6th floor, 08036, Barcelona, Spain
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26
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Cahir M, Ardis T, Reynolds GP, Cooper SJ. Acute and chronic tryptophan depletion differentially regulate central 5-HT1A and 5-HT 2A receptor binding in the rat. Psychopharmacology (Berl) 2007; 190:497-506. [PMID: 17124620 DOI: 10.1007/s00213-006-0635-5] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/31/2006] [Accepted: 10/31/2006] [Indexed: 10/23/2022]
Abstract
RATIONALE Tryptophan depletion is used to reduce central serotonergic function and to investigate its role in psychiatric illness. Despite widespread clinical use, its effects on serotonin (5-HT) receptors have not been well characterized. OBJECTIVE The aim of this study was to examine the effect of acute (ATD) and chronic tryptophan depletion (CTD) on free-plasma tryptophan (TRP), central TRP and 5-HT and brain 5-HT(1A) and 5-HT(2A) receptor binding in the rat. METHODS TRP and 5-HT were measured by high-performance liquid chromatography and receptor levels determined by homogenate radioligand binding and in-vitro receptor autoradiography. RESULTS Free-plasma TRP, central TRP and central 5-HT levels were significantly and similarly reduced by ATD and 1- and 3-week CTD compared to controls. ATD significantly reduced 5-HT(1A) binding in the dorsal raphe (14%) but did not significantly alter postsynaptic 5-HT(1A) binding (frontal cortex, remaining cortex and hippocampus) or 5-HT(2A) binding (cortex and striatum). One-week CTD did not significantly alter cortical 5-HT(2A) binding or postsynaptic 5-HT(1A) binding. Furthermore, 3-week CTD did not significantly alter 5-HT(1A) binding but significantly increased cortical 5-HT(2A) binding without affecting striatal or hippocampal levels. In the CTD 1 and 3-week groups, rat body weight was significantly decreased as compared to controls. However, weight loss was not a confounding factor for decreased cortical 5-HT(2A)-receptor binding. CONCLUSION ATD-induced reduction in somatodendritic 5-HT(1A) autoreceptor binding may represent an intrinsic 'homeostatic response' reducing serotonergic feedback in dorsal raphe projection areas. In contrast, the increase in 5-HT(2A) receptor after CTD may be a compensatory response to a long-term reduction in 5-HT.
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Affiliation(s)
- Marie Cahir
- Division of Psychiatry and Neuroscience, Queen's University Belfast, Whitla, 97 Lisburn Road, Northern Ireland, UK.
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27
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Nassery K, Marino V, Parker DAS. Uptake and release of [(3)H]GABA in human dental pulp. Arch Oral Biol 2007; 52:607-13. [PMID: 17276385 DOI: 10.1016/j.archoralbio.2006.12.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2006] [Revised: 11/14/2006] [Accepted: 12/06/2006] [Indexed: 11/24/2022]
Abstract
The purpose of this study was to determine whether (a) an uptake system for gamma-aminobutyric acid (GABA) exists in human dental pulp, (b) GABA can be released from nerves in this tissue, and (c) GABA(B) autoreceptors modulate release of this transmitter. Segments of vital pulp were incubated in [(3)H]GABA (0.1-10 microM) for up to 120 min, washed, and the retained [(3)H] extracted and assayed. Some tissues were treated with GABA uptake inhibitors (nipecotic acid or NO-711) prior to incubation. At concentrations of 0.1 and 1.0 microM the uptake of [(3)H]GABA was saturated after 90 min of incubation. At 10 microM, at least two uptake compartments were apparent, and the amount of [(3)H]GABA retained was five-fold greater than 0.1 microM. The uptake inhibitors reduced [(3)H]GABA accumulation by more than 80%. In the release study, pulp was incubated in [(3)H]GABA (0.5 microM) for 90 min, and superfused with Krebs solution containing NO-711 (5 microM). Electrical stimulation increased the overflow of [(3)H]; a GABA(B) autoreceptor agonist (baclofen) inhibited, whilst an antagonist, Sch 50911, enhanced this release. The effects of baclofen were reversed by Sch 50911. These results imply that GABA can be taken up and bound firmly in compartments within human dental pulp, GABA can be released from isolated pulp segments by electrical stimulation, and this release is modulated by GABA(B) autoreceptors.
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Affiliation(s)
- Khashayar Nassery
- School of Dentistry, The University of Adelaide University, Adelaide, South Australia 5005, Australia
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28
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Müller CP, Carey RJ, Huston JP, De Souza Silva MA. Serotonin and psychostimulant addiction: Focus on 5-HT1A-receptors. Prog Neurobiol 2007; 81:133-78. [PMID: 17316955 DOI: 10.1016/j.pneurobio.2007.01.001] [Citation(s) in RCA: 232] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2006] [Revised: 12/04/2006] [Accepted: 01/03/2007] [Indexed: 01/03/2023]
Abstract
Serotonin(1A)-receptors (5-HT(1A)-Rs) are important components of the 5-HT system in the brain. As somatodendritic autoreceptors they control the activity of 5-HT neurons, and, as postsynaptic receptors, the activity in terminal areas. Cocaine (COC), amphetamine (AMPH), methamphetamine (METH) and 3,4-methylenedioxymethamphetamine ("Ecstasy", MDMA) are psychostimulant drugs that can lead to addiction-related behavior in humans and in animals. At the neurochemical level, these psychostimulant drugs interact with monoamine transporters and increase extracellular 5-HT, dopamine and noradrenalin activity in the brain. The increase in 5-HT, which, in addition to dopamine, is a core mechanism of action for drug addiction, hyperactivates 5-HT(1A)-Rs. Here, we first review the role of the various 5-HT(1A)-R populations in spontaneous behavior to provide a background to elucidate the contribution of the 5-HT(1A)-Rs to the organization of psychostimulant-induced addiction behavior. The progress achieved in this field shows the fundamental contribution of brain 5-HT(1A)-Rs to virtually all behaviors associated with psychostimulant addiction. Importantly, the contribution of pre- and postsynaptic 5-HT(1A)-Rs can be dissociated and frequently act in opposite directions. We conclude that 5-HT(1A)-autoreceptors mainly facilitate psychostimulant addiction-related behaviors by a limitation of the 5-HT response in terminal areas. Postsynaptic 5-HT(1A)-Rs, in contrast, predominantly inhibit the expression of various addiction-related behaviors directly. In addition, they may also influence the local 5-HT response by feedback mechanisms. The reviewed findings do not only show a crucial role of 5-HT(1A)-Rs in the control of brain 5-HT activity and spontaneous behavior, but also their complex role in the regulation of the psychostimulant-induced 5-HT response and subsequent addiction-related behaviors.
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Affiliation(s)
- Christian P Müller
- Institute of Physiological Psychology I, University of Düsseldorf, Universitätsstr. 1, 40225 Düsseldorf, Germany.
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29
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Gillard ER, Coburn CG, de Leon A, Snissarenko EP, Bauce LG, Pittman QJ, Hou B, Currás-Collazo MC. Vasopressin autoreceptors and nitric oxide-dependent glutamate release are required for somatodendritic vasopressin release from rat magnocellular neuroendocrine cells responding to osmotic stimuli. Endocrinology 2007; 148:479-89. [PMID: 17082256 DOI: 10.1210/en.2006-0995] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Magnocellular neuroendocrine cells of the supraoptic nucleus (SON) release vasopressin (VP) systemically and locally during osmotic challenge. Although both central VP and nitric oxide (NO) release appear to reduce osmotically stimulated systemic VP release, it is unknown whether they interact locally in the SON to enhance somatodendritic release of VP, a phenomenon believed to regulate systemic VP release. In this study, we examined the contribution of VP receptor subtypes and NO to local VP release from the rat SON elicited by systemic injection of 3.5 m saline. Treatment of SON punches with VP receptor antagonists decreased osmotically stimulated intranuclear VP release. Similarly, blockade of NO production, or addition of NO scavengers, reduced stimulated VP, glutamate, and aspartate release, suggesting that local NO production and activity are critical for osmotically induced intranuclear VP and excitatory amino acid release. An increase in endogenous NO release from SON punches in response to hyperosmolality was confirmed by enzymatic NO assay. Consistent with enhanced glutamate and VP release from stimulated rat SON punches, the ionotropic glutamate receptor blocker kynurenate decreased stimulated local VP release without affecting NO release. These data suggest that NO enhances local VP release in part by facilitating local release of glutamate/aspartate and that glutamate receptor activity is required for the stimulation of local VP release by osmotic challenge. Collectively, these results suggest that local VP receptors, NO, and glutamatergic signaling mediate the amplification of intranuclear VP release during hyperosmolality and may contribute to efficient, but not exhaustive, systemic release of VP during osmoregulatory challenge.
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Affiliation(s)
- E R Gillard
- Department of Cell Biology and Neuroscience, 2110 Biological Sciences Building, University of California at Riverside, Riverside, California 92521, USA.
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30
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Ke JB, Zhong YM. Expression of somatostatin receptor subtype 5 in rat retinal amacrine cells. Neuroscience 2007; 144:1025-32. [PMID: 17156933 DOI: 10.1016/j.neuroscience.2006.10.047] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2006] [Revised: 10/27/2006] [Accepted: 10/27/2006] [Indexed: 01/01/2023]
Abstract
Somatostatin (SRIF), as a neuroactive peptide in the CNS, exerts its actions via five subtypes of specific receptors (ssts). In this work, the localization of sst(5) was studied immunocytochemically in rat retinal amacrine cells (ACs). Labeling for sst(5) was diffusely distributed throughout the full thickness of the inner plexiform layer (IPL) and formed two distinct fluorescence bands in the distal part of the IPL. Double labeling experiments showed that sst(5) was expressed in GABAergic ACs. It was further shown that labeling for sst(5) was observed in both dopaminergic and cholinergic ACs, stained by tyrosine hydroxylase (TH) and choline acetyltransferase (ChAT), respectively. The immunostaining appeared mainly on the cell membranes and somatodendritic compartments of these ACs. For the cholinergic ACs, weak sst(5)-immunoreactivity was also observed in the processes terminating in the IPL. In contrast, no sst(5)-immunoreactivity was found in glycinergic AII ACs, stained by parvalbumin (PV). Furthermore, labeling for SRIF was co-localized with sst(5) in both dopaminergic and cholinergic ACs. These results suggest that sst(5) may serve as an autoreceptor or conventional receptor in retinal ACs.
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Affiliation(s)
- J-B Ke
- Institute of Neurobiology and Institutes of Brain Science, Fudan University, 138 Yixueyuan Road, Shanghai 200032, PR China
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31
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Dabrowska J, Nowak P, Brus R. Desensitization of 5-HT(1A) autoreceptors induced by neonatal DSP-4 treatment. Eur Neuropsychopharmacol 2007; 17:129-37. [PMID: 16679005 DOI: 10.1016/j.euroneuro.2006.03.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/24/2005] [Revised: 02/07/2006] [Accepted: 03/21/2006] [Indexed: 11/19/2022]
Abstract
To examine the effect of noradrenergic lesion on the reactivity of central 5-HT(1A) receptors, DSP-4 (50 mg/kg) was administered neonatally 30 min after zimelidine (10 mg/kg) administration. 5-HT(1A) autoreceptors are involved in the regulation of serotonin (5-HT) synthesis. In HPLC assay R-(+)-8-OH-DPAT (0.03 mg/kg) significantly decreased 5-HT synthesis rate in striatum, hypothalamus and frontal cortex of control, whilst nonsignificantly in DSP-4-lesioned adult rats (10-12 weeks old). To determine which type of receptor, pre- or postsynaptically located, is involved in the attenuated response to 5-HT(1A) receptors' agonist, behavioral tests were conducted. R-(+)-8-OH-DPAT (0.015 mg/kg) caused hyperphagia of control rats, but did not change feeding of DSP-4 treated rats. R-(+)-8-OH-DPAT (0.1 mg/kg) induced hypothermia and "5-HT(1A) syndrome" in both control and DSP-4-lesioned animals. The nature of this phenomenon is attributable to the presynaptic adaptive mechanism and suggests the desensitization of 5-HT(1A) autoreceptors of rats with neonatal lesion of the central noradrenergic system.
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Affiliation(s)
- Joanna Dabrowska
- Department of Pharmacology, Medical University of Silesia, 38 Jordana St., 41-808 Zabrze, Poland.
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32
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Thompson SE, Ayman G, Woodhall GL, Jones RS. Depression of glutamate and GABA release by presynaptic GABAB receptors in the entorhinal cortex in normal and chronically epileptic rats. Neurosignals 2007; 15:202-15. [PMID: 17215590 PMCID: PMC2504722 DOI: 10.1159/000098515] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2006] [Accepted: 11/15/2006] [Indexed: 12/14/2022] Open
Abstract
Presynaptic GABA(B) receptors (GABA(B)R) control glutamate and GABA release at many synapses in the nervous system. In the present study we used whole-cell patch-clamp recordings of spontaneous excitatory and inhibitory synaptic currents in the presence of TTX to monitor glutamate and GABA release from synapses in layer II and V of the rat entorhinal cortex (EC)in vitro. In both layers the release of both transmitters was reduced by application of GABA(B)R agonists. Quantitatively, the depression of GABA release in layer II and layer V, and of glutamate release in layer V was similar, but glutamate release in layer II was depressed to a greater extent. The data suggest that the same GABA(B)R may be present on both GABA and glutamate terminals in the EC, but that the heteroreceptor may show a greater level of expression in layer II. Studies with GABA(B)R antagonists suggested that neither the auto- nor the heteroreceptor was consistently tonically activated by ambient GABA in the presence of TTX. Studies in EC slices from rats made chronically epileptic using a pilocarpine model of temporal lobe epilepsy revealed a reduced effectiveness of both auto- and heteroreceptor function in both layers. This could suggest that enhanced glutamate and GABA release in the EC may be associated with the development of the epileptic condition.
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Affiliation(s)
- Sarah E. Thompson
- Department of Pharmacy and Pharmacology, University of Bath, Bath, BA2 7AY, UK
| | - Göher Ayman
- Department of Pharmacy and Pharmacology, University of Bath, Bath, BA2 7AY, UK
| | - Gavin L. Woodhall
- The Molecular Biosciences Research Group, School of Life and Health Sciences, Aston University, Birmingham B4 7ET, UK
| | - Roland S.G. Jones
- Department of Pharmacy and Pharmacology, University of Bath, Bath, BA2 7AY, UK
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33
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Ma J, Lowe G. Calcium permeable AMPA receptors and autoreceptors in external tufted cells of rat olfactory bulb. Neuroscience 2006; 144:1094-108. [PMID: 17156930 PMCID: PMC2094052 DOI: 10.1016/j.neuroscience.2006.10.041] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2006] [Revised: 10/26/2006] [Accepted: 10/28/2006] [Indexed: 11/27/2022]
Abstract
Glomeruli are functional units of the olfactory bulb responsible for early processing of odor information encoded by single olfactory receptor genes. Glomerular neural circuitry includes numerous external tufted (ET) cells whose rhythmic burst firing may mediate synchronization of bulbar activity with the inhalation cycle. Bursting is entrained by glutamatergic input from olfactory nerve terminals, so specific properties of ionotropic glutamate receptors on ET cells are likely to be important determinants of olfactory processing. Particularly intriguing is recent evidence that AMPA receptors of juxta-glomerular neurons may permeate calcium. This could provide a novel pathway for regulating ET cell signaling. We tested the hypothesis that ET cells express functional calcium-permeable AMPA receptors. In rat olfactory bulb slices, excitatory postsynaptic currents (EPSCs) in ET cells were evoked by olfactory nerve shock, and by uncaging glutamate. We found attenuation of AMPA/kainate EPSCs by 1-naphthyl acetyl-spermine (NAS), an open-channel blocker specific for calcium permeable AMPA receptors. Cyclothiazide strongly potentiated EPSCs, indicating a major contribution from AMPA receptors. The current-voltage (I-V) relation of uncaging EPSCs showed weak inward rectification which was lost after > approximately 10 min of whole-cell dialysis, and was absent in NAS. In kainate-stimulated slices, Co(2+) ions permeated cells of the glomerular layer. Large AMPA EPSCs were accompanied by fluorescence signals in fluo-4 loaded cells, suggesting calcium permeation. Depolarizing pulses evoked slow tail currents with pharmacology consistent with involvement of calcium permeable AMPA autoreceptors. Tail currents were abolished by Cd(2+) and (+/-)-4-(4-aminophenyl)-2,3-dioxo-6-nitro-1,2,3,4-tetrahydrobenzo[f]quinoxaline-7-sulfonamide (NBQX), and were sensitive to NAS block. Glutamate autoreceptors were confirmed by uncaging intracellular calcium to evoke a large inward current. Our results provide evidence that calcium permeable AMPA receptors reside on ET cells, and are divided into at least two functionally distinct pools: postsynaptic receptors at olfactory nerve synaptic terminals, and autoreceptors sensitive to glutamate released from dendrodendritic synapses.
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Affiliation(s)
- J Ma
- Monell Chemical Senses Center, 3500 Market Street, Philadelphia, PA 19104-3308, USA
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Lévesque M, Wallman MJ, Parent R, Sík A, Parent A. Neurokinin-1 and neurokinin-3 receptors in primate substantia nigra. Neurosci Res 2006; 57:362-71. [PMID: 17134780 DOI: 10.1016/j.neures.2006.11.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2006] [Revised: 10/24/2006] [Accepted: 11/06/2006] [Indexed: 11/15/2022]
Abstract
Striatonigral axons co-release GABA and substance P (SP) at their target sites, but little is known about the action of SP at nigral level. Therefore, we studied immunohistochemically the cellular and subcellular localization of SP and its high affinity receptors neurokinin-1 (NK-1R) and neurokinin-3 (NK-3R) at nigral level in squirrel monkeys. Immunofluorescent studies revealed that, although SP+ fibers arborised more densely in the pars reticulata (SNr) than in the pars compacta (SNc), the two nigral divisions harbored numerous neurons expressing NK-1R and NK-3R. Confocal microscopic analyses showed that numerous SNr neurons and virtually all SNc dopaminergic neurons contained both NK-1R and NK-3R. At the electron microscope level, NK-1R and NK-3R were mainly associated with intracellular sites or located at extrasynaptic position on plasma membrane. A small proportion of SP+ boutons also showed NK-3R immunoreactivity. The distribution of NK-1R and NK-3R in SNr and SNc suggests that SP exerts its effect through postsynaptic receptors, as well as via presynaptic autoreceptors and heteroreceptors. These findings indicate that the excitatory peptide SP can modulate the inhibitory action of GABA at nigral level and suggest that the co-release of these two neuroactive substances should be taken into account when considering the functional organization of the basal ganglia.
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Affiliation(s)
- Martin Lévesque
- Centre de recherche Université Laval Robert-Giffard 2601, Chemin de la Canardière, Local F-6500 Beauport, Québec, Canada
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Talaia C, Queiroz G, Pinheiro H, Moura D, Gonçalves J. Involvement of G-protein βγ subunits on the influence of inhibitory α2-autoreceptors on the angiotensin AT1-receptor modulation of noradrenaline release in the rat vas deferens. Neurochem Int 2006; 49:698-707. [PMID: 16962210 DOI: 10.1016/j.neuint.2006.07.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2006] [Revised: 06/12/2006] [Accepted: 07/07/2006] [Indexed: 02/05/2023]
Abstract
The influence of alpha2-autoreceptors on the facilitation of [3H]-noradrenaline release mediated by angiotensin II was studied in prostatic portions of rat vas deferens preincubated with [3H]-noradrenaline. Angiotensin II enhanced tritium overflow evoked by trains of 100 pulses at 8 Hz, an effect that was attenuated by the AT1-receptor antagonist losartan (0.3-1 microM), at concentrations suggesting the involvement of the AT1B subtype. The effect of angiotensin II was also attenuated by inhibition of phospholipase C (PLC) and protein kinase C (PKC) indicating that prejunctional AT1-receptors are coupled to the PLC-PKC pathway. Angiotensin II (0.3-100 nM) enhanced tritium overflow more markedly, up to 64%, under conditions that favor alpha2-autoinhibition, observed when stimulation consisted of 100 pulses at 8 Hz, than under poor alpha2-autoinhibition conditions, only up to 14%, observed when alpha2-adrenoceptors were blocked with yohimbine (1 microM) or when stimulation consisted of 20 pulses at 50 Hz. Activation of PKC with 12-myristate 13-acetate (PMA, 0.1-3 microM) also enhanced tritium overflow more markedly under strong alpha2-autoinhibition conditions. Inhibition of Gi/o-proteins with pertussis toxin (8 microg/ml) or blockade of Gbetagamma subunits with the anti-betagamma peptide MPS-Phos (30 microM) attenuated the effects of angiotensin II and PMA. The results indicate that activation of AT1-receptors coupled to the PLC-PKC pathway enhances noradrenaline release, an effect that is markedly favoured by an ongoing activation of alpha2-autoreceptors. Interaction between alpha2-adrenoceptors and AT1-receptors seems to involve the betagamma subunits released from the Gi/o-proteins coupled to alpha2-adrenoceptors and protein kinase C activated by AT1-receptors.
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MESH Headings
- Adrenergic alpha-Antagonists/pharmacology
- Angiotensin II/metabolism
- Angiotensin II/pharmacology
- Animals
- Autoreceptors/drug effects
- Autoreceptors/metabolism
- Electric Stimulation
- Enzyme Inhibitors/pharmacology
- GTP-Binding Protein beta Subunits/antagonists & inhibitors
- GTP-Binding Protein beta Subunits/metabolism
- GTP-Binding Protein gamma Subunits/antagonists & inhibitors
- GTP-Binding Protein gamma Subunits/metabolism
- Male
- Neural Inhibition/drug effects
- Neural Inhibition/physiology
- Norepinephrine/metabolism
- Pertussis Toxin/pharmacology
- Presynaptic Terminals/drug effects
- Presynaptic Terminals/metabolism
- Protein Kinase C/antagonists & inhibitors
- Protein Kinase C/metabolism
- Rats
- Rats, Wistar
- Receptor Cross-Talk/drug effects
- Receptor Cross-Talk/physiology
- Receptor, Angiotensin, Type 1/drug effects
- Receptor, Angiotensin, Type 1/metabolism
- Receptors, Adrenergic, alpha-2/drug effects
- Receptors, Adrenergic, alpha-2/metabolism
- Signal Transduction/drug effects
- Signal Transduction/physiology
- Sympathetic Fibers, Postganglionic/drug effects
- Sympathetic Fibers, Postganglionic/metabolism
- Synaptic Transmission/drug effects
- Synaptic Transmission/physiology
- Tritium
- Type C Phospholipases/antagonists & inhibitors
- Type C Phospholipases/metabolism
- Vas Deferens/drug effects
- Vas Deferens/innervation
- Vas Deferens/metabolism
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Affiliation(s)
- Carlos Talaia
- Laboratory of Pharmacology, CEQOFFUP, Faculty of Pharmacy, University of Porto, Rua Aníbal Cunha, 164, 4050-047 Porto, Portugal
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Abstract
Activation of D2 autoreceptors on midbrain dopamine neurons has been shown previously to acutely open K+ channels to inhibit intrinsically generated pacemaker activity. Here we report that D2 autoreceptors act chronically to produce an opposite action: to increase the speed and regularity of repetitive action potential firing. Voltage-, current-, and dynamic-clamp experiments, using conventional whole-cell and perforated patch-clamp recording, with cultured rat midbrain dopamine neurons show that a change in the number of functional A-type K+ channels alters firing rate and susceptibility to irregularity produced by other channels. cAMP and protein kinase A mediate the long-term action of D2 receptors in a manner that counters the short-term effect of this signaling pathway on K+ channel gating. We conclude that D2 autoreceptors, in addition to mediating acute negative feedback, are responsible for long-term enhancement of the rate and fidelity of dopamine neuron pacemaker activity.
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Ding J, Guzman JN, Tkatch T, Chen S, Goldberg JA, Ebert PJ, Levitt P, Wilson CJ, Hamm HE, Surmeier DJ. RGS4-dependent attenuation of M4 autoreceptor function in striatal cholinergic interneurons following dopamine depletion. Nat Neurosci 2006; 9:832-42. [PMID: 16699510 DOI: 10.1038/nn1700] [Citation(s) in RCA: 199] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2006] [Accepted: 04/18/2006] [Indexed: 11/09/2022]
Abstract
Parkinson disease is a neurodegenerative disorder whose symptoms are caused by the loss of dopaminergic neurons innervating the striatum. As striatal dopamine levels fall, striatal acetylcholine release rises, exacerbating motor symptoms. This adaptation is commonly attributed to the loss of interneuronal regulation by inhibitory D(2) dopamine receptors. Our results point to a completely different, new mechanism. After striatal dopamine depletion, D(2) dopamine receptor modulation of calcium (Ca(2+)) channels controlling vesicular acetylcholine release in interneurons was unchanged, but M(4) muscarinic autoreceptor coupling to these same channels was markedly attenuated. This adaptation was attributable to the upregulation of RGS4-an autoreceptor-associated, GTPase-accelerating protein. This specific signaling adaptation extended to a broader loss of autoreceptor control of interneuron spiking. These observations suggest that RGS4-dependent attenuation of interneuronal autoreceptor signaling is a major factor in the elevation of striatal acetylcholine release in Parkinson disease.
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Affiliation(s)
- Jun Ding
- Department of Physiology and Institute for Neuroscience, Feinberg School of Medicine, Northwestern University, 303 East Chicago Avenue, Chicago, Illinois 60611, USA
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Evrard A, Barden N, Hamon M, Adrien J. Glucocorticoid Receptor-Dependent Desensitization of 5-HT1A Autoreceptors by Sleep Deprivation: Studies in GR-i Transgenic Mice. Sleep 2006; 29:31-6. [PMID: 16453979 DOI: 10.1093/sleep/29.1.31] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
UNLABELLED Sleep deprivation for one night induces mood improvement in depressed patients, an action that probably involves the serotonergic (5-HT) system. In animals, sleep deprivation and pharmacologic treatment with antidepressants exert similar effects on 5-HT neurotransmission, notably functional desensitization of 5-HT1A autoreceptors located on 5-HT neurons in the dorsal raphe nucleus (DRN). However, in stressful conditions, corticosterone can also induce a desensitization of these autoreceptors. STUDY OBJECTIVES To investigate the mechanisms of this adaptation during sleep deprivation and the possible involvement of corticosterone, we studied the effects of an 18-hour sleep deprivation, by forced locomotion, on 5-HT1A receptor-mediated firing response of DRN 5-HT neurons in transgenic mice with impaired glucocorticoid-receptor expression (GR-i) and in wild-type animals. We also examined the effects of chronic treatment with the antidepressant drug fluoxetine in the same paradigm. MEASUREMENTS AND RESULTS In both wild-type and GR-i mice, the 18-hour sleep deprivation or fluoxetine treatment had no effect on the spontaneous firing of 5-HT neurons recorded under anesthesia. However, sleep deprivation decreased the potency of the 5-HT1A agonist 8-OH-DPAT to inhibit 5-HT neuronal firing in wild-type mice, whereas it had no effect in GR-i animals. Conversely, after chronic fluoxetine treatment, the induced reduction of this 5-HT1A autoreceptor-driven response was of larger amplitude in GR-i than in wild-type mice. CONCLUSIONS These data suggest that glucocorticoid-receptor activation by corticosterone participates in the antidepressant-like adaptive changes in 5-HT1A autoreceptors in sleep-deprived mice. On the other hand, GR-i animals exhibited enhanced 5-HT1A autoreceptor desensitization induced by fluoxetine, in line with data in other animal models of depression.
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Affiliation(s)
- Alexis Evrard
- UMR 677 INSERM-UPMC, Neuropsychopharmacologie, CHUPitié-Salpêtrière, Paris, France
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Rios M, Lambe EK, Liu R, Teillon S, Liu J, Akbarian S, Roffler-Tarlov S, Jaenisch R, Aghajanian GK. Severe deficits in 5-HT2A-mediated neurotransmission in BDNF conditional mutant mice. ACTA ACUST UNITED AC 2006; 66:408-20. [PMID: 16408297 DOI: 10.1002/neu.20233] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
BDNF is thought to provide critical trophic support for serotonin neurons. In order to determine postnatal effects of BDNF on the serotonin system, we examined a line of conditional mutant mice that have normal brain content of BDNF during prenatal development but later depletion of this neurotrophin in the postnatal period. These mice show a behavioral phenotype that suggests serotonin dysregulation. However, as shown here, the presynaptic serotonin system in the adult conditional mutant mice appeared surprisingly normal from histological, biochemical, and electrophysiological perspectives. By contrast, a dramatic and unexpected postsynaptic 5-HT2A deficit in the mutant mice was found. Electrophysiologically, serotonin neurons appeared near normal except, most notably, for an almost complete absence of expected 5-HT2A -mediated glutamate and GABA postsynaptic potentials normally displayed by these neurons. Further analysis showed that BDNF mutants had much reduced 5-HT2A receptor protein in dorsal raphe nucleus and a similar deficit in prefrontal cortex, a region that normally shows a high level of 5-HT2A receptor expression. Recordings in prefrontal slice showed a marked deficit in 5-HT2A -mediated excitatory postsynaptic currents, similar to that seen in the dorsal raphe. These findings suggest that postnatal levels of BDNF play a relatively limited role in maintaining presynaptic aspects of the serotonin system and a much greater role in maintaining postsynaptic 5-HT2A and possibly other receptors than previously suspected.
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Affiliation(s)
- Maribel Rios
- Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.
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Abstract
The 5-HT1A receptor is expressed presynaptically as the primary somatodendritic autoreceptor on serotonergic raphe neurons, and postsynaptically in several brain regions. Signaling of the 5-HT1A autoreceptor was studied in RN46A cells, a model of serotonergic raphe neurons that express endogenous 5-HT1A receptors. In undifferentiated RN46A cells stably transfected with the wild-type 5-HT1A receptor, 5-HT1A receptor activation inhibited forskolin-induced cyclic adenosine monophosphate (cAMP) formation (by 50%), increased [Ca2+]i, and induced a novel inhibition (up to 60%) of phospho-p42/p44-mitogen-activated protein kinase (MAPK). Upon differentiation of non-transfected or 5-HT1A-transfected RN46A cells, agonist-mediated inhibition of MAPK was enhanced. These actions were blocked by pretreatment with pertussis toxin indicating mediation via Gi/Go proteins and the calcium response was blocked by preactivation of protein kinase C (PKC). In cells overexpressing the G beta gamma scavenger carboxyl-terminal domain of G protein receptor kinase 2 (GRK-CT), 5-HT1A receptor activation inhibited cAMP formation, but coupling to calcium mobilization and inhibition of MAPK was abolished. The activity of 5-HT1A receptors containing mutations of PKC sites in the second (i2: T149A) or third intracellular loop (i3: T229A/S253G/T343A) was tested. At comparable levels of receptor expression, the signaling of the 5-HT1A i3 mutant was similar to the 5-HT1A wild-type receptor, while the i2 and quadruple (i2/i3) mutants failed to couple to G beta gamma-mediated increase in [Ca2+]i or inhibition of MAPK, but did couple to G alpha i-mediated inhibition of cAMP. Thus, the i2-domain of the 5-HT1A autoreceptor is crucial for coupling to G beta gamma subunits and their subsequent responses (e.g. calcium mobilization and inhibition of MAPK activity).
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Affiliation(s)
- Neena Kushwaha
- Ottawa Health Research Institute (Neurosciences) and Department of Cellular and Molecular Medicine, University of Ottawa, 451 Smyth Road, Ottawa, Ontario, Canada K1H 8M5
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Gobert A, Billiras R, Cistarelli L, Millan MJ. Quantification and pharmacological characterization of dialysate levels of noradrenaline in the striatum of freely-moving rats: release from adrenergic terminals and modulation by alpha2-autoreceptors. J Neurosci Methods 2005; 140:141-52. [PMID: 15589344 DOI: 10.1016/j.jneumeth.2004.04.040] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2003] [Accepted: 04/28/2004] [Indexed: 10/26/2022]
Abstract
Information concerning striatal levels of noradrenaline (NA) remains inconsistent. Here we have addressed this issue using a sensitive method of HPLC coupled to amperometric detection. The NA reuptake-inhibitor, reboxetine, selectively elevated levels of NA versus dopamine (DA), and NA levels were also selectively elevated by the alpha2-adrenoceptor (AR) antagonist, atipamezole. The actions of atipamezole were mimicked by the preferential alpha2A-AR antagonist, BRL44408, while JO-1 and prazosin, preferential antagonists at alpha2C-ARs, caused less marked elevations in NA levels. In contrast to antagonists, the alpha2-AR agonist, S18616, decreased NA levels and likewise suppressed those of DA. Unilateral lesions of the substantia nigra with 6-hydroxydopamine depleted DA levels without affecting those of NA. Further, the D3/D2 receptor agonist, quinelorane, decreased levels of DA without modifying those of NA. However, the D3/D2 receptor antagonists, haloperidol and raclopride, and the DA reuptake-inhibitor, GBR12935, elevated levels of both DA and NA. Levels of 5-HT (but not of NA or DA) were increased only by the 5-HT reuptake-inhibitor, citalopram. They were decreased by S18616 and prazosin, reflecting the inhibitory and excitatory influence of alpha2- and alpha1-ARs, respectively, upon serotonergic pathways. In conclusion, NA in the striatum is derived from adrenergic terminals. Its release is subject to tonic, inhibitory control by alpha2-ARs, possibly involving both alpha2A- and alpha2C-AR subtypes, though their respective contribution requires clarification. A role of dopaminergic terminals in the reuptake of NA likely explains the elevation in its levels elicited by DA reuptake-inhibitors and D3/D2 receptor antagonists.
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Affiliation(s)
- Alain Gobert
- Psychopharmacology Department, Institut de Recherches Servier, Centre de Recherches de Croissy, 125 chemin de Ronde, Croissy/Seine 78290, France.
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Jomphe C, Bourque MJ, Fortin GD, St-Gelais F, Okano H, Kobayashi K, Trudeau LE. Use of TH-EGFP transgenic mice as a source of identified dopaminergic neurons for physiological studies in postnatal cell culture. J Neurosci Methods 2005; 146:1-12. [PMID: 15935217 DOI: 10.1016/j.jneumeth.2005.01.014] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2004] [Revised: 09/10/2004] [Accepted: 10/14/2004] [Indexed: 11/25/2022]
Abstract
The physiological and pharmacological properties of dopaminergic neurons in the brain are of major interest. Although much has been learned from cell culture studies, the physiological properties of these neurons remain difficult to study in such models because they are usually in minority and are difficult to distinguish from other non-dopaminergic neurons. Here we have taken advantage of a recently engineered transgenic mouse model expressing enhanced green fluorescence protein (EGFP) under the control of the tyrosine hydroxylase promoter to establish a more effective dopaminergic neuron cell culture model. We first evaluated the specificity of the EGFP expression. Although ectopic expression of EGFP was found in cultures derived from postnatal day 0 pups, this decreased over time in culture such that after 2 weeks, approximately 70% of EGFP-expressing neurons were dopaminergic. We next sought to validate this dopaminergic neuron culture model. We evaluated whether EGFP-expressing dopaminergic neurons displayed some of the well-established properties of dopaminergic neurons. Autoreceptor stimulation inhibited the activity of dopaminergic neurons while neurotensin receptor activation produced the opposite effect. Confocal imaging of the synaptic vesicle optical tracer FM4-64 in EGFP-expressing dopaminergic neurons demonstrated the feasibility of high resolution monitoring of the activity of single terminals established by these neurons. Together, this work provides evidence that primary cultures of postnatal TH-EGFP mice currently represent an excellent model to study the properties of these cells in culture.
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Affiliation(s)
- C Jomphe
- Department of Pharmacology, Faculty of Medicine, Centre de Recherche en Sciences Neurologiques, Université de Montréal, P.O. Box 6128, Succursale Centre-Ville, Montréal, Que., Canada H3C 3J7
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Ahlgren C, Eriksson A, Tellefors P, Ross SB, Stenfors C, Malmberg A. In vitro characterization of AR-A000002, a novel 5-hydroxytryptamine(1B) autoreceptor antagonist. Eur J Pharmacol 2005; 499:67-75. [PMID: 15363952 DOI: 10.1016/j.ejphar.2004.07.067] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2004] [Revised: 06/28/2004] [Accepted: 07/08/2004] [Indexed: 10/26/2022]
Abstract
The in vitro pharmacological properties of AR-A000002 ((R)-N-[5-methyl-8-(4-methylpiperazin-1-yl)-1,2,3,4-tetrahydro-2-naphthyl]-4-morpholinobenzamide), a novel 5-hydroxytryptamine (5-HT)(1B) receptor antagonist, were studied. AR-A000002 bound with high affinity to guinea pig cortex and recombinant guinea pig 5-HT(1B) receptors (Ki=0.24 and 0.47 nM) and with 10-fold lower affinity to 5-HT(1D) receptors. The compound displayed weak or no affinity for 63 other binding sites tested. In [35S]GTPgammaS assays AR-A000002 showed 50% efficacy and inhibited 5-HT stimulation with 66% and a pA2 value of 8.9. In slices of guinea pig cortex, AR-A000002 enhanced the outflow of [3H]5-HT upon electrical stimulation. The compound blocked sumatriptan-evoked contraction of rabbit saphenous veins without inducing any contraction itself. Thus, in these two systems AR-A000002 behaved as a 5-HT(1B) receptor antagonist. It is concluded that AR-A000002 is a selective high affinity 5HT(1B) receptor ligand that shows partial agonist activity in recombinant systems. In native tissues AR-A000002 behaves as a 5-HT(1B) receptor antagonist.
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Affiliation(s)
- Charlotte Ahlgren
- Department of Molecular Pharmacology, Local Discovery Research Area CNS & Pain Control, Astrazeneca R&D Södertälje S-151 85, Sweden
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Carey RJ, DePalma G, Damianopoulos E, Shanahan A, Müller CP, Huston JP. Evidence that the 5-HT1A autoreceptor is an important pharmacological target for the modulation of cocaine behavioral stimulant effects. Brain Res 2005; 1034:162-71. [PMID: 15713268 DOI: 10.1016/j.brainres.2004.12.012] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/04/2004] [Indexed: 11/24/2022]
Abstract
The psychostimulant effects of cocaine critically depend on the serotonergic (5-HT) system, of which the 5-HT1A receptor is an essential component. We recently showed divergent contributions of various pre- and postsynaptic 5-HT1A receptor populations to the behavioral effects of cocaine. Here, we further investigate the role of 5-HT1A autoreceptors in the acute and chronic stimulant effects of cocaine using 5-HT1A receptor ligands in autoreceptor preferring doses. In experiment 1, four groups of rats (N = 10) received either saline or the 5-HT1A agonist, 8-OHDPAT (0.05 mg/kg) 20 min prior to a saline or cocaine (10 mg/kg) injection on 9 consecutive days. In experiment 2, six groups (N = 10) were given either saline, the 5-HT1A antagonist, WAY 100635 (0.05 mg/kg) or 8-OHDPAT (0.05 mg/kg) plus WAY 100635 (0.05 mg/kg) 20 min before a saline or cocaine (10.0 mg/kg) treatment on 9 consecutive days. Initially, both the 8-OHDPAT and WAY 100635 pretreatments completely blocked the locomotor stimulant effects of cocaine whereas the combined 8-OHDPAT plus WAY 100635 pretreatment had no effect. In saline treated groups, neither the WAY 100635 nor the 8-OHDPAT plus WAY 100635 pretreatment influenced spontaneous activity levels, whereas the 8-OHDPAT alone severely reduced spontaneous activity. These effects persisted over the course of the 9 test sessions. A different pattern of results was obtained for the cocaine treatment groups. With repeated treatments, the WAY 100635 treatment always blocked the locomotor activation effect of cocaine, whereas the effects of 8-OHDPAT were transformed from an inhibition to an enhancement of cocaine locomotor stimulation. The combined 8-OHDPAT plus WAY 100635 pretreatment did not affect the stimulant effect of cocaine. These findings demonstrate that low dose autoreceptor preferring treatments with a 5-HT1A agonist and antagonist can strongly modify the behavioral stimulant effects of cocaine and suggest that the 5-HT1A autoreceptor may be an important pharmacological target for the development of treatments for cocaine addiction.
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Affiliation(s)
- Robert J Carey
- Research and Development (151), VA Medical Center, 800 Irving Avenue, Syracuse, NY 13210, USA.
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Lifschytz T, Gur E, Lerer B, Newman ME. Effects of triiodothyronine and fluoxetine on 5-HT1A and 5-HT1B autoreceptor activity in rat brain: regional differences. J Neurosci Methods 2004; 140:133-9. [PMID: 15589343 DOI: 10.1016/j.jneumeth.2004.03.028] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2003] [Accepted: 03/18/2004] [Indexed: 11/16/2022]
Abstract
The thyroid hormone triiodothyronine (T3) augments and accelerates the effects of antidepressant drugs. Although the majority of studies showing this have used tricyclics, a few studies have shown similar effects with the selective serotonin re-uptake inhibitor (SSRI) fluoxetine. In this study we investigated the effects of fluoxetine (5 mg/kg), T3 (20 microg/kg) and the combination of these drugs, each administered daily for 7 days, on serotonergic function in the rat brain, using in vivo microdialysis. Fluoxetine alone induced a trend towards desensitization of 5-HT1A autoreceptors as shown by a reduction in the effect of 8-OH-DPAT to lower 5-HT levels in frontal cortex, and desensitized 5-HT1B autoreceptors in frontal cortex. The combination of fluoxetine and T3 induced desensitization of 5-HT1B autoreceptors in hypothalamus. Since there is evidence linking hypothalamic function and depression, we suggest that this effect may partly account for the therapeutic efficacy of the combination of an SSRI and T3.
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MESH Headings
- 8-Hydroxy-2-(di-n-propylamino)tetralin/pharmacology
- Animals
- Autoreceptors/drug effects
- Autoreceptors/metabolism
- Brain/drug effects
- Brain/metabolism
- Brain Chemistry/drug effects
- Brain Chemistry/physiology
- Depressive Disorder/drug therapy
- Depressive Disorder/metabolism
- Depressive Disorder/physiopathology
- Down-Regulation/drug effects
- Down-Regulation/physiology
- Drug Synergism
- Drug Therapy, Combination
- Fluoxetine/pharmacology
- Hypothalamus/drug effects
- Hypothalamus/metabolism
- Male
- Microdialysis/instrumentation
- Microdialysis/methods
- Neurochemistry/instrumentation
- Neurochemistry/methods
- Prefrontal Cortex/drug effects
- Prefrontal Cortex/metabolism
- Rats
- Rats, Wistar
- Receptor, Serotonin, 5-HT1A/drug effects
- Receptor, Serotonin, 5-HT1A/metabolism
- Receptor, Serotonin, 5-HT1B/drug effects
- Receptor, Serotonin, 5-HT1B/metabolism
- Serotonin/metabolism
- Selective Serotonin Reuptake Inhibitors/pharmacology
- Triiodothyronine/metabolism
- Triiodothyronine/pharmacology
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Affiliation(s)
- Tzuri Lifschytz
- Biological Psychiatry Laboratory, Department of Psychiatry, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
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46
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Garcia AS, Barrera G, Burke TF, Ma S, Hensler JG, Morilak DA. Autoreceptor-mediated inhibition of norepinephrine release in rat medial prefrontal cortex is maintained after chronic desipramine treatment. J Neurochem 2004; 91:683-93. [PMID: 15485498 DOI: 10.1111/j.1471-4159.2004.02748.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Alterations in noradrenergic neurotransmission are important in the mechanism of action of many antidepressant drugs, including selective norepinephrine (NA) reuptake inhibitors such as desipramine (DMI). It has been suggested that chronic NA reuptake blockade induces a desensitization of inhibitory alpha(2)-adrenergic autoreceptors. This hypothesis was tested in experiment 1 using in vivo microdialysis to examine the degree of alpha(2)-autoreceptor-mediated inhibition of NA release in rat medial prefrontal cortex exerted by endogenous NA following chronic treatment with vehicle or DMI. This was accomplished by measuring the elevation of extracellular NA levels induced by acute administration of the alpha(2)-receptor antagonist yohimbine. An 8-fold increase in basal NA levels was observed after 21 days of DMI treatment. Further, acute yohimbine administration induced a robust elevation in NA levels which was not attenuated, and in fact at lower doses was greater in DMI-treated rats compared with vehicle-treated controls. In experiment 2, we addressed directly the functional status of terminal alpha(2)-autoreceptors in frontal cortex in vitro, in the absence of potentially confounding competition from elevated levels of endogenous NA, after chronic reuptake blockade. We observed no difference in the degree to which the alpha(2)-receptor agonist clonidine inhibited potassium-evoked [(3)H]-NA release from cortical slices taken from DMI- or vehicle-treated rats. Together, these data suggest that endogenous activation of alpha(2)-autoreceptors persists in restraining NA neurotransmission in the face of tonically elevated basal NA levels following chronic reuptake blockade.
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Affiliation(s)
- April S Garcia
- Department of Pharmacology and Center for Biomedical Neuroscience, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78229-3900, USA
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47
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Gur E, Lifschytz T, Van De Kar LD, Lerer B, Newman ME. Effects of triiodothyronine on 5-HT(1A) and 5-HT(1B) autoreceptor activity, and postsynaptic 5-HT(1A) receptor activity, in rat hypothalamus: lack of interaction with imipramine. Psychoneuroendocrinology 2004; 29:1172-83. [PMID: 15219641 DOI: 10.1016/j.psyneuen.2004.01.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/17/2003] [Revised: 10/23/2003] [Accepted: 01/26/2004] [Indexed: 10/26/2022]
Abstract
Triiodothyronine (T3) is effective in both augmenting and accelerating the therapeutic response to antidepressant drugs, especially tricyclics, and there is evidence from both human and animal studies that it acts on serotonergic neurotransmission. In this work we examined the effects of T3 alone and together with imipramine on 5-HT levels in the hypothalamus and on 5-HT(1A) and 5-HT(1B) autoreceptor sensitivity, using in vivo microdialysis in the rat. The effects of T3 on postsynaptic 5-HT(1A) receptor activity in the hypothalamus were also determined using a neuroendocrine challenge procedure. T3 administered daily at 20 microg/kg s.c. for 2 weeks reduced the sensitivity of 5-HT(1A) autoreceptors which control 5-HT release, as measured by the effect of 8-OH-DPAT to decrease 5-HT in the hypothalamus, and also the sensitivity of hypothalamic 5-HT(1B) receptors as measured by the effect of the 5-HT(1B) receptor agonist CP 93129 to decrease 5-HT release. Imipramine at 10 mg/kg daily for 4 weeks by osmotic minipump reduced 5-HT(1A) autoreceptor activity, as measured by the effect of 8-OH-DPAT in the hypothalamus, but the combination of T3 and imipramine given for 2 weeks did not affect either 5-HT(1A) or 5-HT(1B) autoreceptor activity. T3 at 20 microg/kg s.c. given daily for 1 week also reduced the sensitivity of postsynaptic 5-HT(1A) receptors in the hypothalamus, as measured by injection of 8-OH-DPAT and determination of the plasma ACTH and corticosterone responses. Animals which received T3 for 7 days showed a dose-dependent reduction in plasma free T4 levels but no change in total T3 levels. We conclude that while T3 alone affects both presynaptic and postsynaptic components of the serotonergic system, these effects may not be responsible for the therapeutic acceleration action seen with a combination of a tricyclic drug and T3.
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MESH Headings
- 8-Hydroxy-2-(di-n-propylamino)tetralin/pharmacology
- Adrenocorticotropic Hormone/metabolism
- Analysis of Variance
- Animals
- Antidepressive Agents, Tricyclic/pharmacology
- Autoreceptors/drug effects
- Autoreceptors/metabolism
- Corticosterone/metabolism
- Drug Interactions
- Hypothalamus/drug effects
- Hypothalamus/metabolism
- Imipramine/pharmacology
- Male
- Microdialysis
- Microinjections
- Rats
- Rats, Inbred Strains
- Receptor, Serotonin, 5-HT1A/drug effects
- Receptor, Serotonin, 5-HT1A/metabolism
- Receptor, Serotonin, 5-HT1B/drug effects
- Receptor, Serotonin, 5-HT1B/metabolism
- Serotonin Receptor Agonists/pharmacology
- Synaptic Transmission/drug effects
- Triiodothyronine/administration & dosage
- Triiodothyronine/physiology
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Affiliation(s)
- Eitan Gur
- Biological Psychiatry Laboratory, Department of Psychiatry, Hadassah-Hebrew University Medical Center, P.O. Box 12000, 91120 Jerusalem, Israel
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48
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Carey RJ, DePalma G, Damianopoulos E, Hopkins A, Shanahan A, Müller CP, Huston JP. Dopaminergic and serotonergic autoreceptor stimulation effects are equivalent and additive in the suppression of spontaneous and cocaine induced locomotor activity. Brain Res 2004; 1019:134-43. [PMID: 15306247 DOI: 10.1016/j.brainres.2004.05.091] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/28/2004] [Indexed: 10/26/2022]
Abstract
We used the D(2) receptor agonist, apomorphine (APO) and the 5-HT(1A) receptor agonist, 8-OHDPAT (8OH) in a low dose range to stimulate autoreceptors and in this way assess the separate and combined effects of reduced DA and 5-HT activity upon spontaneous and cocaine induced locomotor behavior. Two separate experiments were conducted. In the first experiment, separate groups of rats (N=10) were tested with either saline, 8OH, APO or 8OH plus APO (0.01, 0.025, 0.05 mg/kg). At 0.05 mg/kg, 8OH and APO induced similar dose related decreases (up to approximately 50%) in locomotor activity. The combined 8OH plus APO treatment induced dose-related decreases in locomotion (approximately 90%). At the 0.05 mg/kg dose level, the drug treatments given separately blocked cocaine induced increases in activity and the 8OH and APO inhibitory effects were again additive. In the second experiment, separate groups (N=10) received saline, 0.05 mg/kg APO, 0.05 mg/kg 8OH or 0.05 mg/kg APO plus 0.05 mg/kg 8OH. As in the first experiment, the 8OH and APO given separately reduced locomotor activity by approximately 50% and when given together, locomotor activity was virtually eliminated (reduced 80-90%). When the combined APO/8OH group also received the 5-HT(1A) antagonist, WAY 100635 (0.05 mg/kg), the effect on activity was equivalent to 0.05 mg/kg APO alone. Ex vivo neurochemical measurement of dopamine (DA) and serotonin (5-HT) metabolism confirmed that the APO decreased DA turnover, 8OH decreased 5-HT turnover and the combined treatment reduced both the DA and 5-HT turnover. Thus, for both spontaneous and cocaine induced locomotor behavior, the low dose 8OH and APO treatments suppressed locomotor activity and these effects were additive. These findings indicate that DA and 5-HT systems contribute separately to motoric activation. These results suggest that it is important to consider both DA and 5-HT contributions to disorders of motoric impoverishment such as Parkinson's disease as well as to hyperkinetic states such as those induced by stimulant drugs.
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49
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Rabiner EA, Bhagwagar Z, Gunn RN, Cowen PJ, Grasby PM. Preferential 5-HT1A autoreceptor occupancy by pindolol is attenuated in depressed patients: effect of treatment or an endophenotype of depression? Neuropsychopharmacology 2004; 29:1688-98. [PMID: 15127080 DOI: 10.1038/sj.npp.1300472] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Using positron emission tomography and the selective 5-HT1A receptor radioligand [11C]WAY100635, we previously demonstrated a preferential occupancy of 5-HT1A autoreceptors, compared to postsynaptic receptors by pindolol in healthy volunteers. We have speculated that preferential occupancy may be clinically important for the purported actions of pindolol in accelerating the antidepressant effects of selective serotonin re-uptake inhibitors (SSRIs). In this study, we have examined the preferential occupancy by pindolol of 5-HT1A autoreceptors, following three different pindolol regimes (10 mg single dose, 2.5 mg t.i.d., and 5 mg t.i.d., in 15 depressed patients on SSRIs. In addition, seven healthy volunteers were examined following a single 10 mg dose of pindolol. We found a preferential occupancy of 22.6+/-7.7% following a single dose of 10 mg of pindolol, in the healthy volunteers, which was attenuated in depressed patients on the same dose of pindolol to 2.9+/-10.8% (Student's t=3.94, df=12, p=0.002). In addition, we found a significant negative correlation between the degree of preferential occupancy and the severity of depression as assessed by the Hamilton depression rating score (HAM-D), Spearman's rho=-0.728, N=14, p=0.003, in the depressed sample. A possible mechanism underlying preferential occupancy and the attenuation of this phenomenon in depressed patients on SSRIs may include changes in the proportion of high affinity 5-HT1A sites in the autoreceptor region of the midbrain raphe. Speculatively, the degree of preferential occupancy may serve as a surrogate marker for depression, or the pharmacological effects of antidepressants.
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Affiliation(s)
- Eugenii A Rabiner
- PET Psychiatry, Translational Medicine and Technologies, GlaxoSmithKline, Cambridge, UK.
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50
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Shalom G, Gur E, Van de Kar LD, Newman ME. Repeated administration of the 5-HT1B receptor antagonist SB-224289 blocks the desensitisation of 5-HT1B autoreceptors induced by fluoxetine in rat frontal cortex. Naunyn Schmiedebergs Arch Pharmacol 2004; 370:84-90. [PMID: 15309378 DOI: 10.1007/s00210-004-0958-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2004] [Accepted: 06/18/2004] [Indexed: 10/26/2022]
Abstract
Desensitisation of 5-HT(1A) and 5-HT(1B) autoreceptors is thought to be the mechanism underlying the therapeutic effects of fluoxetine and other selective serotonin re-uptake inhibitors (SSRIs) when these are administered chronically, while blockade of these autoreceptors occurring on administration of an SSRI together with an autoreceptor antagonist is responsible for the acute increase in 5-HT levels in vivo observed under these circumstances. The effects of repeated administration of SSRIs together with 5-HT(1B) receptor antagonists on 5-HT levels and autoreceptor activity have not been studied previously with an in vivo method. In this work we found, using in vivo microdialysis that the effect of fluoxetine (5 mg/kg i.p. daily for 7 days) to desensitise 5-HT(1B) autoreceptors in frontal cortex, as measured by the action of CP 93129 (10 microM) to reduce 5-HT levels, was prevented by concomitant administration of the 5-HT(1B) receptor antagonist SB 224289 (2.5 mg/kg s.c.). 5-HT(1B) receptor activity in hypothalamus and 5-HT(1A) autoreceptor activity, as determined by the effects of s.c. 8-OH-DPAT to reduce 5-HT levels, were not altered either by fluoxetine alone at this dose or by fluoxetine in the presence of SB 224289. We conclude that the effects obtained when 5-HT(1B) autoreceptor antagonists are administered acutely together with SSRIs may not be maintained after repeated administration.
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Affiliation(s)
- Galit Shalom
- Biological Psychiatry Laboratory, Department of Psychiatry, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
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