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Honan LE, Fraser-Spears R, Daws LC. Organic cation transporters in psychiatric and substance use disorders. Pharmacol Ther 2024; 253:108574. [PMID: 38072333 PMCID: PMC11052553 DOI: 10.1016/j.pharmthera.2023.108574] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Revised: 11/01/2023] [Accepted: 11/30/2023] [Indexed: 12/23/2023]
Abstract
Psychiatric and substance use disorders inflict major public health burdens worldwide. Their widespread burden is compounded by a dearth of effective treatments, underscoring a dire need to uncover novel therapeutic targets. In this review, we summarize the literature implicating organic cation transporters (OCTs), including three subtypes of OCTs (OCT1, OCT2, and OCT3) and the plasma membrane monoamine transporter (PMAT), in the neurobiology of psychiatric and substance use disorders with an emphasis on mood and anxiety disorders, alcohol use disorder, and psychostimulant use disorder. OCTs transport monoamines with a low affinity but high capacity, situating them to play a central role in regulating monoamine homeostasis. Preclinical evidence discussed here suggests that OCTs may serve as promising targets for treatment of psychiatric and substance use disorders and encourage future research into their therapeutic potential.
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Affiliation(s)
- Lauren E Honan
- The University of Texas Health Science Center at San Antonio, Department of Cellular & Integrative Physiology, USA
| | - Rheaclare Fraser-Spears
- University of the Incarnate Word, Feik School of Pharmacy, Department of Pharmaceutical Sciences, USA
| | - Lynette C Daws
- The University of Texas Health Science Center at San Antonio, Department of Cellular & Integrative Physiology, USA; The University of Texas Health Science Center at San Antonio, Department of Pharmacology, USA.
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2
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Clauss NJ, Mayer FP, Owens WA, Vitela M, Clarke KM, Bowman MA, Horton RE, Gründemann D, Schmid D, Holy M, Gould GG, Koek W, Sitte HH, Daws LC. Ethanol inhibits dopamine uptake via organic cation transporter 3: Implications for ethanol and cocaine co-abuse. Mol Psychiatry 2023; 28:2934-2945. [PMID: 37308680 PMCID: PMC10615754 DOI: 10.1038/s41380-023-02064-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Revised: 12/20/2022] [Accepted: 03/29/2023] [Indexed: 06/14/2023]
Abstract
Concurrent cocaine and alcohol use is among the most frequent drug combination, and among the most dangerous in terms of deleterious outcomes. Cocaine increases extracellular monoamines by blocking dopamine (DA), norepinephrine (NE) and serotonin (5-HT) transporters (DAT, NET and SERT, respectively). Likewise, ethanol also increases extracellular monoamines, however evidence suggests that ethanol does so independently of DAT, NET and SERT. Organic cation transporter 3 (OCT3) is an emergent key player in the regulation of monoamine signaling. Using a battery of in vitro, in vivo electrochemical, and behavioral approaches, as well as wild-type and constitutive OCT3 knockout mice, we show that ethanol's actions to inhibit monoamine uptake are dependent on OCT3. These findings provide a novel mechanistic basis whereby ethanol enhances the neurochemical and behavioral effects of cocaine and encourage further research into OCT3 as a target for therapeutic intervention in the treatment of ethanol and ethanol/cocaine use disorders.
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Affiliation(s)
- N J Clauss
- Department of Cellular and Integrative Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX, 78229, USA
| | - F P Mayer
- Center for Physiology and Pharmacology, Medical University of Vienna, 1090, Vienna, Austria
- Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, DK-2200, Denmark
| | - W A Owens
- Department of Cellular and Integrative Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX, 78229, USA
| | - M Vitela
- Department of Cellular and Integrative Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX, 78229, USA
| | - K M Clarke
- Department of Cellular and Integrative Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX, 78229, USA
| | - M A Bowman
- Department of Cellular and Integrative Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX, 78229, USA
| | - R E Horton
- Department of Cellular and Integrative Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX, 78229, USA
| | - D Gründemann
- Department of Pharmacology, Faculty of Medicine and University Hospital Cologne, University of Cologne, 50931, Cologne, Germany
| | - D Schmid
- Center for Physiology and Pharmacology, Medical University of Vienna, 1090, Vienna, Austria
| | - M Holy
- Center for Physiology and Pharmacology, Medical University of Vienna, 1090, Vienna, Austria
| | - G G Gould
- Department of Cellular and Integrative Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX, 78229, USA
| | - W Koek
- Department of Cell Systems and Anatomy, University of Texas Health Science Center at San Antonio, San Antonio, TX, 78229, USA
| | - H H Sitte
- Center for Physiology and Pharmacology, Medical University of Vienna, 1090, Vienna, Austria
- Center for Addiction Research and Science, Medical University Vienna, Waehringerstrasse 13 A, 1090, Vienna, Austria
| | - L C Daws
- Department of Cellular and Integrative Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX, 78229, USA.
- Department of Pharmacology, University of Texas Health Science Center at San Antonio, San Antonio, TX, 78229, USA.
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3
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Sung U, Binda F, Savchenko V, Owens WA, Daws LC. Ca 2+ dependent surface trafficking of norepinephrine transporters depends on threonine 30 and Ca 2+ calmodulin kinases. J Chem Neuroanat 2016; 83-84:19-35. [PMID: 28017803 DOI: 10.1016/j.jchemneu.2016.12.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Revised: 12/09/2016] [Accepted: 12/15/2016] [Indexed: 11/28/2022]
Abstract
The antidepressant-sensitive norepinephrine (NE) transporter (NET) inactivates NE released during central and peripheral neuronal activity by transport into presynaptic cells. Altered NE clearance due to dysfunction of NET has been associated with the development of mental illness and cardiovascular diseases. NET activity in vivo is influenced by stress, neuronal activity, hormones and drugs. We investigated the mechanisms of Ca2+ regulation of NET and found that Ca2+ influenced both Vmax and Km for NE transport into cortical synaptosomes. Changes in extracellular Ca2+ triggered rapid and bidirectional surface trafficking of NET expressed in cultured cells. Deletion of residues 28-47 in the NET NH2-terminus abolished the Ca2+ effect on surface trafficking. Mutagenesis studies identified Thr30 in this region as the essential residue for both Ca2+- dependent phosphorylation and trafficking of NET. Depolarization of excitable cells increased surface NET in a Thr30 dependent manner. A proteomic analysis, RNA interference, and pharmacological inhibition supported roles of CaMKI and CaMKII in Ca2+-modulated NE transport and NET trafficking. Depolarization of primary noradrenergic neurons in culture with elevated K+ increased NET surface expression in a process that required external Ca2+ and depended on CaMK activity. Hippocampal NE clearance in vivo was also stimulated by depolarization, and inhibitors of CaMK signaling prevented this stimulation. In summary, Ca2+ signaling influenced surface trafficking of NET through a CaMK-dependent mechanism requiring Thr30.
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Affiliation(s)
- Uhna Sung
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232-8548, United States.
| | - Francesca Binda
- Institute of Cellular and Integrative Neurosciences, CNRS, Strasbourg, France
| | - Valentina Savchenko
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232-8548, United States
| | - William A Owens
- Department of Cellular and Integrative Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229-3900, United States
| | - Lynette C Daws
- Department of Cellular and Integrative Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229-3900, United States.
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Shnitko TA, Kennerly LC, Spear LP, Robinson DL. Ethanol reduces evoked dopamine release and slows clearance in the rat medial prefrontal cortex. Alcohol Clin Exp Res 2015; 38:2969-77. [PMID: 25581652 DOI: 10.1111/acer.12587] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2014] [Accepted: 09/18/2014] [Indexed: 01/26/2023]
Abstract
BACKGROUND Ethanol (EtOH) intoxication affects cognitive performance, contributing to attentional deficits and poor decision making, which may occur via actions in the medial prefrontal cortex (mPFC). mPFC function is modulated by the catecholamines dopamine and norepinephrine. In this study, we examine the acute effects of EtOH on electrically evoked dopamine release and clearance in the mPFC of anesthetized rats naïve to alcohol or chronically exposed to alcohol during adolescence. METHODS Dopamine release and clearance was evoked by electrical stimulation of the ventral tegmental area (VTA) and measured in the mPFC of anesthetized rats with fast-scan cyclic voltammetry. In Experiments 1 and 2, effects of a high dose of EtOH (4 g/kg, intraperitoneally) on dopamine neurotransmission in the mPFC of EtOH-naïve rats and rats given EtOH exposure during adolescence were investigated. Effects of cumulative dosing of EtOH (0.5 to 4 g/kg) on the dopamine release and clearance were investigated in Experiment 3. Experiment 4 studied effects of EtOH locally applied to the VTA on the dopamine neurotransmission in the mPFC of EtOH-naïve rats. RESULTS A high dose of EtOH decreased evoked dopamine release within 10 minutes of administration in EtOH-naïve rats. When tested via cumulative dosing from 0.5 to 4 g/kg, both 2 and 4 g/kg EtOH inhibited evoked dopamine release in the mPFC of EtOH-naïve rats, while 4 g/kg EtOH also slowed dopamine clearance. A similar effect on electrically evoked dopamine release in the mPFC was observed after infusion of EtOH into the VTA. Interestingly, intermittent EtOH exposure during adolescence had no effect on observed changes in mPFC dopamine release and clearance induced by acute EtOH administration. CONCLUSIONS Taken together, these data describe EtOH-induced reductions in the dynamics of VTA-evoked mPFC dopamine release and clearance, with the VTA contributing to the attenuation of evoked mPFC dopamine release induced by EtOH.
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Affiliation(s)
- Tatiana A Shnitko
- Bowles Center for Alcohol Study , University of North Carolina, Chapel Hill, North Carolina
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Methner DNR, Mayfield RD. Ethanol alters endosomal recycling of human dopamine transporters. J Biol Chem 2010; 285:10310-7. [PMID: 20133946 DOI: 10.1074/jbc.m109.029561] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Dynamic membrane trafficking of the monoamine dopamine transporter (DAT) regulates dopaminergic signaling. Various intrinsic and pharmacological modulators can alter this trafficking. Previously we have shown ethanol potentiates in vitro DAT function and increases surface expression. However, the mechanism underlying these changes is unclear. In the present study, we found ethanol directly regulates DAT function by altering endosomal recycling of the transporter. We defined ethanol action on transporter regulation by [(3)H]DA uptake functional analysis combined with biochemical and immunological assays in stably expressing DAT HEK-293 cells. Short-term ethanol exposure potentiated DAT function in a concentration-, but not time-dependent manner. This potentiation was accompanied by a parallel increase in DAT surface expression. Ethanol had no effect on function or surface localization of the ethanol-insensitive mutant (G130T DAT), suggesting a trafficking-dependent mechanism in mediating the ethanol sensitivity of the transporter. The ethanol-induced increase in DAT surface expression occurred without altering the overall size of DAT endosomal recycling pools. We found ethanol increased the DAT membrane insertion rate while having no effect on internalization of the transporter. Ethanol had no effect on the surface expression or trafficking of the endogenously expressing transferrin receptor, suggesting ethanol does not have a nonspecific effect on endosomal recycling. These results define a novel trafficking mechanism by which ethanol regulates DAT function.
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Affiliation(s)
- D Nicole Riherd Methner
- Waggoner Center for Alcohol and Addiction Research, University of Texas, Austin, Texas 78712, USA
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Paredes DA, Cartford MC, Catlow BJ, Samec A, Avilas M, George A, Schlunck A, Small B, Bickford PC. Neurotransmitter release during delay eyeblink classical conditioning: role of norepinephrine in consolidation and effect of age. Neurobiol Learn Mem 2008; 92:267-82. [PMID: 18809505 DOI: 10.1016/j.nlm.2008.08.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2008] [Revised: 08/28/2008] [Accepted: 08/28/2008] [Indexed: 11/30/2022]
Abstract
Delay classical eyeblink conditioning (EBC) is an important model of associative, cerebellar-dependent learning. Norepinephrine (NE) plays a significant modulatory role in the acquisition of learning; however, other neurotransmitters are also involved. The goal was to determine whether NE, gamma-aminobutyric acid (GABA) and glutamate (GLU) release are observed in cerebellar cortex during EBC, and whether such release was selectively associated with training. Further studies examined the role of the beta-noradrenergic receptor in consolidation of the learned response by local infusion of propranolol at 5-120 min following training into the cerebellar cortex. In vivo microdialysis coupled to EBC was performed to examine neurotransmitter release. An increase in the extracellular level of NE was observed during EBC and was maximal on day 1 and diminished in amplitude with subsequent days of training. No changes in baseline NE release were observed in pseudoconditioning indicating that NE release is directly related to the associative learning process. The extracellular levels of GABA were also increased selectively during paired training however, the magnitude of GABA release increased over days of training. GLU release was observed to increase during both paired and unpaired training, suggesting that learning does not occur prior to the information arriving in the cerebellum. When propranolol was administered at either 5-, 60-, or 120-min post-training, there was an inhibition of conditioned responses, these data support the hypothesis that NE is important for consolidation of learning. In another set of experiments we demonstrate that the timing of release of NE, GABA and glutamate are significantly delayed in onset and lengthened in duration in the 22-month-old F344 rats. Over days of training the timing of release becomes closer to the timing of training and this is associated with increased learning of conditioned responses in the aged rats.
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Affiliation(s)
- D A Paredes
- Center of Excellence for Aging and Brain Repair, Department of Neurosurgery, University of South Florida, Tampa, FL 33612, USA
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Boyce-Rustay JM, Palachick B, Hefner K, Chen YC, Karlsson RM, Millstein RA, Harvey-White J, Holmes A. Desipramine potentiation of the acute depressant effects of ethanol: modulation by alpha2-adrenoreceptors and stress. Neuropharmacology 2008; 55:803-11. [PMID: 18625256 PMCID: PMC2632577 DOI: 10.1016/j.neuropharm.2008.06.032] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2007] [Revised: 05/15/2008] [Accepted: 06/18/2008] [Indexed: 12/15/2022]
Abstract
Ethanol exerts effects on the brain noradrenergic system, and these are thought to contribute to the sedative/hypnotic (depressant) effects of ethanol. Recent studies suggest that the norepinephrine transporter (NET) plays an important role in modulating ethanol's depressant effects. The aim of the present study was to further characterize this role. Transporter blockers with varying affinity for NET versus the serotonin transporter (desipramine>fluoxetine>citalopram) were tested for their ability to alter ethanol's depressant effects, and for comparison, hypothermic effects. Effects of desipramine on another depressant, pentobarbital, were examined. Desipramine potentiation of ethanol's depressant effects was assessed following depletion of brain norepinephrine via N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine hydrochloride (DSP-4) treatment, or depletion of brain 5-HT via para-chlorophenylalanine methyl ester hydrochloride (PCPA) treatment. The effects of co-administration of either the selective alpha2-adrenoreceptor agonist (dexmedetomidine) or the selective alpha2-adrenoreceptor antagonist (atipamezole) on desipramine's effect on ethanol's depressant effects were examined. Given the close link between stress, ethanol and norepinephrine, desipramine potentiation of ethanol's depressant effects was tested following repeated forced swim stress. Results showed that desipramine, but not SERT-selective doses of citalopram or fluoxetine, strongly potentiated the depressant (not hypothermic) effects of ethanol. These effects were mimicked by dexmedetomidine and blocked by atipamezole, but not by depletion of either norepinephrine or 5-HT. Desipramine potentiation of ethanol's depressant effects was abolished following repeated stress. Present findings further support a major role for NET and the alpha2-adrenoreceptor in modulating the depressant effects of ethanol, with possible implications for understanding the role of noradrenergic dysfunction in stress-related alcoholism.
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Affiliation(s)
- Janel M Boyce-Rustay
- Laboratory for Integrative Neuroscience, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Rockville, MD, USA.
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8
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Li G, Abdel-Rahman AA. Direct evidence for imidazoline (I1) receptor modulation of ethanol action on norepinephrine-containing neurons in the rostral ventrolateral medulla in conscious spontaneously hypertensive rats. Alcohol Clin Exp Res 2007; 31:684-93. [PMID: 17374048 DOI: 10.1111/j.1530-0277.2007.00353.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND Enhancement of the rostral ventrolateral medulla (RVLM) presympathetic (norepinephrine, NE) neuronal activity represents a neurochemical mechanism for the pressor effect of ethanol. In this study, we tested the hypothesis that ethanol action on RVLM presympathetic neurons is selectively influenced by the signaling of the local imidazoline (I1) receptor. To support a neuroanatomical and an I1-signaling selectivity of ethanol, and to circumvent the confounding effects of anesthesia, the dose-related neurochemical and blood pressure effects of ethanol were investigated in the presence of selective pharmacological interventions that cause reduction in the activity of RVLM or nucleus tractus solitarius (NTS) NE neurons via local activation of the I1 or the alpha2-adrenergic receptor in conscious spontaneously hypertensive rats. RESULTS Local activation of the I1 receptor by rilmenidine (40 nmol) or by the I1/alpha2 receptor mixed agonist clonidine (1 nmol), and local activation of the alpha2-adrenergic receptor (alpha2AR) by the pure alpha2AR agonist alpha-methylnorepinephrine (alpha-MNE, 10 nmol) caused reductions in RVLM NE, and blood pressure. Intra-RVLM ethanol (1, 5, or 10 microg), microinjected at the nadir of the neurochemical and hypotensive responses, elicited dose-dependent increments in RVLM NE and blood pressure in the presence of local I1--but not alpha2-receptor activation. Only intra-NTS alpha-MNE, but not rilmenidine or clonidine, elicited reductions in local NE and blood pressure; ethanol failed to elicit any neurochemical or blood pressure responses in the presence of local activation of the alpha2AR within the NTS. CONCLUSION The findings support the neuroanatomical selectivity of ethanol, and support the hypothesis that the neurochemical (RVLM NE), and the subsequent cardiovascular, effects of ethanol are selectively modulated by I1 receptor signaling in the RVLM.
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Affiliation(s)
- Guichu Li
- Department of Pharmacology and Toxicology, Brody School of Medicine at East Carolina University, Greenville, North Carolina 27858, USA
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9
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Daws LC, Montañez S, Munn JL, Owens WA, Baganz NL, Boyce-Rustay JM, Millstein RA, Wiedholz LM, Murphy DL, Holmes A. Ethanol inhibits clearance of brain serotonin by a serotonin transporter-independent mechanism. J Neurosci 2006; 26:6431-8. [PMID: 16775130 PMCID: PMC6674049 DOI: 10.1523/jneurosci.4050-05.2006] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Brain serotonin (5-HT) modulates the neural and behavioral effects of ethanol in a manner that remains poorly understood. Here we show that treatment with physiologically relevant (i.e., moderately intoxicating) doses of ethanol inhibits clearance of 5-HT from extracellular fluid in the mouse hippocampus. This finding demonstrates, in vivo, a key molecular mechanism by which ethanol modulates serotonergic neurotransmission. The 5-HT transporter (5-HTT) is the principle means of 5-HT reuptake in the brain and an obvious candidate mechanism for the effect of ethanol to inhibit 5-HT clearance. However, our second major finding was that genetic inactivation of the 5-HTT in a knock-out mouse not only failed to prevent ethanol-induced inhibition of 5-HT clearance, but actually potentiated this effect. Ethanol-induced inhibition of 5-HT clearance was also potentiated in nonmutant mice by cotreatment with a 5-HTT antagonist. Providing a link with potential behavioral manifestations of this neural phenotype, 5-HTT knock-out mice also exhibited exaggerated sensitivity to behavioral intoxication, as assayed by the sedative/hypnotic effects of ethanol. This clearly demonstrates that the 5-HTT is not necessary for the neural and behavioral effects of ethanol observed herein and that genetic or pharmacological inactivation of the 5-HTT unmasks involvement of other principle mechanisms. These data are intriguing given growing evidence implicating the 5-HTT in the pathophysiology and treatment of alcoholism and neuropsychiatric conditions frequently comorbid with alcoholism, such as depression. The present findings provide new insights into the actions of ethanol on brain function and behavior.
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Affiliation(s)
- Lynette C Daws
- Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78229-3900, USA.
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10
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Sharp BM, Yatsula M, Fu Y. Effects of Galantamine, a Nicotinic Allosteric Potentiating Ligand, on Nicotine-Induced Catecholamine Release in Hippocampus and Nucleus Accumbens of Rats. J Pharmacol Exp Ther 2004; 309:1116-23. [PMID: 14769831 DOI: 10.1124/jpet.103.063586] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Galantamine, a drug for treatment of Alzheimer's disease, is a novel cholinergic agent with a dual mode of action that inhibits acetylcholinesterase and allosterically modulates nicotinic cholinergic receptors (nAChRs). Nicotine stimulates catecholamine secretion, inducing hippocampal norepinephrine (NE) release, and improves memory consolidation. Thus, the effect of galantamine on nicotine-induced hippocampal NE secretion was investigated. This was compared with the effect of galantamine on nicotine-induced dopamine (DA) release within the nucleus accumbens of the same rat. Nicotine (0.025-0.09 mg/kg i.v.) dose dependently increased NE and DA levels in microdialysates from the hippocampus and nucleus accumbens, respectively, of freely moving rats. Pretreatment with galantamine (3.0 mg/kg s.c.) 3 h before nicotine either potentiated NE responses to doses of nicotine that were ineffective alone (0.025-0.045 mg/kg) or significantly enhanced (0.065 mg/kg) NE responses, whereas galantamine was ineffective when administered 2 or 4 h before nicotine. In contrast to its effects on NE, galantamine did not alter accumbal DA responses to any dose of nicotine. These selective effects of galantamine on nicotine-stimulated NE secretion may reflect differences in local neural circuits that use nAChRs to modulate hippocampal NE versus accumbal DA release.
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Affiliation(s)
- Burt M Sharp
- Department of Pharmacology, Health Science Center, University of Tennessee, 874 Union Ave., Memphis, TN 38163, USA.
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11
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Freund RK, Gerhardt GA, Marshall KE, Palmer MR. Differences in norepinephrine clearance in cerebellar slices from low-alcohol-sensitive and high-alcohol-sensitive rats. Alcohol 2003; 30:9-18. [PMID: 12878270 DOI: 10.1016/s0741-8329(03)00098-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
High-alcohol-sensitive (HAS) and low-alcohol-sensitive (LAS) rats were bred for sensitivity and insensitivity, respectively, to the sedative/hypnotic effects of ethanol. These rats also display differential sensitivity to the depressant effects of locally applied ethanol on cerebellar Purkinje neurons in vivo. We have found that LAS animals exhibit a greater influence of endogenous beta-adrenergic activity on neuronal responses to gamma-aminobutyric acid (GABA) and ethanol than do HAS animals. In the current study, we investigated the possibility that the regulation of synaptic norepinephrine levels by norepinephrine transporters could contribute to a differential beta-adrenergic influence on GABA and ethanol sensitivity between HAS and LAS rats. We locally applied norepinephrine from a glass micropipette into the various layers of cerebellar brain slices prepared from LAS and HAS rats, and recorded the levels of norepinephrine clearance by using Nafion-coated carbon-fiber microelectrodes. Norepinephrine clearance was significantly faster by approximately 64% in the Purkinje cell layer of HAS rats. No differences in norepinephrine clearance were found in the molecular or the granule layer between LAS and HAS rats. The catecholamine uptake inhibitor nomifensine reduced norepinephrine clearance in both rat lines. These findings support the hypothesis that regulation of synaptic norepinephrine levels by norepinephrine transporter activity in the Purkinje cell layer may contribute to the differential sensitivity of Purkinje neurons to ethanol and GABA in LAS and HAS rats.
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Affiliation(s)
- Ronald K Freund
- Department of Pharmacology, Box C-236, University of Colorado Health Sciences Center, 4200 East 9th Avenue, Denver, CO 80262, USA.
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12
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Cocaine and antidepressant-sensitive biogenic amine transporters exist in regulated complexes with protein phosphatase 2A. J Neurosci 2001. [PMID: 11027216 DOI: 10.1523/jneurosci.20-20-07571.2000] [Citation(s) in RCA: 150] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Presynaptic transporter proteins regulate the clearance of extracellular biogenic amines after release and are important targets for multiple psychoactive agents, including amphetamines, cocaine, and antidepressant drugs. Recent studies reveal that dopamine (DA), norepinephrine (NE), and serotonin (5-HT) transporters (DAT, NET, and SERT, respectively) are rapidly regulated by direct or receptor-mediated activation of cellular kinases, particularly protein kinase C (PKC). With SERTs, PKC activation results in activity-dependent transporter phosphorylation and sequestration. Protein phosphatase 1/2A (PP1/PP2A) inhibitors, such as okadaic acid (OA) and calyculin A, also promote SERT phosphorylation and functional downregulation. How kinase, phosphatase, and transporter activities are linked mechanistically is unclear. In the present study, we found that okadaic acid-sensitive phosphatase activity is enriched in SERT immunoprecipitates from human SERT stably transfected cells. Moreover, blots of these immunoprecipitates reveal the presence of PP2A catalytic subunit (PP2Ac), findings replicated using brain preparations. Whole-cell treatments with okadaic acid or calyculin A diminished SERT/PP2Ac associations. Phorbol esters, which trigger SERT phosphorylation, also diminish SERT/PP2Ac associations, effects that can be blocked by PKC antagonists as well as the SERT substrate 5-HT. Similar transporter/PP2Ac complexes were also observed in coimmunoprecipitation studies with NETs and DATs. Our findings provide evidence for the existence of regulated heteromeric assemblies involving biogenic amine transporters and PP2A and suggest that the dynamic stability of these complexes may govern transporter phosphorylation and sequestration.
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13
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Gerhardt GA, Ksir C, Pivik C, Dickinson SD, Sabeti J, Zahniser NR. Methodology for coupling local application of dopamine and other chemicals with rapid in vivo electrochemical recordings in freely-moving rats. J Neurosci Methods 1999; 87:67-76. [PMID: 10065995 DOI: 10.1016/s0165-0270(98)00158-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Methodology is presented for constructing and using an electrode/microcannulae assembly that allows in vivo electrochemical measurements coupled with local application of dopamine (DA) and other chemicals in the unanesthetized freely-moving rat. Rats were implanted with a voltammetric electrode constructed of a carbon fiber sealed in fused silica tubing attached to a pair of stainless steel guide cannulae, into which fused silica injection cannulae were inserted for local application of DA and other chemicals. Precise delivery of nanoliter volumes was accomplished using a syringe drive combined with a fluid swivel to deliver the solutions to the injection cannulae. A newly-designed miniature potentiostat connected to a commutator via a modular telephone jack assembly allowed for high-speed chronoamperometric electrochemical recordings in freely-moving rats. Initial experiments characterized the in vitro electrochemical recording characteristics of the voltammetric electrode. In vivo studies were also carried out to study clearance of locally-applied DA and of potassium-evoked endogenous DA in the striatum and nucleus accumbens of freely-moving rats. In addition, the effects of chloral hydrate anesthesia on DA clearance signals in the nucleus accumbens were investigated. Moreover, the stability and reproducibility of this recording technique for measuring exogenous DA clearance was verified over a period of 5 days. Finally, the concurrent effects of systemic cocaine injection on DA uptake in nucleus accumbens and locomotor activity were examined. These studies support the conclusion that the methodology described herein allows for rapid chronoamperometric electrochemical recordings in freely-moving rats with precise microapplications of DA and other chemicals combined with concurrent measures of animal behavior.
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Affiliation(s)
- G A Gerhardt
- Department of Pharmacology, University of Colorado Health Sciences Center, Denver 80262, USA
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