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Daniels S, El Mansari M, Hamoudeh R, Blier P. Ketamine promptly normalizes excess norepinephrine and enhances dopamine neuronal activity in Wistar Kyoto rats. Front Pharmacol 2023; 14:1276309. [PMID: 38026921 PMCID: PMC10644068 DOI: 10.3389/fphar.2023.1276309] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2023] [Accepted: 10/06/2023] [Indexed: 12/01/2023] Open
Abstract
Ketamine acts primarily by blocking the N-methyl-D-aspartate (NMDA) receptor at the phencyclidine site. The rapid antidepressant properties of ketamine were demonstrated in the clinic and several behavioral models of depression in rodents. We hypothesized that the normalization of abnormal activity of monoamine neurons in Wistar Kyoto (WKY) rats contributes to the rapid antidepressant effects of ketamine. A single administration of ketamine (10 mg/kg, i. p) or saline was administered to anesthetized WKY rats before in vivo electrophysiological recordings of dorsal raphe nucleus (DRN) serotonin (5-HT), locus coeruleus (LC) norepinephrine (NE) and ventral tegmental area (VTA) dopamine (DA) neuronal activity. Pyramidal neurons from the medial prefrontal cortex (mPFC) were also recorded before and after a ketamine injection. In the VTA, ketamine elicited a significant increase in the population activity of DA neurons. This enhancement was consistent with findings in other depression-like models in which such a decreased population activity was observed. In the LC, ketamine normalized increased NE neuron burst activity found in WKY rats. In the DRN, ketamine did not significantly reverse 5-HT neuronal activity in WKY rats, which is dampened compared to Wistar rats. Ketamine did not significantly alter the neuronal activity of mPFC pyramidal neurons. These findings demonstrate that ketamine normalized NE neuronal activity and enhanced DA neuronal activity in WKY rats, which may contribute to its rapid antidepressant effect.
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Affiliation(s)
| | - Mostafa El Mansari
- Institute of Mental Health Research, University of Ottawa, Ottawa, ON, Canada
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Mendiguren A, Aostri E, Alberdi E, Pérez-Samartín A, Pineda J. Functional characterization of cannabidiol effect on the serotonergic neurons of the dorsal raphe nucleus in rat brain slices. Front Pharmacol 2022; 13:956886. [PMID: 36147343 PMCID: PMC9485894 DOI: 10.3389/fphar.2022.956886] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Accepted: 07/18/2022] [Indexed: 11/13/2022] Open
Abstract
Cannabidiol (CBD), the main non-psychoactive cannabinoid found in the cannabis plant, elicits several pharmacological effects via the 5-HT1A receptor. The dorsal raphe nucleus (DRN) is the main serotonergic cluster in the brain that expresses the 5-HT1A receptor. To date, the effect of CBD on the neuronal activity of DRN 5-HT cells and its interaction with somatodendritic 5-HT1A autoreceptors have not been characterized. Our aim was to study the effect of CBD on the firing activity of DRN 5-HT cells and the 5-HT1A autoreceptor activation by electrophysiological and calcium imaging techniques in male Sprague–Dawley rat brain slices. Perfusion with CBD (30 μM, 10 min) did not significantly change the firing rate of DRN 5-HT cells or the inhibitory effect of 5-HT (50–100 μM, 1 min). However, in the presence of CBD (30 μM, 10 min), the inhibitory effects of 8-OH-DPAT (10 nM) and ipsapirone (100 nM) were reduced by 66% and 53%, respectively. CBD failed to reverse ipsapirone-induced inhibition, whereas perfusion with the 5-HT1A receptor antagonist WAY100635 (30 nM) completely restored by 97.05 ± 14.63% the firing activity of 5-HT cells. Administration of AM251 (1 µM), MDL100907 (30 nM), or picrotoxin (20 μM) did not change the blockade produced by CBD (30 μM) on ipsapirone-induced inhibition. Our study also shows that CBD failed to modify the KCl (15 mM, 4 min)-evoked increase in [Ca2+]i or the inhibitory effect of ipsapirone (1 μM, 4 min) on KCl-evoked [Ca2+]i. In conclusion, CBD does not activate 5-HT1A autoreceptors, but it hindered the inhibitory effect produced by selective 5-HT1A receptor agonists on the firing activity of DRN 5-HT cells through a mechanism that does not involve CB1, 5-HT2A, or GABAA receptors. Our data support a negative allosteric modulation of DRN somatodendritic 5-HT1A receptor by CBD.
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Affiliation(s)
- Aitziber Mendiguren
- Department of Pharmacology, Faculty of Medicine and Nursing, University of the Basque Country (UPV/EHU), Leioa, Spain
- *Correspondence: Aitziber Mendiguren,
| | - Erik Aostri
- Department of Pharmacology, Faculty of Medicine and Nursing, University of the Basque Country (UPV/EHU), Leioa, Spain
| | - Elena Alberdi
- Achucarro Basque Center for Neuroscience, Department of Neuroscience, Faculty of Medicine and Nursing, University of the Basque Country (UPV/EHU), Leioa, Spain
| | - Alberto Pérez-Samartín
- Achucarro Basque Center for Neuroscience, Department of Neuroscience, Faculty of Medicine and Nursing, University of the Basque Country (UPV/EHU), Leioa, Spain
| | - Joseba Pineda
- Department of Pharmacology, Faculty of Medicine and Nursing, University of the Basque Country (UPV/EHU), Leioa, Spain
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Movassaghi CS, Perrotta KA, Yang H, Iyer R, Cheng X, Dagher M, Fillol MA, Andrews AM. Simultaneous serotonin and dopamine monitoring across timescales by rapid pulse voltammetry with partial least squares regression. Anal Bioanal Chem 2021; 413:6747-6767. [PMID: 34686897 PMCID: PMC8551120 DOI: 10.1007/s00216-021-03665-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Revised: 09/11/2021] [Accepted: 09/14/2021] [Indexed: 11/12/2022]
Abstract
Many voltammetry methods have been developed to monitor brain extracellular dopamine levels. Fewer approaches have been successful in detecting serotonin in vivo. No voltammetric techniques are currently available to monitor both neurotransmitters simultaneously across timescales, even though they play integrated roles in modulating behavior. We provide proof-of-concept for rapid pulse voltammetry coupled with partial least squares regression (RPV-PLSR), an approach adapted from multi-electrode systems (i.e., electronic tongues) used to identify multiple components in complex environments. We exploited small differences in analyte redox profiles to select pulse steps for RPV waveforms. Using an intentionally designed pulse strategy combined with custom instrumentation and analysis software, we monitored basal and stimulated levels of dopamine and serotonin. In addition to faradaic currents, capacitive currents were important factors in analyte identification arguing against background subtraction. Compared to fast-scan cyclic voltammetry-principal components regression (FSCV-PCR), RPV-PLSR better differentiated and quantified basal and stimulated dopamine and serotonin associated with striatal recording electrode position, optical stimulation frequency, and serotonin reuptake inhibition. The RPV-PLSR approach can be generalized to other electrochemically active neurotransmitters and provides a feedback pipeline for future optimization of multi-analyte, fit-for-purpose waveforms and machine learning approaches to data analysis.
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Affiliation(s)
- Cameron S Movassaghi
- Department of Chemistry & Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095, USA
- California NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA, 90095, USA
| | - Katie A Perrotta
- Department of Chemistry & Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095, USA
| | - Hongyan Yang
- Department of Psychiatry and Biobehavioral Sciences, Semel Institute for Neuroscience and Human Behavior, and Hatos Center for Neuropharmacology, University of California, Los Angeles, Los Angeles, CA, 90095, USA
| | - Rahul Iyer
- Department of Electrical Engineering, University of California, Los Angeles, Los Angeles, CA, 90095, USA
| | - Xinyi Cheng
- Department of Chemistry & Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095, USA
| | - Merel Dagher
- Molecular Toxicology Interdepartmental Program, University of California, Los Angeles, Los Angeles, CA, 90095, USA
| | - Miguel Alcañiz Fillol
- Interuniversity Research Institute for Molecular Recognition and Technological Development, Universitat Politècnica de València - Universitat de València, Camino de Vera s/n, 46022, Valencia, Spain.
| | - Anne M Andrews
- Department of Chemistry & Biochemistry, University of California, Los Angeles, Los Angeles, CA, 90095, USA.
- California NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA, 90095, USA.
- Department of Psychiatry and Biobehavioral Sciences, Semel Institute for Neuroscience and Human Behavior, and Hatos Center for Neuropharmacology, University of California, Los Angeles, Los Angeles, CA, 90095, USA.
- Molecular Toxicology Interdepartmental Program, University of California, Los Angeles, Los Angeles, CA, 90095, USA.
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Iro CM, Hamati R, El Mansari M, Blier P. Repeated but Not Single Administration of Ketamine Prolongs Increases of the Firing Activity of Norepinephrine and Dopamine Neurons. Int J Neuropsychopharmacol 2021; 24:570-579. [PMID: 33674836 PMCID: PMC8299825 DOI: 10.1093/ijnp/pyab010] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Revised: 02/17/2021] [Accepted: 02/25/2021] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND Clinical studies have shown that the rapid antidepressant effect of the glutamate N-methyl-D-aspartate receptor antagonist ketamine generally disappears within 1 week but can be maintained by repeated administration. Preclinical studies showed that a single ketamine injection immediately increases the firing and burst activity of norepinephrine (NE) neurons, but not that of serotonin (5-HT) neurons. It also enhances the population activity of dopamine (DA) neurons. In the present study, we investigated whether such alterations of monoamine neuronal firing are still present 1 day after a single injection, and whether they can be maintained by repeated injections. METHODS Rats received a single ketamine injection or 6 over 2 weeks and the firing activity of dorsal raphe nucleus 5-HT, locus coeruleus NE, and ventral tegmental area DA neurons was assessed. RESULTS One day following a single injection of ketamine, there was no change in the firing activity of 5-HT, NE, or DA neurons. One day after repeated ketamine administration, however, there was a robust increase of the firing activity of NE neurons and an enhancement of burst and population activities of DA neurons, but still no change in firing parameters of 5-HT neurons. The increased activity of NE neurons was no longer present 3 days after the last injection, whereas that of DA neurons was still present. DA neurons were firing normally 7 days after repeated injections. CONCLUSION These results imply that the enhanced activity of NE and DA neurons may play a significant role in the maintenance of the antidepressant action of ketamine.
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Affiliation(s)
- Chidiebere M Iro
- Mood Disorders Research Unit, University of Ottawa Institute of Mental Health Research, Ottawa, Ontario, Canada
| | - Rami Hamati
- Mood Disorders Research Unit, University of Ottawa Institute of Mental Health Research, Ottawa, Ontario, Canada
| | - Mostafa El Mansari
- Mood Disorders Research Unit, University of Ottawa Institute of Mental Health Research, Ottawa, Ontario, Canada,Correspondence: Mostafa El Mansari, PhD, University of Ottawa Institute of Mental Health Research, Mood Disorders Research Unit, 1145 Carling Avenue, Ottawa, ON K1Z 7K4, Canada ()
| | - Pierre Blier
- Mood Disorders Research Unit, University of Ottawa Institute of Mental Health Research, Ottawa, Ontario, Canada
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El Mansari M, Ebrahimzadeh M, Hamati R, Iro CM, Farkas B, Kiss B, Adham N, Blier P. Long-term administration of cariprazine increases locus coeruleus noradrenergic neurons activity and serotonin 1A receptor neurotransmission in the hippocampus. J Psychopharmacol 2020; 34:1143-1154. [PMID: 32684081 DOI: 10.1177/0269881120936891] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
BACKGROUND Cariprazine, the novel dopamine (DA) D3-preferring D3/D2 and serotonin (5-HT)1A receptor partial agonist, has activity as an adjunctive therapy in major depressive disorder (MDD). AIMS This study aims to investigate the effects of chronic cariprazine administration in combination with the selective serotonin reuptake inhibitor escitalopram on the activity of monoaminergic systems. METHODS Rats received cariprazine alone and in adjunct to escitalopram for 2 and 14 days and the firing activity of dorsal raphe nucleus 5-HT, locus coeruleus norepinephrine (NE) and ventral tegmental area DA neurons was assessed. 5-HT and NE neurotransmission in hippocampus pyramidal neurons was evaluated by assessing tonic activation of their 5-HT1A, and α1- and α2-adrenergic receptors, using their selective antagonists. RESULTS Two and 14-day cariprazine regimens increased the firing rate of NE, but not 5-HT and DA neurons. Addition of cariprazine to escitalopram reversed the inhibitory effect of escitalopram on NE but not 5-HT and DA neurons. In the hippocampus, there was an increase in neurotransmission at 5-HT1A receptors in cariprazine-treated rats, but no change in overall NE transmission by either regimen. CONCLUSION Cariprazine increased NE neuronal firing and reversed the escitalopram-induced inhibition of these neurons. Despite a lack of effect on 5-HT neuronal firing activity, there was an increase in tonic activation of hippocampus 5-HT1A receptors by cariprazine alone but not with the combination. These effects provide a possible rationale for the clinical efficacy of cariprazine as an adjunctive strategy in patients with MDD.
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Affiliation(s)
- Mostafa El Mansari
- Mood Disorders Research Unit, University of Ottawa Institute of Mental Health Research, Ottawa, ON, Canada
| | - Mohammad Ebrahimzadeh
- Mood Disorders Research Unit, University of Ottawa Institute of Mental Health Research, Ottawa, ON, Canada
| | - Rami Hamati
- Mood Disorders Research Unit, University of Ottawa Institute of Mental Health Research, Ottawa, ON, Canada
| | - Chidibere M Iro
- Mood Disorders Research Unit, University of Ottawa Institute of Mental Health Research, Ottawa, ON, Canada
| | | | - Béla Kiss
- Gedeon Richter Plc, Budapest, Hungary
| | | | - Pierre Blier
- Mood Disorders Research Unit, University of Ottawa Institute of Mental Health Research, Ottawa, ON, Canada
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Di Miceli M, Omoloye A, Gronier B. Chronic methylphenidate treatment during adolescence has long-term effects on monoaminergic function. J Psychopharmacol 2019; 33:109-121. [PMID: 30334678 DOI: 10.1177/0269881118805494] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
BACKGROUND Psychostimulants like methylphenidate or D-amphetamine are often prescribed for attention deficit and hyperactivity disorders in children. Whether such drugs can be administered into a developing brain without consequences in adulthood is still an open question. METHODS Here, using in vivo extracellular electrophysiology in anesthetised preparations, combined with behavioural assays, we have examined the long-term consequences in adulthood of a chronic methylphenidate oral administration (5 mg/kg/day, 15 days) in early adolescent (post-natal day 28) and late adolescent (post-natal day 42) rats, by evaluating body weight change, sucrose preference (indicator of anhedonia), locomotor sensitivity to D-amphetamine and electrical activities of ventral tegmental area dopamine and dorsal raphe nucleus serotonin neurons. RESULTS Chronic methylphenidate treatment during early or late adolescence did not induce weight deficiencies and anhedonia-like behaviours at adulthood. However, it increased bursting activities of dorsal raphe nucleus serotonin neurons. Furthermore, chronic methylphenidate treatment during early but not during late adolescence enhanced D-amphetamine-induced rearing activity, as well as ventral tegmental area dopamine cell excitability (firing, burst and population activity), associated with a partial desensitisation of dopamine D2 auto-receptors. CONCLUSIONS We have demonstrated here that early, but not late, adolescent exposure to oral methylphenidate may induce long-lasting effects on monoamine neurotransmission. The possible clinical implication of these data will be discussed.
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Affiliation(s)
- Mathieu Di Miceli
- Pharmacology and Neuroscience Research Group, Leicester School of Pharmacy, De Montfort University, Leicester, UK
| | - Adesina Omoloye
- Pharmacology and Neuroscience Research Group, Leicester School of Pharmacy, De Montfort University, Leicester, UK
| | - Benjamin Gronier
- Pharmacology and Neuroscience Research Group, Leicester School of Pharmacy, De Montfort University, Leicester, UK
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Shikanai H, Izumi T. [In vivo analysis for mechanism of drug action by juxtacellular recording]. Nihon Yakurigaku Zasshi 2018; 152:28-32. [PMID: 29998949 DOI: 10.1254/fpj.152.28] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Electrophysiological methods are commonly used in neuroscience and pharmacology to reveal the mechanisms of drug action. In vivo analysis of the mechanisms of drug action is a particularly important method in neuropharmacology. Here, we show the juxtacellular recording method to characterize the electrophysiological and neurochemical properties of neurons. Using juxtacellular recording, researchers can record the membrane potential from single neurons, and examine action potential parameters, such as the width and coefficient variance of inter-spike intervals. Additionally, recorded neurons can be labeled using neurobiotin, and neurochemical properties can be revealed by a combination of immunohistochemical staining and in situ hybridization. We introduce an experiment testing the effects of a phosphodiesterase 4 (PDE4) inhibitor on the fronto-striatal circuit using juxtacellular recording. The cerebral cortex-nucleus accumbens (NAcc)-external segment of globus pallidus (GPe)-subthalamic nucleus (STN)-substantia nigra pars reticulata (SNr) pathway is the neurobiological basis of many neuropsychiatric disorders. Several components of this pathway are particularly important for the regulation of motor action and cognitive function: 1) STN-SNr pathway (hyperdirect pathway), 2) NAcc-SNr pathway (direct pathway), and 3) GPe-STN-SNr pathway (indirect pathway). Researchers can record tri-phasic responses reflecting these pathways using electro-stimulation in cerebral cortex. A PDE4 inhibitor, roflumilast, affected the 2) direct pathway as well as the 3) indirect pathway, but not the 1) hyperdirect pathway. The current findings suggest that PDE4 inhibition could be considered as a possible treatment for cognitive deficits related to fronto-striatal disorders such as attention deficit/hyperactivity disorder, and Parkinson's disease.
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Affiliation(s)
- Hiroki Shikanai
- Department of Pharmacology, Faculty of Pharmaceutical Sciences, Health Sciences University of Hokkaido
| | - Takeshi Izumi
- Department of Pharmacology, Faculty of Pharmaceutical Sciences, Health Sciences University of Hokkaido
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Wong-Lin K, Wang DH, Moustafa AA, Cohen JY, Nakamura K. Toward a multiscale modeling framework for understanding serotonergic function. J Psychopharmacol 2017; 31:1121-1136. [PMID: 28417684 PMCID: PMC5606304 DOI: 10.1177/0269881117699612] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Despite its importance in regulating emotion and mental wellbeing, the complex structure and function of the serotonergic system present formidable challenges toward understanding its mechanisms. In this paper, we review studies investigating the interactions between serotonergic and related brain systems and their behavior at multiple scales, with a focus on biologically-based computational modeling. We first discuss serotonergic intracellular signaling and neuronal excitability, followed by neuronal circuit and systems levels. At each level of organization, we will discuss the experimental work accompanied by related computational modeling work. We then suggest that a multiscale modeling approach that integrates the various levels of neurobiological organization could potentially transform the way we understand the complex functions associated with serotonin.
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Affiliation(s)
- KongFatt Wong-Lin
- Intelligent Systems Research Centre, School of Computing and Intelligent Systems, University of Ulster, Magee Campus, Derry~Londonderry, UK
| | - Da-Hui Wang
- School of Systems Science, and National Key Laboratory of Cognitive Neuroscience and Learning, Beijing Normal University, Beijing, China
| | - Ahmed A Moustafa
- School of Social Sciences and Psychology, and Marcs Institute for Brain and Behaviour, University of Western Sydney, Sydney, Australia
| | - Jeremiah Y Cohen
- Solomon H. Snyder Department of Neuroscience, Brain Science Institute, Johns Hopkins University School of Medicine, Baltimore, USA
| | - Kae Nakamura
- Department of Physiology, Kansai Medical University, Hirakata, Osaka, Japan
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El Mansari M, Manta S, Oosterhof C, El Iskandrani KS, Chenu F, Shim S, Blier P. Restoration of serotonin neuronal firing following long-term administration of bupropion but not paroxetine in olfactory bulbectomized rats. Int J Neuropsychopharmacol 2015; 18:pyu050. [PMID: 25522394 PMCID: PMC4360219 DOI: 10.1093/ijnp/pyu050] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
BACKGROUND Olfactory bulbectomized rats generally manifest many of the neurochemical, physiological, and behavioral features of major depressive disorder in humans. Another interesting feature of this model is that it responds to chronic but not acute antidepressant treatments, including selective serotonin reuptake inhibitors. The purpose of the present study was first to characterize the firing activity of dorsal raphe serotonin neurons in olfactory bulbectomized rats and then examine the effects of 2 antidepressants, bupropion and paroxetine. METHODS Olfactory bulbectomy was performed by aspirating olfactory bulbs in anesthetized rats. Vehicle and drugs were delivered for 2 and 14 days via subcutaneously implanted minipumps. In vivo electrophysiological recordings were carried out in male anesthetized Sprague-Dawley rats. RESULTS Following ablation of olfactory bulbs, the firing rate of serotonin neurons was decreased by 36%, leaving those of norepinephrine and dopamine neurons unchanged. In olfactory bulbectomized rats, bupropion (30 mg/kg/d) restored the firing rate of serotonin neurons to the control level following 2- and 14-day administration and also induced an increase in the tonic activation of serotonin(1A) receptors; paroxetine (10 mg/kg/d) did not result in a return to normal of the attenuated firing of serotonin neurons in olfactory bulbectomized rats. In the hippocampus, although at a higher dose of WAY 100635 than that required in bupropion-treated animals, paroxetine administration also resulted in an increase in the tonic activation of serotonin(1A) receptors. CONCLUSIONS The present results indicate that unlike paroxetine, bupropion administration normalized serotonin neuronal activity and increased tonic activation of the serotonin(1A) receptors in hippocampus.
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Affiliation(s)
- Mostafa El Mansari
- University of Ottawa Institute of Mental Health Research, Ottawa, ON, Canada.
| | - Stella Manta
- University of Ottawa Institute of Mental Health Research, Ottawa, ON, Canada
| | - Chris Oosterhof
- University of Ottawa Institute of Mental Health Research, Ottawa, ON, Canada
| | | | - Franck Chenu
- University of Ottawa Institute of Mental Health Research, Ottawa, ON, Canada
| | - Stacey Shim
- University of Ottawa Institute of Mental Health Research, Ottawa, ON, Canada
| | - Pierre Blier
- University of Ottawa Institute of Mental Health Research, Ottawa, ON, Canada
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Shim S, El Mansari M, Blier P. Modulation of the Antidepressant-Like Effects of Sustained Administration of Carisbamate and Lamotrigine on Monoaminergic Systems: Electrophysiological Studies in the Rat Brain. J Pharmacol Exp Ther 2013; 347:487-96. [DOI: 10.1124/jpet.113.203315] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
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Raphe serotonin neurons are not homogenous: electrophysiological, morphological and neurochemical evidence. Neuropharmacology 2011; 61:524-43. [PMID: 21530552 DOI: 10.1016/j.neuropharm.2011.04.008] [Citation(s) in RCA: 181] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2010] [Revised: 04/01/2011] [Accepted: 04/06/2011] [Indexed: 11/23/2022]
Abstract
The median (MR) and dorsal raphe (DR) nuclei contain the majority of the 5-hydroxytryptamine (5-HT, serotonin) neurons that project to limbic forebrain regions, are important in regulating homeostatic functions and are implicated in the etiology and treatment of mood disorders and schizophrenia. The primary synaptic inputs within and to the raphe are glutamatergic and GABAergic. The DR is divided into three subfields, i.e., ventromedial (vmDR), lateral wings (lwDR) and dorsomedial (dmDR). Our previous work shows that cell characteristics of 5-HT neurons and the magnitude of the 5-HT(1A) and 5-HT(1B) receptor-mediated responses in the vmDR and MR are not the same. We extend these observations to examine the electrophysiological properties across all four raphe subfields in both 5-HT and non-5-HT neurons. The neurochemical topography of glutamatergic and GABAergic cell bodies and nerve terminals were identified using immunohistochemistry and the morphology of the 5-HT neurons was measured. Although 5-HT neurons possessed similar physiological properties, important differences existed between subfields. Non-5-HT neurons were indistinguishable from 5-HT neurons. GABA neurons were distributed throughout the raphe, usually in areas devoid of 5-HT neurons. Although GABAergic synaptic innervation was dense throughout the raphe (immunohistochemical analysis of the GABA transporters GAT1 and GAT3), their distributions differed. Glutamate neurons, as defined by vGlut3 anti-bodies, were intermixed and co-localized with 5-HT neurons within all raphe subfields. Finally, the dendritic arbor of the 5-HT neurons was distinct between subfields. Previous studies regard 5-HT neurons as a homogenous population. Our data support a model of the raphe as an area composed of functionally distinct subpopulations of 5-HT and non-5-HT neurons, in part delineated by subfield. Understanding the interaction of the cell properties of the neurons in concert with their morphology, local distribution of GABA and glutamate neurons and their synaptic input, reveals a more complicated and heterogeneous raphe. These results provide an important foundation for understanding how specific subfields modulate behavior and for defining which aspects of the circuitry are altered during the etiology of psychological disorders.
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Hansson C, Haage D, Taube M, Egecioglu E, Salomé N, Dickson SL. Central administration of ghrelin alters emotional responses in rats: behavioural, electrophysiological and molecular evidence. Neuroscience 2011; 180:201-11. [PMID: 21303683 DOI: 10.1016/j.neuroscience.2011.02.002] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2010] [Revised: 01/06/2011] [Accepted: 02/01/2011] [Indexed: 12/20/2022]
Abstract
The orexigenic and pro-obesity hormone ghrelin targets key hypothalamic and mesolimbic circuits involved in energy balance, appetite and reward. Given that such circuits are closely integrated with those regulating mood and cognition, we sought to determine whether chronic (>2 weeks) CNS exposure to ghrelin alters anxiety- and depression-like behaviour in rats as well as some physiological correlates. Rats bearing chronically implanted i.c.v. catheters were treated with ghrelin (10 μg/d) or vehicle for 4 weeks. Tests used to assess anxiety- and depression-like behaviour were undertaken during weeks 3-4 of the infusion. These revealed an increase in anxiety- and depression-like behaviour in the ghrelin-treated rats relative to controls. At the end of the 4-week infusion, brains were removed and the amygdala dissected for subsequent qPCR analysis that revealed changes in expression of a number of genes representing key systems implicated in these behavioural changes. Finally, given the key role of the dorsal raphe serotonin system in emotional reactivity, we examined the electrophysiological response of dorsal raphe neurons after a ghrelin challenge, and found mainly inhibitory responses in this region. We demonstrate that the central ghrelin signalling system is involved in emotional reactivity in rats, eliciting pro-anxiety and pro-depression effects and have begun to explore novel target systems for ghrelin that may be of importance for these effects.
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Affiliation(s)
- C Hansson
- Department of Physiology/Endocrinology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at the University of Gothenburg, Medicinaregatan 11, SE-40530 Gothenburg, Sweden
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Jennings KA, Lesch KP, Sharp T, Cragg SJ. Non-linear relationship between 5-HT transporter gene expression and frequency sensitivity of 5-HT signals. J Neurochem 2010; 115:965-73. [PMID: 20854367 DOI: 10.1111/j.1471-4159.2010.07001.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Much evidence suggests that variation in expression of the 5-hydroxytryptamine (5-HT) transporter (5-HTT) is linked to risk of psychiatric illness, but the neurobiological basis of this association is uncertain. In this study, we investigated the impact of variation in 5-HTT expression on subsecond fluctuations in extracellular 5-HT concentrations ([5-HT](o) ). Stimulus-evoked [5-HT](o) was detected using fast-scan cyclic voltammetry at carbon-fibre microelectrodes in the substantia nigra in brain slices from 5-HTT knockout (KO) and 5-HTT over-expressing (OE) mice. Compared with wild-type (WT) controls, evoked [5-HT](o) was greater in KO and less in OE mice. In WT controls, evoked [5-HT](o) was frequency-sensitive; however, in both KO and OE mice, evoked [5-HT](o) showed a striking loss of frequency sensitivity. The latter was observed in WT mice after application of a 5-HTT blocker. These data show that while variation in 5-HTT expression modified the peak magnitude of [5-HT](o) evoked by any given stimulus in a gene dose dependent manner, there was a non-linear relationship between 5-HTT expression and frequency sensitivity. Overall, the findings suggest that variation in 5-HTT expression has a marked effect on frequency sensitivity which is a fundamental property of normal 5-HT transmission.
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Ghanbari R, El Mansari M, Blier P. Electrophysiological effects of the co-administration of escitalopram and bupropion on rat serotonin and norepinephrine neurons. J Psychopharmacol 2010; 24:39-50. [PMID: 18719044 DOI: 10.1177/0269881108095714] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Clinical studies indicate that addition of bupropion to selective serotonin (5-HT) reuptake inhibitors (SSRIs) provides incremental benefit over SSRI monotherapy in depression. This study was designed to investigate the effects of co-administration of bupropion with escitalopram on the firing rate of 5-HT and norepinephrine (NE) neurons in anesthetized rats. Escitalopram (10 mg/kg/day x 2 days), given via subcutaneously (s.c.) implanted minipumps, decreased the firing of 5-HT and NE neurons by 70% and 55%, respectively. The firing of 5-HT neurons, unlike that of NE neurons, recovered after the 14-day escitalopram regimen. Bupropion, injected once daily (30 mg/kg/day, s.c. x 2 days), did not increase 5-HT firing but decreased that of NE by 55%. After 14 days of repeated bupropion administration, 5-HT firing was increased by 50%, and NE firing was back to baseline. Co-administration of escitalopram and bupropion doubled 5-HT firing after 2 and 14 days, whereas NE neurons were inhibited by 60% after 2 days, but partially recovered after 14 days. The responsiveness of 5-HT(1A) autoreceptors was significantly attenuated in the combination-treated rats after 2 days, indicating an early desensitization. These results provide support for contributions from 5-HT and NE mechanisms for enhanced effectiveness of combination of SSRI and bupropion treatment.
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Affiliation(s)
- R Ghanbari
- University of Ottawa, Institute of Mental Health Research, Ottawa Ontario, Canada.
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15
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Mendiguren A, Pineda J. Effect of the CB(1) receptor antagonists rimonabant and AM251 on the firing rate of dorsal raphe nucleus neurons in rat brain slices. Br J Pharmacol 2009; 158:1579-87. [PMID: 19845674 DOI: 10.1111/j.1476-5381.2009.00434.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND AND PURPOSE Previous studies have suggested a regulation of 5-hydroxytryptamine (5-HT) neurons by the endocannabinoid system. The aim of our work was to examine the effect of two CB(1) receptor antagonists, SR141716A (rimonabant, Sanofi-Synthélabo Recherche, Montpellier, France) and N-(piperidin-1-yl)-5-(4-iodophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide (AM251, Tocris Cookson, Bristol, UK), on the firing rate of dorsal raphe nucleus (DRN) neurons. EXPERIMENTAL APPROACH Single-unit extracellular recordings were performed to study the effect of CB(1) receptor antagonists in slices of the DRN from rat brain. KEY RESULTS Rimonabant (1 microM) and AM251 (1 microM) decreased the firing rate of about 50% of all the recorded DRN 5-HT cells. The GABA(A)receptor antagonist picrotoxin (20 microM) (Sigma) prevented and also reversed the inhibitory effect of rimonabant (1 microM) and AM251 (1 microM), suggesting that CB(1) receptors regulate 5-HT neurons through the GABAergic system. However, the CB(1)/CB(2) receptor agonist R-(+)-[2,3-dihydro-5-methyl-3-[(morpholinyl)-methyl]pyrrolol[1,2,3-de]-1,4-benzoxazinyl]-(1-naphthalenyl) methanone mesylate salt (10 microM) (WIN55212-2, Sigma, St. Louis, MO, USA) failed to change the firing activity of non-5-HT (presumably GABAergic) neurons in the DRN. The endocannabinoid N-(2-hydroxyethyl)-5Z,8Z,11Z,14Z-eicosatetraenamide (anandamide, Tocris Cookson) (10 microM) also inhibited the firing activity of a number of 5-HT neurons, but this inhibition was not blocked by rimonabant (1 microM) or AM251 (1 microM), and the stable analogue R-(+) N-(2-hydroxy-1methylethyl)-5Z,8Z,11Z,14Z-eicosatetraenamide (methanandamide, Tocris Cookson) (10 microM) did not mimic this effect. The selective CB(1) receptor agonist arachidonoyl-2-chloroethylamide (ACEA) (1 microM) only slightly increased the firing rate of DRN 5-HT cells. CONCLUSIONS AND IMPLICATIONS These results suggest a tonic/constitutive regulation of DRN 5-HT neurons by the endocannabinoid system, which may occur through a CB(1) receptor-mediated inhibition of the GABAergic system. The inhibitory effect of anandamide may be mediated through a CB(1) receptor-independent mechanism.
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Affiliation(s)
- Aitziber Mendiguren
- Department of Pharmacology, University of the Basque Country, Leioa, Bizkaia, Spain
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16
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Ghanbari R, El Mansari M, Shahid M, Blier P. Electrophysiological characterization of the effects of asenapine at 5-HT(1A), 5-HT(2A), alpha(2)-adrenergic and D(2) receptors in the rat brain. Eur Neuropsychopharmacol 2009; 19:177-87. [PMID: 19116183 DOI: 10.1016/j.euroneuro.2008.11.001] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/08/2008] [Revised: 09/23/2008] [Accepted: 11/04/2008] [Indexed: 10/21/2022]
Abstract
Asenapine is a psychopharmacologic agent being developed for schizophrenia and bipolar disorder. This study electrophysiologically characterized the in vivo effects of asenapine at dorsal raphe nucleus (DRN) and hippocampus serotonin-1A (5-HT(1A)), ventral tegmental area D(2), locus coeruleus 5-HT(2A,) and alpha(2)-adrenergic receptors in anesthetized rats. Asenapine displayed potent antagonistic activity at alpha(2)-adrenoceptors (ED(50), 85+/-2 microg/kg), 5-HT(2A) (ED(50), 75+/-2 microg/kg) and D(2) receptors (ED(50), 40+/-2 microg/kg) as evidenced by its reversal of clonidine-, DOI-, and apomorphine-induced inhibition of norepinephrine and dopamine neurons. In contrast, asenapine acted as a partial agonist at 5-HT(1A) receptors in DRN and hippocampus, as indicated by blockade of its inhibitory effect on neuronal firing by the 5-HT(1A) antagonist WAY 100635 and the partial inhibition of the suppressant action of 5-HT when co-applied by microiontophoresis. These results confirm that asenapine displays potent antagonistic activity at 5-HT(2A), D(2), alpha(2)-adrenergic receptors and provide evidence to support its 5-HT(1A) partial agonistic activity.
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Affiliation(s)
- Ramez Ghanbari
- University of Ottawa Institute of Mental Health Research, 1145 Carling Avenue, Ottawa, Ontario K1Z7K4, Canada.
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17
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Sustained administration of pramipexole modifies the spontaneous firing of dopamine, norepinephrine, and serotonin neurons in the rat brain. Neuropsychopharmacology 2009; 34:651-61. [PMID: 18688211 DOI: 10.1038/npp.2008.114] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Pramipexole (PPX) is a D(2)/D(3) receptor agonist that has been shown to be effective in the treatment of depression. Serotonin (5-HT), norepinephrine (NE) and dopamine (DA) systems are known to be involved in the pathophysiology and treatment of depression. Due to reciprocal interactions between these neuronal systems, drugs selectively targeting one system-specific receptor can indirectly modify the firing activity of neurons that contribute to firing patterns in systems that operate via different neurotransmitters. It was thus hypothesized that PPX would alter the firing rate of DA, NE and 5-HT neurons. To test this hypothesis, electrophysiological experiments were carried out in anesthetized rats. Subcutaneously implanted osmotic minipumps delivered PPX at a dose of 1 mg/kg per day for 2 or 14 days. After a 2-day treatment with PPX the spontaneous neuronal firing of DA neurons was decreased by 40%, NE neuronal firing by 33% and the firing rate of 5-HT neurons remained unaltered. After 14 days of PPX treatment, the firing rate of DA had recovered as well as that of NE, whereas the firing rate of 5-HT neurons was increased by 38%. It was also observed that sustained PPX administration produced desensitization of D(2)/D(3) and 5-HT(1A) cell body autoreceptors, as well as a decrease in sensitivity of alpha(2)-adrenergic cell body autoreceptors. These adaptive changes are implicated in long-term firing rate adaptations of DA, NE and 5-HT neurons after prolonged PPX administration. In conclusion, the therapeutic action of PPX in depression might be attributed to increased DA and 5-HT neurotransmission.
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18
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Threlfell S, Exley R, Cragg SJ, Greenfield SA. Constitutive histamine H2 receptor activity regulates serotonin release in the substantia nigra. J Neurochem 2008; 107:745-55. [PMID: 18761715 DOI: 10.1111/j.1471-4159.2008.05646.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The substantia nigra pars reticulata (SNr) forms a principal output from the basal ganglia. It also receives significant histamine (HA) input from the tuberomammillary nucleus whose functions in SNr remain poorly understood. One identified role is the regulation of serotonin (5-HT) neurotransmission via the HA-H(3) receptor. Here we have explored regulation by another HA receptor expressed in SNr, the H(2)-receptor (H(2)R), by monitoring electrically evoked 5-HT release with fast-scan cyclic voltammetry at carbon-fiber microelectrodes in SNr in rat brain slices. Selective H(2)R antagonists (inverse agonists) ranitidine and tiotidine enhanced 5-HT release while the agonist amthamine suppressed release. The 'neutral' competitive antagonist burimamide alone was without effect but prevented ranitidine actions indicating that inverse agonist effects result from constitutive H(2)R activity independent of HA tone. H(2)R control of 5-HT release was most apparent (from inverse agonist effects) at lower frequencies of depolarization (< or = 20 Hz), and prevailed in the presence of antagonists of GABA, glutamate or H(3)-HA receptors. These data reveal that H(2)Rs in SNr are constitutively active and inhibit 5-HT release through H(2)Rs on 5-HT axons. These data may have therapeutic implications for Parkinson's disease, when SNr HA levels increase, and for neuropsychiatric disorders in which 5-HT is pivotal.
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Affiliation(s)
- Sarah Threlfell
- Department of Pharmacology, University of Oxford, Oxford, UK.
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19
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El Mansari M, Ghanbari R, Janssen S, Blier P. Sustained administration of bupropion alters the neuronal activity of serotonin, norepinephrine but not dopamine neurons in the rat brain. Neuropharmacology 2008; 55:1191-8. [PMID: 18708076 DOI: 10.1016/j.neuropharm.2008.07.028] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2008] [Revised: 06/13/2008] [Accepted: 07/21/2008] [Indexed: 11/28/2022]
Abstract
Bupropion is widely used in the treatment of depression. There are, however, limited data on its long-term effects on monoaminergic neurons and therefore the mechanism of its delayed onset of action is at present not well understood. The present study was conducted to examine the effects of prolonged bupropion administration on the firing activity of dorsal raphe nucleus (DRN), locus coeruleus (LC), and ventral tegmental area (VTA) neurons. Spontaneously firing neurons were recorded extracellularly in rats anesthetized with chloral hydrate. Bupropion (30 mg/kg/day) was administered using subcutaneously implanted minipumps. In the DRN, the firing rate of serotonin (5-HT) neurons was significantly increased after 2, 7 and 14 days of administration. The suppressant effect of LSD was significantly diminished after the two-day regimen, indicating a desensitization of 5-HT1A autoreceptors. In the LC, the firing rate of norepinephrine (NE) neurons was significantly attenuated after a 2-day regimen, but recovered progressively over 14 days of administration. The suppressant effect of clonidine on NE neuronal firing was significantly attenuated in rats treated with bupropion for 14 days, indicating a desensitization of alpha2-adrenoceptors. In the VTA, neither 2 nor 14 days of bupropion administration altered the firing and burst activity of dopamine neurons. These results indicate that bupropion, unlike 5-HT reuptake inhibitors, promptly increased 5-HT neuronal activity, due to early desensitization of the 5-HT1A autoreceptor. The gradual recovery of neuronal firing of NE neurons, due to the desensitization of alpha2-adrenoceptors, in the presence of the sustained increase in 5-HT neuronal firing, may explain in part the delayed onset of action of bupropion in major depression.
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Affiliation(s)
- Mostafa El Mansari
- University of Ottawa Institute of Mental Health Research, Room 7407, 1145 Carling Avenue, Ottawa, Ontario, Canada K1Z 7K4.
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20
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Hajós M, Allers KA, Jennings K, Sharp T, Charette G, Sík A, Kocsis B. Neurochemical identification of stereotypic burst-firing neurons in the rat dorsal raphe nucleus using juxtacellular labelling methods. Eur J Neurosci 2007; 25:119-26. [PMID: 17241273 DOI: 10.1111/j.1460-9568.2006.05276.x] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Recent electrophysiological studies have discovered evidence of heterogeneity of 5-hydroxytryptamine (5-HT) neurons in the mesencephalic raphe nuclei. Of particular interest is a subpopulation of putative 5-HT neurons that display many of the electrophysiological properties of presumed 5-HT-containing neurons (regular and slow firing of single spikes with a broad waveform) but fire spikes in short, stereotyped bursts. In the present study we investigated the chemical identity of these neurons in rats utilizing in vivo juxtacellular labelling methods. Of ten dorsal raphe nucleus (DRN) neurons firing short stereotyped bursts within an otherwise regular firing pattern, all exhibited immunoreactivity for either 5-HT (n = 6) or the 5-HT synthesizing enzyme, tryptophan hydroxylase (TRH; n = 2) or both (n = 2). Supporting pharmacological experiments demonstrated that the burst firing DRN neurons demonstrated equal sensitivity to 5-HT(1A) agonism and alpha(1)-adrenoceptor antagonism to single spiking DRN neurons that we have previously identified as 5-HT-containing. Collectively these data provide direct evidence that DRN neurons that exhibit stereotyped burst firing activity are 5-HT containing. The presence of multiple types of electrophysiologically distinct midbrain 5-HT neurons is discussed.
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Affiliation(s)
- Mihály Hajós
- Oxford University Department of Pharmacology, Mansfield Road, Oxford, OX2 6HE, UK.
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21
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Burdakov D, Alexopoulos H, Vincent A, Ashcroft FM. Low-voltage-activated A-current controls the firing dynamics of mouse hypothalamic orexin neurons. Eur J Neurosci 2005; 20:3281-5. [PMID: 15610160 PMCID: PMC5767115 DOI: 10.1111/j.1460-9568.2004.03815.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The activity of hypothalamic neurons that release the neuropeptides orexin-A and orexin-B is essential for normal wakefulness. Orexin neurons fire spontaneously and are hyperpolarized and inhibited by physiological neuromodulators, but the intrinsic determinants of their electrical activity are poorly understood. We show that mouse orexin neurons coexpress orexin-A and orexin-B, and possess a low-voltage-activated A-type K(+) current (A-current) likely to be composed of Kv4.3 subunits. The A-current enhances the inhibitory influence of hyperpolarizing currents via two mechanisms: by delaying the resumption of spiking after hyperpolarization and by increasing the slope of the relation between the firing frequency and injected current. These results identify an important determinant of the firing dynamics of orexin neurons, and support the idea that the A-current can control neuronal gain.
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Affiliation(s)
- Denis Burdakov
- Laboratory of Physiology, University of Oxford, Oxford, United Kingdom.
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22
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Gartside SE, Johnson DA, Leitch MM, Troakes C, Ingram CD. Early life adversity programs changes in central 5-HT neuronal function in adulthood. Eur J Neurosci 2003; 17:2401-8. [PMID: 12814371 DOI: 10.1046/j.1460-9568.2003.02668.x] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Early life adversity is associated with an increased incidence of psychiatric illness in adulthood. Although the mechanisms underlying this association are unclear, one possible substrate is brain 5-hydroxytryptamine neurotransmission, which is reportedly abnormal in several psychiatric disorders. This study examined the effect of a rat model of early life adversity, early maternal separation, on 5-hydroxytryptamine neurotransmission in adulthood. In vitro electrophysiological experiments revealed that, in early maternal separation rats compared with controls, the sensitivity of alpha1-adrenoceptors on 5-hydroxytryptamine neurons in the dorsal raphe nucleus was significantly reduced, whilst the sensitivity of 5-hydroxytryptamine1A receptors showed a nonsignificant trend to reduction. In in vivo microdialysis experiments, the 5-hydroxytryptamine1A receptor agonist-induced suppression of 5-hydroxytryptamine release in the frontal cortex was reduced in early maternal separation animals, suggesting desensitization of 5-hydroxytryptamine1A autoreceptors. There was no increase in basal 5-hydroxytryptamine in the frontal cortex as measured by microdialysis and a nonsignificant trend towards increased basal firing activity of classical (non-bursting) 5-hydroxytryptamine neurons in the dorsal raphe nucleus measured by in vivo electrophysiology. Finally, early maternal separation failed to alter expression of messenger ribonucleic acids coding for 5-hydroxytryptamine1A or alpha1B receptors in the dorsal raphe nucleus as measured by in situ hybridization histochemistry, suggesting that functional changes in receptor sensitivity observed are not due to changes in receptor gene transcription. The findings demonstrate that early life adversity programs changes in sensitivity of the two principal regulators of 5-hydroxytryptamine neuronal activity. Similar effects in humans may contribute to the increased incidence of psychiatric illness in individuals exposed to early life adversity.
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MESH Headings
- 8-Hydroxy-2-(di-n-propylamino)tetralin/pharmacology
- Adrenergic alpha-Agonists/pharmacology
- Analysis of Variance
- Animals
- Animals, Newborn
- Autoradiography
- Brain/physiopathology
- Disease Models, Animal
- Dose-Response Relationship, Drug
- Electrophysiology/methods
- Free Radical Scavengers
- Frontal Lobe/drug effects
- Frontal Lobe/metabolism
- In Situ Hybridization
- In Vitro Techniques
- Maternal Deprivation
- Microdialysis/methods
- Neurons/physiology
- Phenylephrine/pharmacology
- Psychotic Disorders/etiology
- Raphe Nuclei/drug effects
- Raphe Nuclei/physiology
- Rats
- Receptors, Adrenergic, alpha-1/genetics
- Receptors, Adrenergic, alpha-1/metabolism
- Receptors, Serotonin/genetics
- Receptors, Serotonin/metabolism
- Receptors, Serotonin, 5-HT1
- Serotonin/physiology
- Serotonin Receptor Agonists/pharmacology
- Time Factors
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Affiliation(s)
- Sarah E Gartside
- Psychobiology Research Group, School of Neurology, Neurobiology and Psychiatry, University of Newcastle, The Medical School, Framlington Place, Newcastle upon Tyne NE2 4HH, UK.
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23
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Abstract
Substance P receptor [neurokinin 1 (NK1] antagonists (SPAs) represent a novel mechanistic approach to antidepressant therapy with comparable clinical efficacy to selective serotonin reuptake inhibitors (SSRIs). Because SSRIs are thought to exert their therapeutic effects by enhancing central serotonergic function, we have examined whether SPAs regulate neuronal activity in the dorsal raphe nucleus (DRN), the main source of serotonergic projections to the forebrain. Using in vivo electrophysiological techniques in the guinea pig, we found that administration of the highly selective NK1 receptor antagonist 1-(5-[[(2R,3S)-2-([(1R)-1-[3,5-bis(trifluoromethyl)phenyl]ethyl]oxy)-3-(4-phenyl)morpholin-4-yl]methyl]-2H-1,2,3-triazol-4-yl)-N,N-dimethylmethanamine (L-760735) caused an increase in DRN neuronal firing rate. However, unlike chronic treatment with fluoxetine, there was no detectable 5-HT1A autoreceptor desensitization. In vitro electrophysiological investigation showed that these effects were not mediated by a direct action in the DRN, an observation supported by immunocytochemical analysis that identified the lateral habenula (LHb) as a more likely site of action. Subsequently, we found that local application of L-760735 into the LHb increased firing in the DRN, which, together with our data showing that L-760735 increased metabolic activity in the cingulate cortex, amygdala, LHb, and DRN, indicates that the effects of L-760735 may be mediated by disinhibition of forebrain structures acting via a habenulo raphe projection. These findings support other evidence for an antidepressant profile of SPAs and suggest that regulation of DRN neuronal activity may contribute to their antidepressant mechanism of action but in a manner that is distinct from monoamine reuptake inhibitors.
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24
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Varga V, Székely AD, Csillag A, Sharp T, Hajós M. Evidence for a role of GABA interneurones in the cortical modulation of midbrain 5-hydroxytryptamine neurones. Neuroscience 2002; 106:783-92. [PMID: 11682163 DOI: 10.1016/s0306-4522(01)00294-9] [Citation(s) in RCA: 121] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Recent electrophysiological studies demonstrate that the ventral medial prefrontal cortex has a powerful inhibitory influence on 5-hydroxytryptamine (5-HT) neurones in the dorsal raphe nucleus. Here we utilised a combination of anatomical and electrophysiological methods to characterise the cellular substrate underlying this effect.Anterograde tracing (Phaseolus vulgaris leucoagglutinin) using electron microscopy demonstrated a pathway from the ventral medial prefrontal cortex that makes neuronal contacts throughout the dorsal raphe nucleus. These contacts were predominantly asymmetrical synapses adjoining GABA immunoreactive dendrites and spines. In vivo extracellular recordings were made in the dorsal raphe nucleus of the anaesthetised rat from a subpopulation of non-5-HT neurones. These neurones were fast-firing, irregular and with short spike width, properties strongly reminiscent of immunochemically identified GABA interneurones in other brain regions. Recordings of classical 5-HT neurones were also included. Electrical stimulation of the ventral medial prefrontal cortex elicited a rapid onset (16 ms latency), orthodromic excitation of the non-5-HT neurones (13/25 neurones). This stimulation also caused a pronounced inhibition of most 5-HT neurones tested, with a longer latency (30 ms), and this was partially blocked by locally applied bicuculline. These data provide the first evidence that the ventral medial prefrontal cortex influences the activity of large numbers of raphe 5-HT neurones by targeting a local network of GABA neurones. This circuitry predicts that physiological and pathological changes in the ventral medial prefrontal cortex will impact on significant parts of the forebrain 5-HT system.
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Affiliation(s)
- V Varga
- Department of Anatomy, Semmelweis University Budapest, Hungary
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25
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Li YQ, Li H, Kaneko T, Mizuno N. Morphological features and electrophysiological properties of serotonergic and non-serotonergic projection neurons in the dorsal raphe nucleus. An intracellular recording and labeling study in rat brain slices. Brain Res 2001; 900:110-8. [PMID: 11325353 DOI: 10.1016/s0006-8993(01)02272-7] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The morphology and electrophysiological properties of serotonergic and non-serotonergic projection neurons in the dorsal raphe nucleus (DRN) of the rat were examined in frontal brain slices. Biocytin was injected intracellularly into the intracellularly recorded neurons. Then the morphology of the recorded neurons was observed after histochemical visualization of biocytin. The recorded neurons extending their main axons outside the DRN were considered as projection neurons. Subsequently, serotonergic nature of the neurons was examined by serotonin (5-HT) immunohistochemistry. The general form of the dendritic trees is radiant and poorly branching in both 5-HT- and non-5-HT neurons. However, the dendrites of the 5-HT neurons were spiny, whereas those of the non-5-HT neurons were aspiny. The main axons of both 5-HT- and non-5-HT neurons were observed to send richly branching axon collaterals to the DRN, ventrolateral part of the periaqueductal gray and the midbrain tegmentum. In response to weak, long depolarizing current pulses, the 5-HT neurons displayed a slow and regular firing activity. The non-5-HT neurons fired at higher frequencies even when stronger current was injected. Some other differences in electrophysiological properties were also observed between the 5-HT-immunoreactive spiny projection neurons and the 5-HT-immunonegative aspiny projection neurons.
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Affiliation(s)
- Y Q Li
- Department of Anatomy and K.K. Leung Brain Research Centre, The Fourth Military Medical University, 710032, People's Republic of, Xi'an, China
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26
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Gartside SE, Hajós-Korcsok E, Bagdy E, Hársing LG, Sharp T, Hajós M. Neurochemical and electrophysiological studies on the functional significance of burst firing in serotonergic neurons. Neuroscience 2000; 98:295-300. [PMID: 10854760 DOI: 10.1016/s0306-4522(00)00060-9] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
We have previously described a population of 5-hydroxytryptamine neurons which repetitively fires bursts of usually two (but occasionally three or four) action potentials, with a short (<20 ms) interspike interval within a regular low-frequency firing pattern. Here we used a paradigm of electrical stimulation comprising twin pulses (with 7- or 10-ms inter-pulse intervals) to mimic this burst firing pattern, and compared the effects of single- and twin-pulse electrical stimulations in models of pre- and postsynaptic 5-hydroxytryptamine function. Firstly, we measured the effect of direct electrical stimulation (2 Hz for 2 min) of rat brain slices on efflux of preloaded [3H]5-hydroxytryptamine. In this in vitro model, twin-pulse stimulation increased the efflux of tritium by about twice as much as did single-pulse stimulation. This effect was evident in the medial prefrontal cortex (area under the curve: 2. 59+/-0.34 vs 1.28+/-0.22% relative fractional release), as well as in the caudate-putamen (3.93+/-0.65 vs 2.17+/-0.51%) and midbrain raphe nuclei (5.42+/-1.05 vs 2.51+/-0.75%). Secondly, we used in vivo microdialysis to monitor changes in endogenous extracellular 5-hydroxytryptamine in rat medial prefrontal cortex in response to electrical stimulation (3 Hz for 10 min) of the dorsal raphe nucleus. In this model, twin-pulse stimulation of the dorsal raphe nucleus increased 5-hydroxytryptamine by approximately twice as much as did single-pulse stimulation at the same frequency (area under the curve: 50.4+/-9.0 vs 24.2+/-4.4 fmol). Finally, we used in vivo extracellular recording to follow the response of postsynaptic neurons in the rat medial prefrontal cortex to 5-hydroxytryptamine released by dorsal raphe stimulation. Electrical stimulation of the dorsal raphe nucleus (1 Hz) induced a clear-cut poststimulus inhibition in the majority of cortical neurons tested. In these experiments, the duration of poststimulus inhibition following twin-pulse stimulation was markedly longer than that induced by single-pulse stimulation (200+/-21 vs 77+/-18.5 ms). Taken together, the present in vitro and in vivo data suggest that in 5-hydroxytryptamine neurons, short bursts of action potentials will propagate along the axon to the nerve terminal and will enhance both the release of 5-hydroxytryptamine and its postsynaptic effect.
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Affiliation(s)
- S E Gartside
- Oxford University Department of Clinical Pharmacology, Radcliffe Infirmary, Woodstock Road, Oxford, OX2 6HE, UK
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Morzorati SL, Johnson TB. Serotonergic Neuronal Activity in the Dorsal Raphe Nucleus of Selectively Bred Alcohol-Preferring and Alcohol-Nonpreferring Rats and Unselected Wistar Rats. Alcohol Clin Exp Res 1999. [DOI: 10.1111/j.1530-0277.1999.tb04358.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Hajós M, Richards CD, Székely AD, Sharp T. An electrophysiological and neuroanatomical study of the medial prefrontal cortical projection to the midbrain raphe nuclei in the rat. Neuroscience 1998; 87:95-108. [PMID: 9722144 DOI: 10.1016/s0306-4522(98)00157-2] [Citation(s) in RCA: 224] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
In this study we utilized electrophysiological and pathway tracing methods to investigate the projections from the medial prefrontal cortex to the midbrain raphe nuclei of the rat. Initial pathway tracing experiments using retrograde (horseradish peroxidase conjugates with wheatgerm agglutinin or choleratoxin B subunit) and anterograde (Phaseolus vulgaris-leucoagglutinin) markers demonstrated a direct, bilateral projection to the dorsal raphe nucleus and median raphe nucleus from the medial prefrontal cortex, and the origin of this projection was localized predominantly in the ventral medial prefrontal cortex (infralimbic/dorsal penduncular cortices). Using chloral hydrate-anaesthetized rats, extracellular recordings were made mostly from 5-hydroxytryptamine neurons in the dorsal raphe nucleus, but non-5-hydroxytryptamine dorsal raphe neurons were also studied, as was a small number of 5-hydroxytryptamine neurons in the median raphe nucleus. In an initial study, electrical stimulation of the ventral medial prefrontal cortex caused a post-stimulus inhibition in the majority (49/56) of dorsal raphe 5-hydroxytryptamine neurons tested (mean duration of inhibition, 200+/-17 ms); in some cases (8/56) the inhibition was preceded by short-latency (26 +/-3 ms) orthodromic activation, and a small number of cells was antidromically activated (6/56). Both single spiking and burst-firing 5-hydroxytryptamine neurons in the dorsal raphe nucleus responded in the same way, and median raphe 5-hydroxytryptamine neurons were also inhibited (5/5). In contrast, few (2/12) of the non-5-hydroxytryptamine dorsal raphe neurons tested were inhibited by ventral medial prefrontal cortex stimulation. The effects of stimulation of the dorsal and ventral medial prefrontal cortex were compared on the same raphe 5-hydroxytryptamine neurons (n=17): ventral medial prefrontal cortex stimulation inhibited 16/17 of these neurons while only 8/17 were inhibited by dorsal medial prefrontal cortex stimulation. Finally, the inhibitory effect of ventral medial prefrontal cortex stimulation on 5-hydroxytryptamine cell-firing was not altered by 5-hydroxytryptamine depletion with p-chlorophenylalanine or by systemic administration of the selective 5-hydroxytryptamine1A receptor antagonist WAY 100635. The latter findings indicate that the inhibition is not due to release of raphe 5-hydroxytryptamine which could theoretically arise from anti- or orthodromically activated 5-hydroxytryptamine neurons. Our results show that stimulation of the ventral medial prefrontal cortex causes a marked post-stimulus inhibition in the vast majority of midbrain raphe 5-hydroxytryptamine neurons tested. It seems likely that the projection from ventral medial prefrontal cortex to the midbrain raphe nuclei mediates the responses of 5-hydroxytryptamine neurons to cortical stimulation. These data are relevant to recent discoveries of functional and structural abnormalities in the medial prefrontal cortex of patients with major depressive illness.
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Affiliation(s)
- M Hajós
- Department of Clinical Pharmacology, Radcliffe Infirmary, University of Oxford, UK
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Hajós M, Sharp T, Newberry NR. Intracellular recordings from burst-firing presumed serotonergic neurones in the rat dorsal raphe nucleus in vivo. Brain Res 1996; 737:308-12. [PMID: 8930381 DOI: 10.1016/0006-8993(96)00936-5] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Here we report the existence of burst-firing neurones in the rat dorsal raphe as detected in vivo using intracellular electrophysiological techniques. These neurones discharged single action potentials and doublets or triplets of action potentials in a slow and regular pattern. The apparent input resistance, action potential width and firing threshold of these burst-firing raphe neurones were indistinguishable from classical 5-HT neurones. Spike doublets were evoked by depolarising DC currents, but only in burst-firing neurones. These findings provide further evidence to support the hypothesis that 5-HT neurones (or a sub-set of them) are capable of burst-firing activity.
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Affiliation(s)
- M Hajós
- Oxford University Department of Clinical Pharmacology, Radcliffe Infirmary, UK.
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