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Wu S, Zhong G, Su Q, Hu T, Rao G, Li T, Wu Y, Ruan Z, Zhang H, Tang Z, Hu L. Arsenic induced neurotoxicity in the brain of ducks: The potential involvement of the gut-brain axis. J Trace Elem Med Biol 2024; 81:127336. [PMID: 37976960 DOI: 10.1016/j.jtemb.2023.127336] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/14/2022] [Revised: 08/05/2023] [Accepted: 10/31/2023] [Indexed: 11/19/2023]
Abstract
BACKGROUND Arsenic is a widely distributed ecotoxic pollutant that has been found to cause neurotoxicity in a variety of species. Gut-brain axis is a two-way information network between the gut microbiome and the brain, which is closely related to organismal health. However, the role of the gut-brain axis in arsenic-induced neurotoxicity remains largely unknown. METHODS In order to explore whether there is a relationship between brain and gut microbiota of meat ducks, we performed molecular biological detection including RT-qPCR and Western blot, as well as morphological detection including, HE staining and immunohistochemistry. Meanwhile, intestinal contents were analyzed using 16 S ribosomal RNA gene sequencing and analysis RESULTS: In this study, we investigated whether arsenic trioxide (ATO) can activate the gut microbiome-brain axis to induce intestinal and brain injury. The results showed that ATO-exposure disrupted the diversity balance of intestinal microbiota and integrity and injured the intestinal structure. ATO-exposure also reduced the number of glycogen and goblet cells in the duodenum. In addition, exposure to ATO caused intestinal inflammatory injury by activating NF-κB signaling pathway and promoting the expression of its target genes. Meanwhile, the tight junction-related proteins (ZO-1, occludin) of gut and brain were reduced by ATO exposure. Furthermore, results also revealed that ATO-exposure induced brain injury, including neuronal cell vacuolization and reduced numbers of neuronal cells in the cortex and hippocampus. Remarkably, ATO-exposure also disrupted neurotransmitter levels. Additionally, our further molecular mechanism study revealed that ATO-exposure increased the expression of autophagy and apoptosis related mRNA and proteins levels in the brain tissues. CONCLUSION Altogether, these findings provide a new insight into that ATO-exposure induced intestinal injury and aggravated neurotoxicity via the gut-brain axis.
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Affiliation(s)
- Shaofeng Wu
- College of Veterinary Medicine, South China Agricultural University, Guangzhou 510642, PR China
| | - Gaolong Zhong
- College of Veterinary Medicine, South China Agricultural University, Guangzhou 510642, PR China
| | - Qian Su
- College of Veterinary Medicine, South China Agricultural University, Guangzhou 510642, PR China
| | - Ting Hu
- College of Veterinary Medicine, South China Agricultural University, Guangzhou 510642, PR China
| | - Gan Rao
- College of Veterinary Medicine, South China Agricultural University, Guangzhou 510642, PR China
| | - Tong Li
- College of Veterinary Medicine, South China Agricultural University, Guangzhou 510642, PR China
| | - Yuhan Wu
- College of Veterinary Medicine, South China Agricultural University, Guangzhou 510642, PR China
| | - Zhiyan Ruan
- School of Pharmacy, Guangdong Food & Drug Vocational College, No. 321Longdong North Road, Tianhe District, Guangzhou 510520 Guangdong Province, PR China
| | - Hui Zhang
- College of Veterinary Medicine, South China Agricultural University, Guangzhou 510642, PR China
| | - Zhaoxin Tang
- College of Veterinary Medicine, South China Agricultural University, Guangzhou 510642, PR China
| | - Lianmei Hu
- College of Veterinary Medicine, South China Agricultural University, Guangzhou 510642, PR China.
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Park YS, Oh H, Sung KW. Atypical antidepressant mirtazapine inhibits 5-hydroxytryptamine3 receptor currents in NCB-20 cells. J Pharmacol Sci 2023; 151:63-71. [PMID: 36707180 DOI: 10.1016/j.jphs.2022.12.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2022] [Revised: 11/28/2022] [Accepted: 12/05/2022] [Indexed: 12/12/2022] Open
Abstract
Mirtazapine, an atypical antidepressant, is known to enhance serotonergic transmission by inhibiting the 5-hydroxytryptamine (5-HT)1A, 5-HT2C, and 5-HT3 receptors. However, the mechanism of action on the 5-HT3 receptor remains unclear. We investigated the inhibitory mechanisms of mirtazapine on 5-HT3 receptors of NCB20 neuroblastoma cells using the whole-cell voltage-clamp method. Mirtazapine inhibited the 5-HT3 receptor currents in a concentration-dependent manner, and the inhibitory effect was influenced by the concentration of 5-HT. When mirtazapine was co-applied to 5-HT, the maximal response of the 5-HT3 receptor current was reduced and EC50 was increased, suggesting that mirtazapine might act as a non-competitive inhibitor. Inhibition of 5-HT3 current by mirtazapine was stronger in pre-application than in co-application, which suggests that mirtazapine might act as a closed state inhibitor. This finding was further supported by no use-dependency of the mirtazapine for 5-HT3 receptor inhibition. Finally, mirtazapine accelerated the desensitization and deactivation process in a concentration-dependent manner. The difference in recovery time showed that mirtazapine drastically influences the desensitization process than the deactivation process. These mechanistic characteristics of mirtazapine support the understanding of the relationship between the 5-HT3 receptor and atypical antidepressants.
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Affiliation(s)
- Yong Soo Park
- Department of Anatomy, The Catholic University of Korea, 222 Banpo-daero, Seocho-gu, Seoul 06591, South Korea.
| | - Haejung Oh
- Department of Pharmacology, The Catholic University of Korea, 222 Banpo-daero, Seocho-gu, Seoul 06591, South Korea.
| | - Ki-Wug Sung
- Department of Pharmacology, The Catholic University of Korea, 222 Banpo-daero, Seocho-gu, Seoul 06591, South Korea.
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3
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Martinello K, Sucapane A, Fucile S. 5-HT3 Receptors in Rat Dorsal Root Ganglion Neurons: Ca 2+ Entry and Modulation of Neurotransmitter Release. LIFE (BASEL, SWITZERLAND) 2022; 12:life12081178. [PMID: 36013357 PMCID: PMC9409985 DOI: 10.3390/life12081178] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Revised: 07/29/2022] [Accepted: 07/31/2022] [Indexed: 11/16/2022]
Abstract
Rat dorsal root ganglion (DRG) neurons express 5-hydroxytryptamine receptors (5-HT3Rs). To elucidate their physiological role in the modulation of sensory signaling, we aimed to quantify their functional expression in newborn and adult rat DRG neurons, as well as their ability to modulate the Ca2+-dependent neurotransmitter release, by means of electrophysiological techniques combined with fluorescence-based Ca2+ imaging. The selective 5-HT3R agonist mCPBG (10 μM) elicited whole-cell currents in 92.5% of adult DRG neurons with a significantly higher density current than in responding newborn cells (52.2%), suggesting an increasing serotoninergic modulation on primary afferent cells during development. Briefly, 5-HT3Rs expressed by adult DRG neurons are permeable to Ca2+ ions, with a measured fractional Ca2+ current (i.e., the percentage of total current carried by Ca2+ ions, Pf) of 1.0%, similar to the value measured for the human heteromeric 5-HT3A/B receptor (Pf = 1.1%), but lower than that of the human homomeric 5-HT3A receptor (Pf = 3.5%). mCPBG applied to co-cultures of newborn DRG and spinal neurons significantly increased the miniature excitatory postsynaptic currents (mEPSCs) frequency in a subset of recorded spinal neurons, even in the presence of Cd2+, a voltage-activated Ca2+ channel blocker. Considered together, our findings indicate that the Ca2+ influx through heteromeric 5-HT3Rs is sufficient to increase the spontaneous neurotransmitter release from DRG to spinal neurons.
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Affiliation(s)
| | - Antonietta Sucapane
- Department of Physiology and Pharmacology, Sapienza University of Rome, P.le Aldo Moro, 5, 00185 Rome, Italy;
| | - Sergio Fucile
- IRCCS Neuromed, Via Atinense, 86077 Pozzilli, Italy;
- Department of Physiology and Pharmacology, Sapienza University of Rome, P.le Aldo Moro, 5, 00185 Rome, Italy;
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4
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Lovinger DM, Mateo Y, Johnson KA, Engi SA, Antonazzo M, Cheer JF. Local modulation by presynaptic receptors controls neuronal communication and behaviour. Nat Rev Neurosci 2022; 23:191-203. [PMID: 35228740 PMCID: PMC10709822 DOI: 10.1038/s41583-022-00561-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/19/2022] [Indexed: 12/15/2022]
Abstract
Central nervous system neurons communicate via fast synaptic transmission mediated by ligand-gated ion channel (LGIC) receptors and slower neuromodulation mediated by G protein-coupled receptors (GPCRs). These receptors influence many neuronal functions, including presynaptic neurotransmitter release. Presynaptic LGIC and GPCR activation by locally released neurotransmitters influences neuronal communication in ways that modify effects of somatic action potentials. Although much is known about presynaptic receptors and their mechanisms of action, less is known about when and where these receptor actions alter release, especially in vivo. This Review focuses on emerging evidence for important local presynaptic receptor actions and ideas for future studies in this area.
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Affiliation(s)
- David M Lovinger
- Laboratory for Integrative Neuroscience, National Institute on Alcohol Abuse and Alcoholism, Bethesda, MD, USA.
| | - Yolanda Mateo
- Laboratory for Integrative Neuroscience, National Institute on Alcohol Abuse and Alcoholism, Bethesda, MD, USA
| | - Kari A Johnson
- Department of Pharmacology, Uniformed Services University of the Health Sciences, Bethesda, MD, USA
| | - Sheila A Engi
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Mario Antonazzo
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Joseph F Cheer
- Department of Psychiatry, University of Maryland School of Medicine, Baltimore, MD, USA
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5
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Lopes LT, Canto-de-Souza L, Baptista-de-Souza D, de Souza RR, Nunes-de-Souza RL, Canto-de-Souza A. The interplay between 5-HT 2C and 5-HT 3A receptors in the dorsal periaqueductal gray mediates anxiety-like behavior in mice. Behav Brain Res 2022; 417:113588. [PMID: 34547341 DOI: 10.1016/j.bbr.2021.113588] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Revised: 08/17/2021] [Accepted: 09/15/2021] [Indexed: 11/17/2022]
Abstract
The monoamine neurotransmitter serotonin (5-HT) modulates anxiety by its activity on 5-HT2C receptors (5-HT2CR) expressed in the dorsal periaqueductal gray (dPAG). Here, we investigated the presence of 5-HT3A receptors (5-HT3AR) in the dPAG, and the interplay between 5-HT2CR and 5-HT3AR in the dPAG in mediating anxiety-like behavior in mice. We found that 5-HT3AR is expressed in the dPAG and the blockade of these receptors using intra-dPAG infusion of ondansetron (5-HT3AR antagonist; 3.0 nmol) induced an anxiogenic-like effect. The activation of 5-HT3ABR by the infusion of mCPBG [1-(m-Chlorophenyl)-biguanide; 5-HT3R agonist] did not alter anxiety-like behaviors. In addition, blockade of 5-HT3AR (1.0 nmol) prevented the anxiolytic-like effect induced by the infusion of the 5-HT2CR agonist mCPP (1-(3-chlorophenyl) piperazine; 0.03 nmol). None of the treatment effects on anxiety-like behaviors altered the locomotor activity levels. The present results suggest that the anxiolytic-like effect exerted by serotonin activity on 5-HT2CR in the dPAG is modulated by 5-HT3AR expressed in same region.
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Affiliation(s)
- Luana Tenorio Lopes
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, The University of Calgary, Calgary, Alberta, Canada.
| | - Lucas Canto-de-Souza
- Laboratory of Pharmacology, School of Pharmaceutical Sciences, Univ. Estadual Paulista, UNESP, Araraquara, SP 14801-902, Brazil; Neuroscience and Behavioral Institute, Av. do Café, 2.450, 14050-220 Ribeirão Preto, SP, Brazil.
| | - Daniela Baptista-de-Souza
- Psychobiology Group/Department of Psychology/CECH-UFSCar, São Carlos, SP 13565-905, Brazil; Laboratory of Pharmacology, School of Pharmaceutical Sciences, Univ. Estadual Paulista, UNESP, Araraquara, SP 14801-902, Brazil; Neuroscience and Behavioral Institute, Av. do Café, 2.450, 14050-220 Ribeirão Preto, SP, Brazil.
| | - Rimenez Rodrigues de Souza
- The University of Texas at Dallas, School of Behavior and Brain Sciences, 800 West Campbell Road, Richardson, TX 75080-3021, United States; The University of Texas at Dallas, Texas Biomedical Device Center, 800 West Campbell Road, Richardson, TX 75080-3021, United States.
| | - Ricardo L Nunes-de-Souza
- Psychobiology Group/Department of Psychology/CECH-UFSCar, São Carlos, SP 13565-905, Brazil; Joint Graduate Program in Physiological Sciences UFSCar/UNESP, Rod. Washington Luís, Km 235, São Carlos, SP 13565-905, Brazil; Laboratory of Pharmacology, School of Pharmaceutical Sciences, Univ. Estadual Paulista, UNESP, Araraquara, SP 14801-902, Brazil; Neuroscience and Behavioral Institute, Av. do Café, 2.450, 14050-220 Ribeirão Preto, SP, Brazil.
| | - Azair Canto-de-Souza
- Psychobiology Group/Department of Psychology/CECH-UFSCar, São Carlos, SP 13565-905, Brazil; Joint Graduate Program in Physiological Sciences UFSCar/UNESP, Rod. Washington Luís, Km 235, São Carlos, SP 13565-905, Brazil; Graduate Program in Psychology UFSCar, Rod. Washington Luís, Km 235, São Carlos, SP 13565-905, Brazil; Neuroscience and Behavioral Institute, Av. do Café, 2.450, 14050-220 Ribeirão Preto, SP, Brazil.
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6
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Yu Y, Li JJ, He XQ, Lai ZY, Hao R, Qi Y, Cao DQ, Fu M, Ma H, Xie QC, Sun M, Huang ZL, Jin LJ, Sun HH, Lu N, Wang R, Yung WH, Huang Y. 5-HT3Rs Maintain Hippocampal LTP in a CB1R-GABA A -Dependent Manner for Spatial Memory. Br J Pharmacol 2022; 179:2969-2985. [PMID: 34997582 DOI: 10.1111/bph.15793] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Revised: 11/23/2021] [Accepted: 12/13/2021] [Indexed: 11/27/2022] Open
Abstract
BACKGROUND AND PURPOSE As the only ionotropic receptor in 5-HT receptor family, 5-HT3 receptor (5-HT3R) involves in psychiatric disorders and its modulators have potential therapeutic effects for cognitive impairment in these disorders. However, it remains unclear how 5-HT3Rs shape synaptic plasticity for memory function. EXPERIMENTAL APPROACH Extracellular as well as whole-cell recordings were used to monitor hippocampal long-term potentiation (LTP) and synaptic transmission in hippocampal slices from 5-HT3AR knock-out or 5-HT3AR-GFP mice. Immunocytochemistry, qRT-PCR and Western blot were used to measure receptor expression. We also assessed hippocampal dependent cognition and memory using the Morris water maze (MWM) and novel object recognition. KEY RESULTS We found that 5-HT3R dysfunction impaired hippocampal LTP in Schaffer collateral (SC)-CA1 pathway in hippocampal slices by facilitating GABAergic inputs in pyramidal cells. This effect was dependent on 5-HT3Rs on axon-terminals. It resulted from reduced expression and function of cannabinoid receptor 1 (CB1R) co-localized with 5-HT3Rs on axon terminals, which led to diminishment of tonic inhibition of GABA release by CB1Rs. Inhibition of CB1Rs mimicked the facilitation of GABAergic transmission by 5-HT3R disruption. Consequently, mice with hippocampal 5-HT3R disruption exhibited impaired spatial memory in Morris water maze tasks. CONCLUSION AND IMPLICATIONS These results suggest that 5-HT3Rs are crucial in enabling hippocampal synaptic plasticity via a novel CB1R-GABAA -dependent pathway to regulate spatial memory.
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Affiliation(s)
- Yan Yu
- Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration (Ministry of Education), Department of Physiology and Pharmacology, Tongji Hospital, School of Medicine, Tongji University, Shanghai, China.,Department of Pharmacy, The Fifth People's Hospital of Shanghai, Fudan University, Shanghai, China
| | - Jing-Jing Li
- Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration (Ministry of Education), Department of Physiology and Pharmacology, Tongji Hospital, School of Medicine, Tongji University, Shanghai, China
| | - Xiao-Qian He
- Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration (Ministry of Education), Department of Physiology and Pharmacology, Tongji Hospital, School of Medicine, Tongji University, Shanghai, China
| | - Zi-Ying Lai
- Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration (Ministry of Education), Department of Physiology and Pharmacology, Tongji Hospital, School of Medicine, Tongji University, Shanghai, China
| | - Rui Hao
- Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration (Ministry of Education), Department of Physiology and Pharmacology, Tongji Hospital, School of Medicine, Tongji University, Shanghai, China.,Department of Physiology and Pathophysiology, Shanghai Medical College, Fudan University, Shanghai, China
| | - Yu Qi
- Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration (Ministry of Education), Department of Physiology and Pharmacology, Tongji Hospital, School of Medicine, Tongji University, Shanghai, China.,Department of Physiology and Pathophysiology, Shanghai Medical College, Fudan University, Shanghai, China
| | - Dong-Qing Cao
- Department of Physiology and Pathophysiology, Shanghai Medical College, Fudan University, Shanghai, China
| | - Ming Fu
- Department of Biology, York University, Toronto, ON, Canada
| | - Hong Ma
- Department of Physiology and Pathophysiology, Shanghai Medical College, Fudan University, Shanghai, China
| | - Qiu-Chen Xie
- Department of Physiology and Pathophysiology, Shanghai Medical College, Fudan University, Shanghai, China
| | - Mu Sun
- GeneScience Pharmaceuticals Co., Ltd, Shanghai, China
| | - Zhi-Li Huang
- Department of Pharmacology, Shanghai Medical College, Fudan University, Shanghai, China
| | - Ling-Jing Jin
- Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration (Ministry of Education), Department of Physiology and Pharmacology, Tongji Hospital, School of Medicine, Tongji University, Shanghai, China
| | - Hui-Hui Sun
- Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration (Ministry of Education), Department of Physiology and Pharmacology, Tongji Hospital, School of Medicine, Tongji University, Shanghai, China
| | - Ning Lu
- Department of Physiology and Pathophysiology, Shanghai Medical College, Fudan University, Shanghai, China
| | - Rui Wang
- Department of Biology, York University, Toronto, ON, Canada
| | - Wing-Ho Yung
- School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong, China
| | - Ying Huang
- Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration (Ministry of Education), Department of Physiology and Pharmacology, Tongji Hospital, School of Medicine, Tongji University, Shanghai, China.,Department of Biology, York University, Toronto, ON, Canada
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7
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Jun SB, Ikeda SR, Sung JE, Lovinger DM. Ethanol induces persistent potentiation of 5-HT 3 receptor-stimulated GABA release at synapses on rat hippocampal CA1 neurons. Neuropharmacology 2021; 184:108415. [PMID: 33275959 PMCID: PMC11009934 DOI: 10.1016/j.neuropharm.2020.108415] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Revised: 11/23/2020] [Accepted: 11/24/2020] [Indexed: 11/18/2022]
Abstract
Several studies have shown that ethanol (EtOH) can enhance the activity of GABAergic synapses via presynaptic mechanisms, including in hippocampal CA1 neurons. The serotonin type 3 receptor (5-HT3-R) has been implicated in the neural actions of ethanol (EtOH) and in modulation of GABA release from presynaptic terminals. In the present study, we investigated EtOH modulation of GABA release induced by 5-HT3-R activation using the mechanically isolated neuron/bouton preparation from the rat CA1 hippocampal subregion. EtOH application before and during exposure to the selective 5-HT3 receptor agonist, m-chlorophenylbiguanide (mCPBG) potentiated the mCPBG-induced increases in the peak frequency and charge transfer of spontaneous GABAergic inhibitory postsynaptic currents. Interestingly, the potentiation was maintained even after EtOH was removed from the preparation. A protein kinase A inhibitor reduced the magnitude of EtOH potentiation. Fluorescent Ca2+ imaging showed that Ca2+ transients in the presynaptic terminals increased during EtOH exposure. These findings indicate that EtOH produces long-lasting potentiation of 5-HT3-induced GABA release by modulating calcium levels, via a process involving cAMP-mediated signaling in presynaptic terminals.
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Affiliation(s)
- Sang Beom Jun
- Department of Electronic and Electrical Engineering, Ewha Womans University, Seoul, 03760, Republic of Korea; Smart Factory Multidisciplinary Program, Ewha Womans University, Seoul, 03760, Republic of Korea; Department of Brain and Cognitive Sciences, Ewha Womans University, Seoul, 03760, Republic of Korea.
| | - Stephen R Ikeda
- Section on Transmitter Signaling, Laboratory of Molecular Physiology, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD, 20892, USA.
| | - Jee Eun Sung
- Department of Communication Disorders, Ewha Womans University, Seoul, 03760, Republic of Korea.
| | - David M Lovinger
- Section on Synaptic Pharmacology, Laboratory for Integrative Neuroscience, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD, 20892, USA.
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Gibbs E, Chakrapani S. Structure, Function and Physiology of 5-Hydroxytryptamine Receptors Subtype 3. Subcell Biochem 2021; 96:373-408. [PMID: 33252737 DOI: 10.1007/978-3-030-58971-4_11] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
5-hydroxytryptamine receptor subtype 3 (5-HT3R) is a pentameric ligand-gated ion channel (pLGIC) involved in neuronal signaling. It is best known for its prominent role in gut-CNS signaling though there is growing interest in its other functions, particularly in modulating non-serotonergic synaptic activity. Recent advances in structural biology have provided mechanistic understanding of 5-HT3R function and present new opportunities for the field. This chapter gives a broad overview of 5-HT3R from a physiological and structural perspective and then discusses the specific details of ion permeation, ligand binding and allosteric coupling between these two events. Biochemical evidence is summarized and placed within a physiological context. This perspective underscores the progress that has been made as well as outstanding challenges and opportunities for future 5-HT3R research.
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Affiliation(s)
- Eric Gibbs
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, 44106-4970, USA.
| | - Sudha Chakrapani
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, 44106-4970, USA. .,Department of Neuroscience, School of Medicine, Case Western Reserve University, Cleveland, OH, 44106-4970, USA.
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9
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Biological profiling of piperazinediones for the management of anxiety. Pharmacol Biochem Behav 2019; 176:63-71. [DOI: 10.1016/j.pbb.2018.11.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Revised: 11/19/2018] [Accepted: 11/26/2018] [Indexed: 02/01/2023]
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10
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Cortes-Altamirano JL, Olmos-Hernandez A, Jaime HB, Carrillo-Mora P, Bandala C, Reyes-Long S, Alfaro-Rodríguez A. Review: 5-HT1, 5-HT2, 5-HT3 and 5-HT7 Receptors and their Role in the Modulation of Pain Response in the Central Nervous System. Curr Neuropharmacol 2018; 16:210-221. [PMID: 28901281 PMCID: PMC5883380 DOI: 10.2174/1570159x15666170911121027] [Citation(s) in RCA: 82] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Revised: 08/24/2017] [Accepted: 09/01/2017] [Indexed: 01/13/2023] Open
Abstract
BACKGROUND The aim of this review was to identify the mechanisms by which serotonin receptors involved at the central level are able to modulate the nociceptive response. Pain is a defense mechanism of the body that entails physiological, anatomical, neurochemical, and psychological changes, and is defined as an unpleasant sensory and emotional experience with potential risk of tissue damage, comprising the leading cause of appointments with Physicians worldwide. Treatment for this symptom has generated several neuropharmacological lines of research, due to the different types of pain and the various drugs employed to treat this condition. Serotonin [5- HydroxyTryptamine (5-HT)] is a neurotransmitter with seven families (5-HT1-5-HT7) and approximately 15 receptor subtypes. Serotonin modulates neuronal activity; however, this neurotransmitter is related with a number of physiological processes, such as cardiovascular function, gastric motility, renal function, etc. On the other hand, several researches reported that serotonin modulates nociceptive response through 5-HT1, 5-HT2, 5-HT3, and 5-HT7 receptors in the Central Nervous System (CNS). METHOD In this review, a search was conducted on PubMed, ProQuest, EBSCO, and the Science Citation Index for studies evaluating the effects of 5-HT1, 5-HT2, 5-HT3, and 5-HT7 receptors in the CNS on the modulation of different types of pain. CONCLUSION We concluded that 5-HT1, 5-HT2, 5-HT3, and 5-HT7 receptors in the CNS modulate the pain, but this depends on the distribution of the receptors, dose of agonists or antagonists, administration route, pain type and duration in order to inhibit, excite, or even maintain the nociceptive response.
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Affiliation(s)
- Jose Luis Cortes-Altamirano
- PhD Program in Biological and Health Sciences, Universidad Autonoma Metropolitana Iztapalapa-Xochimilco- Cuajimalpa, Mexico, Calzada del Hueso 1100, Col. Villa Quietud, Mexico, D.F. 04960, Mexico
| | - Adriana Olmos-Hernandez
- Departament of Neurosciences, Instituto Nacional de Rehabilitacion, "Luis Guillermo Ibarra Ibarra", Secretaria de Salud, Col. Arenal de Guadalupe, Mexico, D.F. 14389, Mexico
| | - Herlinda Bonilla Jaime
- Departament of Reproductive Biology, Universidad Autonoma Metropolitana Campus Iztapalapa, Mexico, D.F. 09340, Mexico
| | - Paul Carrillo-Mora
- Departament of Neurosciences, Instituto Nacional de Rehabilitacion, "Luis Guillermo Ibarra Ibarra", Secretaria de Salud, Col. Arenal de Guadalupe, Mexico, D.F. 14389, Mexico
| | - Cindy Bandala
- Departament of Neurosciences, Instituto Nacional de Rehabilitacion, "Luis Guillermo Ibarra Ibarra", Secretaria de Salud, Col. Arenal de Guadalupe, Mexico, D.F. 14389, Mexico
| | - Samuel Reyes-Long
- Departament of Neurosciences, Instituto Nacional de Rehabilitacion, "Luis Guillermo Ibarra Ibarra", Secretaria de Salud, Col. Arenal de Guadalupe, Mexico, D.F. 14389, Mexico
| | - Alfonso Alfaro-Rodríguez
- Departament of Neurosciences, Instituto Nacional de Rehabilitacion, "Luis Guillermo Ibarra Ibarra", Secretaria de Salud, Col. Arenal de Guadalupe, Mexico, D.F. 14389, Mexico
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Pandhare A, Pappu AS, Wilms H, Blanton MP, Jansen M. The antidepressant bupropion is a negative allosteric modulator of serotonin type 3A receptors. Neuropharmacology 2016; 113:89-99. [PMID: 27671323 DOI: 10.1016/j.neuropharm.2016.09.021] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Revised: 09/12/2016] [Accepted: 09/21/2016] [Indexed: 11/27/2022]
Abstract
The FDA-approved antidepressant and smoking cessation drug bupropion is known to inhibit dopamine and norepinephrine reuptake transporters, as well as nicotinic acetylcholine receptors (nAChRs) which are cation-conducting members of the Cys-loop superfamily of ion channels, and more broadly pentameric ligand-gated ion channels (pLGICs). In the present study, we examined the ability of bupropion and its primary metabolite hydroxybupropion to block the function of cation-selective serotonin type 3A receptors (5-HT3ARs), and further characterized bupropion's pharmacological effects at these receptors. Mouse 5-HT3ARs were heterologously expressed in HEK-293 cells or Xenopus laevis oocytes for equilibrium binding studies. In addition, the latter expression system was utilized for functional studies by employing two-electrode voltage-clamp recordings. Both bupropion and hydroxybupropion inhibited serotonin-gated currents from 5-HT3ARs reversibly and dose-dependently with inhibitory potencies of 87 μM and 112 μM, respectively. Notably, the measured IC50 value for hydroxybupropion is within its therapeutically-relevant concentrations. The blockade by bupropion was largely non-competitive and non-use-dependent. Unlike its modulation at cation-selective pLGICs, bupropion displayed no significant inhibition of the function of anion-selective pLGICs. In summary, our results demonstrate allosteric blockade by bupropion of the 5-HT3AR. Importantly, given the possibility that bupropion's major active metabolite may achieve clinically relevant concentrations in the brain, our novel findings delineate a not yet identified pharmacological principle underlying its antidepressant effect.
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Affiliation(s)
- Akash Pandhare
- Department of Cell Physiology and Molecular Biophysics, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX, USA; Center for Membrane Protein Research, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA.
| | - Aneesh Satya Pappu
- Department of Cell Physiology and Molecular Biophysics, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX, USA; The Clark Scholar Program, Texas Tech University, Lubbock, TX 79409, USA.
| | - Henrik Wilms
- Department of Neurology, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX, USA.
| | - Michael Paul Blanton
- Center for Membrane Protein Research, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA; Department of Pharmacology and Neuroscience, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX, USA.
| | - Michaela Jansen
- Department of Cell Physiology and Molecular Biophysics, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX, USA; Center for Membrane Protein Research, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA.
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12
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Belmer A, Klenowski PM, Patkar OL, Bartlett SE. Mapping the connectivity of serotonin transporter immunoreactive axons to excitatory and inhibitory neurochemical synapses in the mouse limbic brain. Brain Struct Funct 2016; 222:1297-1314. [PMID: 27485750 PMCID: PMC5368196 DOI: 10.1007/s00429-016-1278-x] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Accepted: 07/20/2016] [Indexed: 12/25/2022]
Abstract
Serotonin neurons arise from the brainstem raphe nuclei and send their projections throughout the brain to release 5-HT which acts as a modulator of several neuronal populations. Previous electron microscopy studies in rats have morphologically determined the distribution of 5-HT release sites (boutons) in certain brain regions and have shown that 5-HT containing boutons form synaptic contacts that are either symmetric or asymmetric. In addition, 5-HT boutons can form synaptic triads with the pre- and postsynaptic specializations of either symmetrical or asymmetrical synapses. However, due to the labor intensive processing of serial sections required by electron microscopy, little is known about the neurochemical properties or the quantitative distribution of 5-HT triads within whole brain or discrete subregions. Therefore, we used a semi-automated approach that combines immunohistochemistry and high-resolution confocal microscopy to label serotonin transporter (SERT) immunoreactive axons and reconstruct in 3D their distribution within limbic brain regions. We also used antibodies against key pre- (synaptophysin) and postsynaptic components of excitatory (PSD95) or inhibitory (gephyrin) synapses to (1) identify putative 5-HTergic boutons within SERT immunoreactive axons and, (2) quantify their close apposition to neurochemical excitatory or inhibitory synapses. We provide a 5-HTergic axon density map and have determined the ratio of synaptic triads consisting of a 5-HT bouton in close proximity to either neurochemical excitatory or inhibitory synapses within different limbic brain areas. The ability to model and map changes in 5-HTergic axonal density and the formation of triadic connectivity within whole brain regions using this rapid and quantitative approach offers new possibilities for studying neuroplastic changes in the 5-HTergic pathway.
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Affiliation(s)
- Arnauld Belmer
- Translational Research Institute, Queensland University of Technology, Brisbane, Qld 4059, Australia
| | - Paul M Klenowski
- Translational Research Institute, Queensland University of Technology, Brisbane, Qld 4059, Australia
| | - Omkar L Patkar
- Translational Research Institute, Queensland University of Technology, Brisbane, Qld 4059, Australia
| | - Selena E Bartlett
- Translational Research Institute, Queensland University of Technology, Brisbane, Qld 4059, Australia. .,Institute of Health and Biomedical Innovation (IHBI), Queensland University of Technology, Brisbane, Australia.
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13
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Kondo M. Molecular mechanisms of experience-dependent structural and functional plasticity in the brain. Anat Sci Int 2016; 92:1-17. [DOI: 10.1007/s12565-016-0358-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Accepted: 07/16/2016] [Indexed: 11/24/2022]
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14
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Contribution of Hippocampal 5-HT 3 Receptors in Hippocampal Autophagy and Extinction of Conditioned Fear Responses after a Single Prolonged Stress Exposure in Rats. Cell Mol Neurobiol 2016; 37:595-606. [PMID: 27324798 DOI: 10.1007/s10571-016-0395-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Accepted: 06/13/2016] [Indexed: 02/01/2023]
Abstract
One of the hypotheses about the pathogenesis of posttraumatic stress disorder (PTSD) is the dysfunction of serotonin (5-HT) neurotransmission. While certain 5-HT receptor subtypes are likely critical for the symptoms of PTSD, few studies have examined the role of 5-HT3 receptor in the development of PTSD, even though 5-HT3 receptor is critical for contextual fear extinction and anxiety-like behavior. Therefore, we hypothesized that stimulation of 5-HT3 receptor in the dorsal hippocampus (DH) could prevent hippocampal autophagy and the development of PTSD-like behavior in animals. To this end, we infused SR57227, selective 5-HT3 agonist, into the DH after a single prolonged stress (SPS) treatment in rats. Three weeks later, we evaluated the effects of this pharmacological treatment on anxiety-related behaviors and extinction of contextual fear memory. We also accessed hippocampal autophagy and the expression of 5-HT3A subunit, Beclin-1, LC3-I, and LC3-II in the DH. We found that SPS treatment did not alter anxiety-related behaviors but prolonged the extinction of contextual fear memory, and such a behavioral phenomenon was correlated with increased hippocampal autophagy, decreased 5-HT3A expression, and increased expression of Beclin-1 and LC3-II/LC3-I ratio in the DH. Furthermore, intraDH infusions of SR57227 dose-dependently promoted the extinction of contextual fear memory, prevented hippocampal autophagy, and decreased expression of Beclin-1 and LC3-II/LC3-I ratio in the DH. These results indicated that 5-HT3 receptor in the hippocampus may play a critical role in the pathogenesis of hippocampal autophagy, and is likely involved in the pathophysiology of PTSD.
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15
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Gupta D, Prabhakar V, Radhakrishnan M. 5HT3 receptors: Target for new antidepressant drugs. Neurosci Biobehav Rev 2016; 64:311-25. [PMID: 26976353 DOI: 10.1016/j.neubiorev.2016.03.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2015] [Revised: 02/29/2016] [Accepted: 03/01/2016] [Indexed: 12/31/2022]
Abstract
5HT3 receptors (5HT3Rs) have long been identified as a potential target for antidepressants. Several studies have reported that antagonism of 5HT3Rs produces antidepressant-like effects. However, the exact role of 5HT3Rs and the mode of antidepressant action of 5HT3R antagonists still remain a mystery. Here, we provide a comprehensive overview of 5HT3Rs: (a) regional and subcellular distribution of 5HT3Rs in discrete brain regions, (b) preclinical and clinical evidence supporting the antidepressant effect of 5HT3R antagonists, and (c) neurochemical, biological and neurocellular signaling pathways associated with the antidepressant action of 5HT3R antagonists. 5HT3Rs located on the serotonergic and other neurotransmitter interneuronal projections control their release and affect mood and emotional behavior; however, new evidence suggests that apart from modulating the neurotransmitter functions, 5HT3R antagonists have protective effects in the pathogenic events including hypothalamic-pituitary-adrenal-axis hyperactivity, brain oxidative stress and impaired neuronal plasticity, pointing to hereby unknown and novel mechanisms of their antidepressant action. Nonetheless, further investigations are warranted to establish the exact role of 5HT3Rs in depression and antidepressant action of 5HT3R antagonists.
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Affiliation(s)
- Deepali Gupta
- Department of Pharmacy, Birla Institute of Technology and Science, Pilani, Rajasthan 333031, India.
| | - Visakh Prabhakar
- Department of Pharmacy, Birla Institute of Technology and Science, Pilani, Rajasthan 333031, India.
| | - Mahesh Radhakrishnan
- Department of Pharmacy, Birla Institute of Technology and Science, Pilani, Rajasthan 333031, India.
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16
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Prager EM, Bergstrom HC, Wynn GH, Braga MFM. The basolateral amygdala γ-aminobutyric acidergic system in health and disease. J Neurosci Res 2015; 94:548-67. [PMID: 26586374 DOI: 10.1002/jnr.23690] [Citation(s) in RCA: 104] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Revised: 10/01/2015] [Accepted: 10/18/2015] [Indexed: 01/13/2023]
Abstract
The brain comprises an excitatory/inhibitory neuronal network that maintains a finely tuned balance of activity critical for normal functioning. Excitatory activity in the basolateral amygdala (BLA), a brain region that plays a central role in emotion and motivational processing, is tightly regulated by a relatively small population of γ-aminobutyric acid (GABA) inhibitory neurons. Disruption in GABAergic inhibition in the BLA can occur when there is a loss of local GABAergic interneurons, an alteration in GABAA receptor activation, or a dysregulation of mechanisms that modulate BLA GABAergic inhibition. Disruptions in GABAergic control of the BLA emerge during development, in aging populations, or after trauma, ultimately resulting in hyperexcitability. BLA hyperexcitability manifests behaviorally as an increase in anxiety, emotional dysregulation, or development of seizure activity. This Review discusses the anatomy, development, and physiology of the GABAergic system in the BLA and circuits that modulate GABAergic inhibition, including the dopaminergic, serotonergic, noradrenergic, and cholinergic systems. We highlight how alterations in various neurotransmitter receptors, including the acid-sensing ion channel 1a, cannabinoid receptor 1, and glutamate receptor subtypes, expressed on BLA interneurons, modulate GABAergic transmission and how defects of these systems affect inhibitory tonus within the BLA. Finally, we discuss alterations in the BLA GABAergic system in neurodevelopmental (autism/fragile X syndrome) and neurodegenerative (Alzheimer's disease) diseases and after the development of epilepsy, anxiety, and traumatic brain injury. A more complete understanding of the intrinsic excitatory/inhibitory circuit balance of the amygdala and how imbalances in inhibitory control contribute to excessive BLA excitability will guide the development of novel therapeutic approaches in neuropsychiatric diseases.
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Affiliation(s)
- Eric M Prager
- Department of Anatomy, Physiology, and Genetics, F. Edward Hébert School of Medicine, Uniformed Services, University of the Health Sciences, Bethesda, Maryland
| | | | - Gary H Wynn
- Center for the Study of Traumatic Stress, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland.,Department of Psychiatry, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland.,Program in Neuroscience, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland
| | - Maria F M Braga
- Department of Anatomy, Physiology, and Genetics, F. Edward Hébert School of Medicine, Uniformed Services, University of the Health Sciences, Bethesda, Maryland.,Center for the Study of Traumatic Stress, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland.,Department of Psychiatry, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland.,Program in Neuroscience, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland
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17
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Gupta D, Thangaraj D, Radhakrishnan M. A novel 5HT3 antagonist 4i (N-(3-chloro-2-methylphenyl)quinoxalin-2-carboxamide) prevents diabetes-induced depressive phenotypes in mice: Modulation of serotonergic system. Behav Brain Res 2015; 297:41-50. [PMID: 26454237 DOI: 10.1016/j.bbr.2015.10.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Revised: 10/01/2015] [Accepted: 10/03/2015] [Indexed: 11/16/2022]
Abstract
Despite the presence of a multitudinous pharmacotherapy, diabetes-induced depressive disorder remains undertreated. Evidence suggests that brain serotonergic deficits are associated with depressive-like behavior in diabetes and that 5HT3 receptor (5HT3R) antagonists have serotonergic facilitatory effects. This study examined the effects of a novel 5HT3R antagonist, 4i (N-(3-chloro-2-methylphenyl)quinoxalin-2-carboxamide), in diabetes-induced depressive phenotypes. Experimentally, (1) to evaluate the effects of 4i, mice with 8-weeks of diabetes (induced by streptozotocin, 200mg/kg, i.p.) were treated with vehicle, 4i (0.5 and 1mg/kg/day, i.p.), fluoxetine (10mg/kg/day, i.p.) for 4-weeks and subjected to neurobehavioral assays, followed by biochemical estimation of serotonin levels in midbrain, prefrontal-cortex and cerebellum. (2) To evaluate the role of 5HT3R in the postulated effect of 4i, diabetic mice were given 4i (1mg/kg/day, i.p.) after 1h of 1-(m-chlorophenyl)-biguanide (mCPBG, a 5HT3R agonist, 10mg/kg/day, i.p.) treatment and subjected to the same protocol. The results showed that diabetic mice exhibited a significant behavioral deficit, including depression-like behavior in forced swim test, anxiety-like in open field test and sociability deficits in social interaction test, along with a significant decrease in serotonin level in these brain regions. 4i (1mg/kg), similar to fluoxetine, prevented these behavioral abnormalities and normalized brain serotonin levels. 4i (0.5mg/kg) ameliorated only diabetes-induced depressive-like behavior and serotonin deficits, but not anxiety-like effects. mCPBG blunted 4i-mediated behavioral response and increase in brain serotonin levels. Altogether, this study suggests that 4i prevents diabetes-induced depressive phenotypes in mice, which may involve antagonism of 5HT3Rs and increase in serotonin levels in discrete brain regions.
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Affiliation(s)
- Deepali Gupta
- Department of Pharmacy, Birla Institute of Technology & Science, Pilani, Rajasthan 333031, India.
| | - Devadoss Thangaraj
- KVSR Siddhartha College of Pharmaceutical Sciences, Vijaywada, Andhra Pradesh 520001, India
| | - Mahesh Radhakrishnan
- Department of Pharmacy, Birla Institute of Technology and Science, Pilani, Rajasthan 333031, India
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18
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Dale E, Zhang H, Leiser SC, Xiao Y, Lu D, Yang CR, Plath N, Sanchez C. Vortioxetine disinhibits pyramidal cell function and enhances synaptic plasticity in the rat hippocampus. J Psychopharmacol 2014; 28:891-902. [PMID: 25122043 PMCID: PMC4230848 DOI: 10.1177/0269881114543719] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Vortioxetine, a novel antidepressant with multimodal action, is a serotonin (5-HT)3, 5-HT7 and 5-HT1D receptor antagonist, a 5-HT1B receptor partial agonist, a 5-HT1A receptor agonist and a 5-HT transporter (SERT) inhibitor. Vortioxetine has been shown to improve cognitive performance in several preclinical rat models and in patients with major depressive disorder. Here we investigated the mechanistic basis for these effects by studying the effect of vortioxetine on synaptic transmission, long-term potentiation (LTP), a cellular correlate of learning and memory, and theta oscillations in the rat hippocampus and frontal cortex. Vortioxetine was found to prevent the 5-HT-induced increase in inhibitory post-synaptic potentials recorded from CA1 pyramidal cells, most likely by 5-HT3 receptor antagonism. Vortioxetine also enhanced LTP in the CA1 region of the hippocampus. Finally, vortioxetine increased fronto-cortical theta power during active wake in whole animal electroencephalographic recordings. In comparison, the selective SERT inhibitor escitalopram showed no effect on any of these measures. Taken together, our results indicate that vortioxetine can increase pyramidal cell output, which leads to enhanced synaptic plasticity in the hippocampus. Given the central role of the hippocampus in cognition, these findings may provide a cellular correlate to the observed preclinical and clinical cognition-enhancing effects of vortioxetine.
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Affiliation(s)
| | | | | | - Yixin Xiao
- Shanghai Chempartner Co. Ltd., Shanghai, China
| | - Dunguo Lu
- Shanghai Chempartner Co. Ltd., Shanghai, China
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Kondo M, Nakamura Y, Ishida Y, Yamada T, Shimada S. The 5-HT3A receptor is essential for fear extinction. Learn Mem 2013; 21:1-4. [PMID: 24344177 PMCID: PMC3867712 DOI: 10.1101/lm.032193.113] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The 5-HT3 receptor, the only ionotropic 5-HT receptor, is expressed in limbic regions, including the hippocampus, amygdala, and cortex. However, it is not known whether it has a role in fear memory processes. Analysis of 5-HT3A receptor knockout mice in fear conditioning paradigms revealed that the 5-HT3A receptor is not required for the acquisition or retention of fear memory but is essential for the extinction of contextual and tone-cued fear. Our data suggest that the 5-HT3A receptor could be a key molecule regulating fear memory processes and a potential therapeutic target for fear disorders.
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Affiliation(s)
- Makoto Kondo
- Department of Neuroscience and Cell Biology, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan
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20
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Lack of interaction of endocannabinoids and 5-HT3 neurotransmission in associative fear circuits of the amygdala: Evidence from electrophysiological and behavioural experiments. Brain Res 2013; 1527:47-56. [DOI: 10.1016/j.brainres.2013.06.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Revised: 06/06/2013] [Accepted: 06/08/2013] [Indexed: 01/09/2023]
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21
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Asan E, Steinke M, Lesch KP. Serotonergic innervation of the amygdala: targets, receptors, and implications for stress and anxiety. Histochem Cell Biol 2013; 139:785-813. [DOI: 10.1007/s00418-013-1081-1] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/02/2013] [Indexed: 01/09/2023]
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22
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Fukuda T, Hirai Y, Maezawa H, Kitagawa Y, Funahashi M. Electrophysiologically identified presynaptic mechanisms underlying amylinergic modulation of area postrema neuronal excitability in rat brain slices. Brain Res 2013; 1494:9-16. [DOI: 10.1016/j.brainres.2012.11.051] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2012] [Revised: 11/28/2012] [Accepted: 11/29/2012] [Indexed: 11/30/2022]
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23
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Masalov IS, Tsvetkov EA, Lokshina EI, Vesselkin NP. Effect of antagonists of serotonin receptors on modulation with serotonin of synaptic activity of projectional neurons of rat amygdala dorsolateral nucleus. J EVOL BIOCHEM PHYS+ 2013. [DOI: 10.1134/s0022093012050064] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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24
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Akhmadeev AV, Kalimullina LB. Sex Steroids and Monoamines in the System of Neuroendocrine Regulation of the Functions of the Amygdaloid Complex of the Brain. ACTA ACUST UNITED AC 2013. [DOI: 10.1007/s11055-012-9702-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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25
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The effects of volatile anesthetics on synaptic and extrasynaptic GABA-induced neurotransmission. Brain Res Bull 2012; 93:69-79. [PMID: 22925739 DOI: 10.1016/j.brainresbull.2012.08.001] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2012] [Revised: 07/17/2012] [Accepted: 08/01/2012] [Indexed: 02/02/2023]
Abstract
Examination of volatile anesthetic actions at single synapses provides more direct information by reducing interference by surrounding tissue and extrasynaptic modulation. We examined how volatile anesthetics modulate GABA release by measuring spontaneous or miniature GABA-induced inhibitory postsynaptic currents (mIPSCs, sIPSCs) or by measuring action potential-evoked IPSCs (eIPSCs) at individual synapses. Halothane increased both the amplitude and frequency of sIPSCs. Isoflurane and enflurane increased mIPSC frequency while sevoflurane had no effect. These anesthetics did not alter mIPSC amplitudes. Halothane increased the amplitude of eIPSCs, with a decrease in failure rate (Rf) and paired-pulse ratio. In contrast, isoflurane and enflurane decreased the eIPSC amplitude and increased Rf, while sevoflurane decreased the eIPSC amplitude without affecting Rf. Volatile anesthetics did not change kinetics except for sevoflurane, suggesting that presynaptic mechanisms dominate changes in neurotransmission. Each anesthetic showed somewhat different GABA-induced response and these results suggest that GABA-induced synaptic transmission cannot have a uniformly common site of action as suggested for volatile anesthetics. In contrast, all volatile anesthetics concentration-dependently enhanced the GABA-induced extrasynaptic currents. Extrasynaptic receptors containing α4 and α5 subunits are reported to have high sensitivities to volatile anesthetics. Also, inhibition of GABA uptake by volatile anesthetics results in higher extracellular GABA concentration, which may lead to prolonged activation of extrasynaptic GABAA receptors. The extrasynaptic GABA-induced receptors may be major site of volatile anesthetic-induced neurotransmission. This article is part of a Special Issue entitled 'Extrasynaptic ionotropic receptors'.
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26
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Kawamoto EM, Vivar C, Camandola S. Physiology and pathology of calcium signaling in the brain. Front Pharmacol 2012; 3:61. [PMID: 22518105 PMCID: PMC3325487 DOI: 10.3389/fphar.2012.00061] [Citation(s) in RCA: 130] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2012] [Accepted: 03/26/2012] [Indexed: 12/31/2022] Open
Abstract
Calcium (Ca(2+)) plays fundamental and diversified roles in neuronal plasticity. As second messenger of many signaling pathways, Ca(2+) as been shown to regulate neuronal gene expression, energy production, membrane excitability, synaptogenesis, synaptic transmission, and other processes underlying learning and memory and cell survival. The flexibility of Ca(2+) signaling is achieved by modifying cytosolic Ca(2+) concentrations via regulated opening of plasma membrane and subcellular Ca(2+) sensitive channels. The spatiotemporal patterns of intracellular Ca(2+) signals, and the ultimate cellular biological outcome, are also dependent upon termination mechanism, such as Ca(2+) buffering, extracellular extrusion, and intra-organelle sequestration. Because of the central role played by Ca(2+) in neuronal physiology, it is not surprising that even modest impairments of Ca(2+) homeostasis result in profound functional alterations. Despite their heterogeneous etiology neurodegenerative disorders, as well as the healthy aging process, are all characterized by disruption of Ca(2+) homeostasis and signaling. In this review we provide an overview of the main types of neuronal Ca(2+) channels and their role in neuronal plasticity. We will also discuss the participation of Ca(2+) signaling in neuronal aging and degeneration.
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Affiliation(s)
- Elisa Mitiko Kawamoto
- Laboratory of Neurosciences, National Institute on Aging, Intramural Research ProgramBaltimore, MD, USA
| | - Carmen Vivar
- Laboratory of Neurosciences, National Institute on Aging, Intramural Research ProgramBaltimore, MD, USA
| | - Simonetta Camandola
- Laboratory of Neurosciences, National Institute on Aging, Intramural Research ProgramBaltimore, MD, USA
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5-HT(3A) receptor-bearing white matter interstitial GABAergic interneurons are functionally integrated into cortical and subcortical networks. J Neurosci 2012; 31:16844-54. [PMID: 22090510 DOI: 10.1523/jneurosci.0310-11.2011] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
In addition to axons and surrounding glial cells, the corpus callosum also contains interstitial neurons that constitute a heterogeneous cell population. There is growing anatomical evidence that white matter interstitial cells (WMICs) comprise GABAergic interneurons, but so far there is little functional evidence regarding their connectivity. The scarcity of these cells has hampered electrophysiological studies. We overcame this hindrance by taking recourse to transgenic mice in which distinct WMICs expressed enhanced green fluorescence protein (EGFP). The neuronal phenotype of the EGFP-labeled WMICs was confirmed by their NeuN positivity. The GABAergic phenotype could be established based on vasoactive intestinal peptide and calretinin expression and was further supported by a firing pattern typical for interneurons. Axons and dendrites of many EGFP-labeled WMICs extended to the cortex, hippocampus, and striatum. Patch-clamp recordings in acute slices showed that they receive excitatory and inhibitory input from cortical and subcortical structures. Moreover, paired recordings revealed that EGFP-labeled WMICs inhibit principal cells of the adjacent cortex, thus providing unequivocal functional evidence for their GABAergic phenotype and demonstrating that they are functionally integrated into neuronal networks.
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28
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Kilpatrick LA, Labus JS, Coveleskie K, Hammer C, Rappold G, Tillisch K, Bueller JA, Suyenobu B, Jarcho JM, McRoberts JA, Niesler B, Mayer EA. The HTR3A polymorphism c. -42C>T is associated with amygdala responsiveness in patients with irritable bowel syndrome. Gastroenterology 2011; 140:1943-51. [PMID: 21420406 PMCID: PMC3757951 DOI: 10.1053/j.gastro.2011.03.011] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/10/2010] [Revised: 02/02/2011] [Accepted: 03/07/2011] [Indexed: 12/19/2022]
Abstract
BACKGROUND & AIMS 5-Hydroxytryptamine (5-HT)3 receptor (5-HT3R) antagonists are effective in treating patients with irritable bowel syndrome (IBS) and have anxiolytic effects. Their therapeutic effects are related, in part, to reducing amygdala engagement during expected visceral pain. A single nucleotide polymorphism in HTR3A, c.-42C>T;(C178T; rs1062613), is associated with altered reactivity of the amygdala during emotional face processing in healthy subjects (controls). We evaluated the influence of this single nucleotide polymorphism on amygdala reactivity to emotional faces and nonemotional stimuli in female patients with IBS and controls. METHODS We measured brain responses during an affect-matching paradigm in 54 women (26 with IBS, 29 controls) using functional magnetic resonance imaging. We examined associations between HTR3A c.-42C>T genotype (C/C vs T carrier) and responses in amygdala and other regions of brain that expressed high levels of 5-HT3R. RESULTS The C/C genotype was associated with greater anxiety symptoms in patients with IBS and controls and increased activation of the amygdala under emotional and nonemotional conditions. Among patients with IBS, C/C genotype was associated with greater symptom ratings. A subset of IBS patients with the C/C genotype had increased amygdala responses to nonemotional stimuli, compared with other subjects with C/C genotype. CONCLUSIONS Regardless of diagnosis, the C/C genotype of the c.-42C>T polymorphism in HTR3A, compared with T carrier status, is associated with increased anxiety and amygdala responsiveness during emotional and nonemotional tasks. This polymorphism was associated with severity of IBS symptoms. Although this genotype is not sufficient for diagnosis of IBS, it is associated with severity of symptoms.
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Affiliation(s)
- LA Kilpatrick
- Center for Neurobiology of Stress, Ahmanson-Lovelace Brain Mapping Center, UCLA, Department of Medicine, Ahmanson-Lovelace Brain Mapping Center, UCLA
| | - JS Labus
- Center for Neurobiology of Stress, Ahmanson-Lovelace Brain Mapping Center, UCLA, Department of Psychiatry & Biobehavioral Sciences, Ahmanson-Lovelace Brain Mapping Center, UCLA, Brain Research Institute, David Geffen School of Medicine, UCLA
| | - K Coveleskie
- Center for Neurobiology of Stress, Ahmanson-Lovelace Brain Mapping Center, UCLA
| | - C Hammer
- Department of Human Molecular Genetics, University of Heidelberg, Germany
| | - G Rappold
- Department of Human Molecular Genetics, University of Heidelberg, Germany
| | - K Tillisch
- Center for Neurobiology of Stress, Ahmanson-Lovelace Brain Mapping Center, UCLA, Department of Medicine, Ahmanson-Lovelace Brain Mapping Center, UCLA
| | - JA Bueller
- Center for Neurobiology of Stress, Ahmanson-Lovelace Brain Mapping Center, UCLA, Department of Medicine, Ahmanson-Lovelace Brain Mapping Center, UCLA
| | - B Suyenobu
- Center for Neurobiology of Stress, Ahmanson-Lovelace Brain Mapping Center, UCLA, Department of Medicine, Ahmanson-Lovelace Brain Mapping Center, UCLA
| | - JM Jarcho
- Center for Neurobiology of Stress, Ahmanson-Lovelace Brain Mapping Center, UCLA, Department of Medicine, Ahmanson-Lovelace Brain Mapping Center, UCLA
| | - JA McRoberts
- Center for Neurobiology of Stress, Ahmanson-Lovelace Brain Mapping Center, UCLA, Department of Medicine, Ahmanson-Lovelace Brain Mapping Center, UCLA
| | - B Niesler
- Department of Human Molecular Genetics, University of Heidelberg, Germany
| | - EA Mayer
- Center for Neurobiology of Stress, Ahmanson-Lovelace Brain Mapping Center, UCLA, Department of Medicine, Ahmanson-Lovelace Brain Mapping Center, UCLA, Department of Psychiatry & Biobehavioral Sciences, Ahmanson-Lovelace Brain Mapping Center, UCLA, Brain Research Institute, David Geffen School of Medicine, UCLA
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Jun SB, Cuzon Carlson V, Ikeda S, Lovinger D. Vibrodissociation of neurons from rodent brain slices to study synaptic transmission and image presynaptic terminals. J Vis Exp 2011:2752. [PMID: 21654624 PMCID: PMC3197124 DOI: 10.3791/2752] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Mechanical dissociation of neurons from the central nervous system has the advantage that presynaptic boutons remain attached to the isolated neuron of interest. This allows for examination of synaptic transmission under conditions where the extracellular and postsynaptic intracellular environments can be well controlled. A vibration-based technique without the use of proteases, known as vibrodissociation, is the most popular technique for mechanical isolation. A micropipette, with the tip fire-polished to the shape of a small ball, is placed into a brain slice made from a P1-P21 rodent. The micropipette is vibrated parallel to the slice surface and lowered through the slice thickness resulting in the liberation of isolated neurons. The isolated neurons are ready for study within a few minutes of vibrodissociation. This technique has advantages over the use of primary neuronal cultures, brain slices and enzymatically isolated neurons including: rapid production of viable, relatively mature neurons suitable for electrophysiological and imaging studies; superior control of the extracellular environment free from the influence of neighboring cells; suitability for well-controlled pharmacological experiments using rapid drug application and total cell superfusion; and improved space-clamp in whole-cell recordings relative to neurons in slice or cell culture preparations. This preparation can be used to examine synaptic physiology, pharmacology, modulation and plasticity. Real-time imaging of both pre- and postsynaptic elements in the living cells and boutons is also possible using vibrodissociated neurons. Characterization of the molecular constituents of pre- and postsynaptic elements can also be achieved with immunological and imaging-based approaches.
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Affiliation(s)
- Sang Beom Jun
- Section on Synaptic Pharmacology/Laboratory for Integrative Neuroscience, National Institutes of Health/National Institute on Alcohol Abuse and Alcoholism
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Blockade of 5-HT3 receptors at septal area increase blood pressure in unanaesthetized rats. Auton Neurosci 2011; 159:51-61. [DOI: 10.1016/j.autneu.2010.07.028] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2010] [Revised: 07/10/2010] [Accepted: 07/30/2010] [Indexed: 11/20/2022]
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Rajkumar R, Mahesh R. The auspicious role of the 5-HT3 receptor in depression: a probable neuronal target? J Psychopharmacol 2010; 24:455-69. [PMID: 20123937 DOI: 10.1177/0269881109348161] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The serotonergic mechanisms have been successfully utilized by the majority of antidepressant drug discovery programmes, while the search for newer targets remains persistent. The present review focused on the serotonin type-3 receptor, the only ion channel subtype in the serotonin family. Behavioural, neurochemical, electrophysiological and molecular analyses, including the results from our laboratory, provided substantial evidence that rationalizes the correlation between serotonin type-3 receptor modulation and rodent depressive-like behaviour. Nevertheless, the reports on polymorphism of serotonin type-3 receptor genes and data from clinical studies (on serotonin type-3 receptor antagonists) were insufficient to corroborate the involvement of this receptor in the neurobiology of depression. The preclinical and clinical studies that have contradicted the antidepressant-like effects of serotonin type-3 receptor antagonists and the reasons underlying such disagreement were discussed. Finally, this critical review commended the serotonin type-3 receptor as a candidate neuronal antidepressant drug target.
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Feinberg-Zadek PL, Davies PA. Ethanol stabilizes the open state of single 5-hydroxytryptamine(3A)(QDA) receptors. J Pharmacol Exp Ther 2010; 333:896-902. [PMID: 20200118 DOI: 10.1124/jpet.109.164863] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Ethanol enhancement of 5-hydroxytryptamine (5-HT)(3A) receptor-mediated responses may have important consequences in the intoxicating and addictive properties of ethanol. Although the exact mechanism is unknown, ethanol-mediated enhancement of 5-HT(3) receptor current has been proposed to occur due to stabilization of the open-channel state. It has not been possible to directly measure the open state of the channel due to the extremely low single-channel conductance of 5-HT(3A) channels. Recently, three arginine residues within the large intracellular loop of the 5-HT(3A) subunit were substituted by their equivalent residues (glutamine, aspartate, and alanine) of the 5-HT(3B) subunit to produce a 5-HT(3A)(QDA) subunit that forms functional homomeric channels exhibiting a measurable single-channel conductance. Using whole-cell rapid-agonist application techniques and the cell-attached single-channel recording configuration, we examined human 5-HT(3A)(QDA) receptors expressed in human embryonic kidney 293 cells. The agonist sensitivity, macroscopic kinetics, and modulation by ethanol were similar between mutant and wild-type channels, suggesting the substitutions had not altered these channel structure-function properties. The open time histogram for single-channel events mediated by 5-HT(3A)(QDA) receptors in the presence of maximal 5-HT was best fit by three exponentials, but in the presence of ethanol a fourth open state was evident. In summary, the QDA substitution greatly enhanced single-channel conductance with little effect on 5-HT(3A) channel's kinetic properties and ethanol enhances agonist action on 5-HT(3A) receptors by inducing a new, long-lived open-channel state. Furthermore, the 5-HT(3A)(QDA) receptor appears to be suitable for pharmacological studies of 5-HT(3A) receptor modulation at a single-channel level.
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Affiliation(s)
- Paula L Feinberg-Zadek
- Department of Anesthesia and Critical Care, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA
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Electrophysiology of Serotonin Receptors. ACTA ACUST UNITED AC 2010. [DOI: 10.1016/s1569-7339(10)70077-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Rammes G, Hosp C, Eisensamer B, Tanasic S, Nothdurfter C, Zieglgänsberger W, Rupprecht R. Identification of a domain which affects kinetics and antagonistic potency of clozapine at 5-HT3 receptors. PLoS One 2009; 4:e6715. [PMID: 19696922 PMCID: PMC2725292 DOI: 10.1371/journal.pone.0006715] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2009] [Accepted: 07/17/2009] [Indexed: 11/18/2022] Open
Abstract
The widely used atypical antipsychotic clozapine is a potent competitive antagonist at 5-HT3 receptors which may contribute to its unique psychopharmacological profile. Clozapine binds to 5-HT3 receptors of various species. However, the structural requirements of the respective binding site for clozapine remain to be determined. Differences in the primary sequences within the 5-HT3A receptor gene in schizophrenic patients may result in an alteration of the antipsychotic potency and/or the side effect profile of clozapine. To determine these structural requirements we constructed chimeras with different 5-HT3A receptor sequences of murine and human origin and expressed these mutants in human embryonic kidney (HEK) 293 cells. Clozapine antagonises recombinant mouse 5-HT3A receptors with higher potency compared to recombinant human 5-HT3A receptors. 5-HT activation curves and clozapine inhibition curves yielded the parameters EC50 and IC50 for all receptors tested in the range of 0.6–2.7 µM and 1.5–83.3 nM, respectively. The use of the Cheng-Prusoff equation to calculate the dissociation constant Kb values for clozapine revealed that an extracellular sequence (length 86 aa) close to the transmembrane domain M1 strongly determines the binding affinity of clozapine. Kb values of clozapine were significantly lower (0.3–1.1 nM) for receptors containing the murine sequence and higher when compared with receptors containing the respective human sequence (5.8–13.4 nM). Thus, individual differences in the primary sequence of 5-HT3 receptors may be crucial for the antipsychotic potency and/or the side effect profile of clozapine.
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Fukushima T, Ohtsubo T, Tsuda M, Yanagawa Y, Hori Y. Facilitatory actions of serotonin type 3 receptors on GABAergic inhibitory synaptic transmission in the spinal superficial dorsal horn. J Neurophysiol 2009; 102:1459-71. [PMID: 19369358 DOI: 10.1152/jn.91160.2008] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Analgesic effects of serotonin (5-hydroxytryptamine [5-HT]) type 3 (5-HT3) receptors may involve the release of gamma-aminobutyric acid (GABA) in the spinal dorsal horn. However, the precise synaptic mechanisms for 5-HT3 receptor-mediated spinal analgesia are not clear. In this study, we investigated whether GABAergic neurons in the superficial dorsal horn (SDH) express functional 5-HT3 receptors and how these 5-HT3 receptors affect GABAergic inhibitory synaptic transmission in the SDH, by using slice preparations from adult glutamate decarboxylase 67-green fluorescent protein (GAD67-GFP) knock-in mice. Tight-seal whole cell recordings from GFP-positive and -negative neurons showed that 5-HT3 receptor-specific agonist 2-methyl-serotonin (2-Me-5-HT) induced inward currents in a substantial population of both GFP-positive and -negative neurons. Additionally, we confirmed expression of 5-HT3 receptors in both types of neurons by single-cell reverse transcription-polymerase chain reaction (RT-PCR) analysis. Further, GABAA receptor-mediated inhibitory postsynaptic currents (IPSCs)-both those evoked by electrical stimulation and those occurring spontaneously in tetrodotoxin (i.e., miniature IPSCs [mIPSCs])-were recorded from GFP-negative neurons. 2-Me-5-HT increased the amplitude of the evoked IPSCs and the frequency of mIPSCs. The amplitude of mIPSCs was not affected by 2-Me-5-HT, suggesting that 5-HT augments GABAergic synaptic transmission via presynaptic mechanisms. The present observations indicate that 5-HT3 receptors are expressed on both somadendritic regions and presynaptic terminals of GABAergic neurons and regulate GABAA receptor-mediated inhibitory synaptic transmission in the SDH. Taken together, these results provide clues for the underlying mechanisms of the antinociceptive actions of 5-HT3 receptors in the spinal dorsal horn.
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Affiliation(s)
- Teruyuki Fukushima
- Department of Physiology and Biological Information, Dokkyo Medical University School of Medicine, Kitakobayashi 880, Mibu, Tochigi 321-0293, Japan
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Bohorquez A, Hurley LM. Activation of serotonin 3 receptors changes in vivo auditory responses in the mouse inferior colliculus. Hear Res 2009; 251:29-38. [PMID: 19236912 DOI: 10.1016/j.heares.2009.02.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/23/2008] [Revised: 01/20/2009] [Accepted: 02/12/2009] [Indexed: 12/01/2022]
Abstract
Metabotropic serotonin receptors such as 5-HT1A and 5-HT1B receptors shape the level, selectivity, and timing of auditory responses in the inferior colliculus (IC). Less is known about the effects of ionotropic 5-HT3 receptors, which are cation channels that depolarize neurons. In the present study, the influence of the 5-HT3 receptor on auditory responses in vivo was explored by locally iontophoresing a 5-HT3 receptor agonist and antagonists onto single neurons recorded extracellularly in mice. Three main findings emerge from these experiments. First, activation of the 5-HT3 receptor can either facilitate or suppress auditory responses, but response suppressions are not consistent with 5-HT3 effects on presynaptic GABAergic neurons. Both response facilitations and suppressions are less pronounced in neurons with high precision in response latency, suggesting functional differences in the role of receptor activation for different classes of neuron. Finally, the effects of 5-HT3 activation vary across repetition rate within a subset of single neurons, suggesting that the influence of receptor activation sometimes varies with the level of activity. These findings contribute to the view of the 5-HT3 receptor as an important component of the serotonergic infrastructure in the IC, with effects that are complex and neuron-selective.
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Affiliation(s)
- Alexander Bohorquez
- Department of Biology, Center for the Integrative Study of Animal Behavior, Program in Neuroscience, Indiana University, 1001 E. Third St., Bloomington, IN 47405, USA
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Barnes NM, Hales TG, Lummis SC, Peters JA. The 5-HT3 receptor--the relationship between structure and function. Neuropharmacology 2009; 56:273-84. [PMID: 18761359 PMCID: PMC6485434 DOI: 10.1016/j.neuropharm.2008.08.003] [Citation(s) in RCA: 174] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2008] [Revised: 07/31/2008] [Accepted: 08/01/2008] [Indexed: 12/15/2022]
Abstract
The 5-hydroxytryptamine type-3 (5-HT3) receptor is a cation-selective ion channel of the Cys-loop superfamily. 5-HT3 receptor activation in the central and peripheral nervous systems evokes neuronal excitation and neurotransmitter release. Here, we review the relationship between the structure and the function of the 5-HT3 receptor. 5-HT3A and 5-HT3B subunits are well established components of 5-HT3 receptors but additional HTR3C, HTR3D and HTR3E genes expand the potential for molecular diversity within the family. Studies upon the relationship between subunit structure and the ionic selectivity and single channel conductances of 5-HT3 receptors have identified a novel domain (the intracellular MA-stretch) that contributes to ion permeation and selectivity. Conventional and unnatural amino acid mutagenesis of the extracellular domain of the receptor has revealed residues, within the principle (A-C) and complementary (D-F) loops, which are crucial to ligand binding. An area requiring much further investigation is the subunit composition of 5-HT3 receptors that are endogenous to neurones, and their regional expression within the central nervous system. We conclude by describing recent studies that have identified numerous HTR3A and HTR3B gene polymorphisms that impact upon 5-HT3 receptor function, or expression, and consider their relevance to (patho)physiology.
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Affiliation(s)
- Nicholas M. Barnes
- Cellular and Molecular Neuropharmacology Research Group, Department of Pharmacology, Division of Neuroscience, The Medical School, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Tim G. Hales
- Department of Pharmacology and Physiology, The George Washington University, Washington, DC 20037, USA
| | - Sarah C.R. Lummis
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QW, UK
| | - John A. Peters
- Neurosciences Institute, Division of Pathology and Neuroscience, Ninewells Hospital and Medical School, The University of Dundee, Dundee DD1 9SY, UK
- Corresponding author. Tel.: +44 01382 660111x33117; fax: +44 01382 667120. E-mail address: (J.A. Peters)
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Stress impairs 5-HT2A receptor-mediated serotonergic facilitation of GABA release in juvenile rat basolateral amygdala. Neuropsychopharmacology 2009; 34:410-23. [PMID: 18536707 DOI: 10.1038/npp.2008.71] [Citation(s) in RCA: 107] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The occurrence of stress and anxiety disorders has been closely associated with alterations of the amygdala GABAergic system. In these disorders, dysregulation of the serotonergic system, a very important modulator of the amygdala GABAergic system, is also well recognized. The present study, utilizing a learned helplessness stress rat model, was designed to determine whether stress is capable of altering serotonergic modulation of the amygdala GABAergic system. In control rats, administration of 5-HT or alpha-methyl-5-HT, a 5-HT(2) receptor agonist, to basolateral amygdala (BLA) slices dramatically enhanced frequency and amplitude of spontaneous inhibitory postsynaptic currents (sIPSCs). This effect was blocked by selective 5-HT(2A) receptor antagonists while a selective 5-HT(2B) receptor agonist and a selective 5-HT(2C) receptor agonist were without effect on sIPSCs. Double immunofluorescence labeling demonstrated that the 5-HT(2A) receptor is primarily localized to parvalbumin-containing BLA interneurons. Thus, serotonin primarily acts via 5-HT(2A) receptors to facilitate BLA GABAergic inhibition. In stressed rats, the 5-HT(2A) receptor-mediated facilitative actions were severely impaired. Quantitative RT-PCR and western blot analysis showed that the impairment of 5-HT(2A) receptor signaling primarily resulted from receptor downregulation. The stress-induced effect appeared to be specific to 5-HT(2A) receptors because stress had no significant impact on other serotonin receptors, as well as histamine H(3) receptor and alpha(2) adrenoceptor signaling in the BLA. This severe impairment of 5-HT(2A) receptor-mediated facilitation of BLA GABAergic inhibition might result in an amygdala circuitry with hyperexcitability, and a lower threshold of activation, and thus be an important mechanism underlying the emergence of stress-associated psychiatric symptoms.
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Seidel MF, Fiebich BL, Ulrich-Merzenich G, Candelario-Jalil E, Koch FW, Vetter H. Serotonin mediates PGE2 overexpression through 5-HT2A and 5-HT3 receptor subtypes in serum-free tissue culture of macrophage-like synovial cells. Rheumatol Int 2008; 28:1017-22. [PMID: 18368410 DOI: 10.1007/s00296-008-0564-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2007] [Accepted: 03/08/2008] [Indexed: 10/22/2022]
Abstract
Serotonin antagonists show impressive analgesic efficacy in rheumatoid arthritis, osteoarthritis (OA) or fibromyalgia; however, this effect is not well understood. We examined the mechanism of serotonin-induced inflammation and its antagonists in OA. Serotonin receptor subtypes and COX-2 were analysed by RT-PCR from synovial tissue. Serum-free cultures were stimulated with 10 muM serotonin and/or the antagonists ketanserin (5-HT(2A)), tropisetron (5-HT(3)) and parecoxib (COX-2). Prostaglandin E(2) (PGE(2)), tumour necrosis factor alpha (TNF-alpha), interleukin 1beta (IL-1beta) and leukotriene B4 (LTB4) were measured by an immunoassay in the supernatants. RT-PCR results showed mRNA for 5-HT(2A) and 5-HT(3) receptors, and COX-2. PGE(2) in the supernatants increased by 261.2% +/- 56.7 (mean +/- SEM; P = 0.007) in response to serotonin. TNF-alpha, IL-1beta and LTB4 levels did not change. Ketanserin, tropisetron and parecoxib suppressed PGE(2). The serotonin-induced PGE(2) overexpression appeared thus to be mediated by 5-HT(2A) and 5-HT(3) receptors. This activation might involve COX-2. The findings may explain the potent benefit of 5-HT(3) antagonists.
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Kim KJ, Cho HS, Choi SJ, Jeun SH, Kim SY, Sung KW. Direct effects of riluzole on 5-hydroxytryptamine (5-HT)3 receptor-activated ion currents in NCB-20 neuroblastoma cells. J Pharmacol Sci 2008; 107:57-65. [PMID: 18460823 DOI: 10.1254/jphs.fp0072095] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Abstract
The pharmacological action of riluzole, a drug that has been approved as a neuroprotective agent for the treatment of amyotrophic lateral sclerosis, has not yet been established. We examined the effects of riluzole on 5-hydroxytryptamine (5-HT)3) receptors in NCB-20 neuroblastoma cells using the whole-cell voltage clamp technique combined with a fast drug application method. Co-application of riluzole (1 - 300 microM, 5 s) produced a dose-dependent reduction in peak amplitudes and in the rise slope of the currents induced by 2 microM 5-HT. In addition, 5-HT3-mediated currents evoked by dopamine, a partial 5-HT3-receptor agonist, were inhibited by riluzole co-application. These inhibitory effects were clearly shown at low concentrations of 5-HT. The decay time constants of the receptor desensitization and deactivation were also significantly attenuated by riluzole. G-protein inhibitors (pertussis toxin and guanosine 5'-[beta-thio] diphosphate) did not completely block these inhibitory actions of riluzole. These results indicate that riluzole inhibits 5-HT3-induced ion currents directly by slowing channel activation in NCB-20 neuroblastoma cells.
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Affiliation(s)
- Ki Jung Kim
- Department of Pharmacology, Medical Research Center, College of Medicine, The Catholic University of Korea, Korea
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Relationship between three serotonin receptor subtypes (HTR3A, HTR2A and HTR4) and treatment-resistant schizophrenia in the Japanese population. Neurosci Lett 2008; 435:95-8. [DOI: 10.1016/j.neulet.2008.01.083] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2007] [Accepted: 01/31/2008] [Indexed: 11/23/2022]
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Candelario-Jalil E, Muñoz E, Fiebich BL. Detrimental effects of tropisetron on permanent ischemic stroke in the rat. BMC Neurosci 2008; 9:19. [PMID: 18254974 PMCID: PMC2259310 DOI: 10.1186/1471-2202-9-19] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2007] [Accepted: 02/06/2008] [Indexed: 12/30/2022] Open
Abstract
Background Recent in vitro evidence indicates that blockade of 5-hydroxytryptamine (5-HT) receptor 3 (5-HT3) is able to confer protection in different models of neuronal injury. The purpose of the present study was to investigate the effect of tropisetron, a 5-HT3 receptor antagonist, on infarct size and neurological score in a model of ischemic stroke induced by permanent middle cerebral artery occlusion (pMCAO) in the rat. Methods Two different doses of tropisetron (5 and 10 mg/kg) or vehicle were administered intraperitoneally 30 min before pMCAO. Neurological deficit scores, mortality rate and infarct volume were determined 24 h after permanent focal cerebral ischemia. Results Tropisetron failed to reduce cerebral infarction. Animals receiving tropisetron showed a significant increase (p < 0.05) in neurological deficits and mortality rate. Conclusion Data from this study indicate that blockade of 5-HT3 receptors with tropisetron worsens ischemic brain injury induced by pMCAO. These findings could have important clinical implications. Patients taking tropisetron, and possibly other 5-HT3 antagonists, could potentially have a worse outcome following a brain infarct.
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Affiliation(s)
- Eduardo Candelario-Jalil
- Neurochemistry Research Group, Department of Psychiatry, University of Freiburg Medical School, Hauptstr, 5, D-79104 Freiburg, Germany.
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Abstract
The release of transmitters through vesicle exocytosis from nerve terminals is not constant but is subject to modulation by various mechanisms, including prior activity at the synapse and the presence of neurotransmitters or neuromodulators in the synapse. Instantaneous responses of postsynaptic cells to released transmitters are mediated by ionotropic receptors. In contrast to metabotropic receptors, ionotropic receptors mediate the actions of agonists in a transient manner within milliseconds to seconds. Nevertheless, transmitters can control vesicle exocytosis not only via slowly acting metabotropic, but also via fast acting ionotropic receptors located at the presynaptic nerve terminals. In fact, members of the following subfamilies of ionotropic receptors have been found to control transmitter release: ATP P2X, nicotinic acetylcholine, GABA(A), ionotropic glutamate, glycine, 5-HT(3), andvanilloid receptors. As these receptors display greatly diverging structural and functional features, a variety of different mechanisms are involved in the regulation of transmitter release via presynaptic ionotropic receptors. This text gives an overview of presynaptic ionotropic receptors and briefly summarizes the events involved in transmitter release to finally delineate the most important signaling mechanisms that mediate the effects of presynaptic ionotropic receptor activation. Finally, a few examples are presented to exemplify the physiological and pharmacological relevance of presynaptic ionotropic receptors.
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Affiliation(s)
- M M Dorostkar
- Institute of Experimental and Clinical Pharmacology, Medical University of Graz, Universitäts-platz 4, Graz, Austria
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Choi IS, Cho JH, Kim JT, Park EJ, Lee MG, Shin HI, Choi BJ, Jang IS. Serotoninergic modulation of GABAergic synaptic transmission in developing rat CA3 pyramidal neurons. J Neurochem 2007; 103:2342-53. [PMID: 17931361 DOI: 10.1111/j.1471-4159.2007.04945.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Serotoninergic modulation of GABAergic mIPSCs was investigated in immature (postnatal 12-16-days old) rat CA3 pyramidal neurons using a conventional whole-cell patch clamp technique. Serotonin or 5-hydroxytryptamine (5-HT) (10 micromol/L) transiently and explosively increased mIPSC frequency with a small increase in the current amplitude. However, 5-HT did not affect the GABA-induced postsynaptic currents, indicating that 5-HT acts presynaptically to facilitate the probability of spontaneous GABA release. The 5-HT action on GABAergic mIPSC frequency was completely blocked by 100 nmol/L MDL72222, a selective 5-HT(3) receptor antagonist, and mimicked by mCPBG, a selective 5-HT(3) receptor agonist. The 5-HT action on GABAergic mIPSC frequency was completely occluded either in the presence of 200 mumol/L Cd2+ or in the Na+-free external solution, suggesting that the 5-HT(3) receptor-mediated facilitation of mIPSC frequency requires a Ca2+ influx passing through voltage-dependent Ca2+ channels from the extracellular space, and that presynaptic 5-HT(3) receptors are less permeable to Ca2+. The 5-HT action on mIPSC frequency in the absence or presence of extracellular Na+ gradually increased with postnatal development. Such a developmental change in the 5-HT(3) receptor-mediated facilitation of GABAergic transmission would play important roles in the regulation of excitability as well as development in CA3 pyramidal neurons.
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Affiliation(s)
- In-Sun Choi
- Department of Pharmacology, School of Dentistry, Kyungpook National University, Republic of Korea
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Ho SSN, Chow BKC, Yung WH. Serotonin increases the excitability of the hypothalamic paraventricular nucleus magnocellular neurons. Eur J Neurosci 2007; 25:2991-3000. [PMID: 17561813 DOI: 10.1111/j.1460-9568.2007.05547.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Recent evidence that 5-hydroxytryptamine (5-HT or serotonin) enhances the release and the gene expression of vasopressin and oxytocin in the hypothalamic paraventricular nucleus (PVN) suggests that 5-HT can excite the PVN magnocellular neurons. The objective of this study was to examine the underlying mechanisms for such excitatory action in the electrophysiologically identified hypothalamic PVN magnocellular neurons in rats using whole-cell patch-clamp. We found that 5-HT weakly depolarizes 33.3% of PVN magnocellular neurons in the presence of tetrodotoxin. A minuscule inward current was produced by 5-HT in 48% of the cells, which was attenuated when the 5-HT(4) antagonist GR113808 or the 5-HT(7) antagonist SB269970 was added. In addition, 5-HT reduced the frequency of miniature inhibitory postsynaptic currents in a dose-dependent manner. This inhibition was mimicked by the 5-HT(1B) agonist CP93129, and reversed in the presence of 5-HT(1B) antagonists cyanopindolol and SB224289. Besides, 5-HT induced a biphasic effect on the frequency of miniature excitatory postsynaptic currents, comprising a transient inhibition and a delayed concentration-dependent excitation (onset latency approximately 5 min). The facilitation was mimicked by the 5-HT(2A/2C) agonist DOI and abolished in the presence of the 5-HT(2C) antagonist RS102221. Our findings reveal that 5-HT directly increases the excitability of the PVN magnocellular neurons via multiple receptor subtypes and mechanisms. This may help understanding the regulation of 5-HT-induced hormone release and feeding behavior in the PVN.
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Affiliation(s)
- Sara S N Ho
- Department of Zoology, The University of Hong Kong, Pokfulam, Hong Kong, China
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De Gobbi JIF, Martinez G, Barbosa SP, Beltz TG, De Luca LA, Thunhorst RL, Johnson AK, Vanderlei Menani J. 5-HT2 and 5-HT3 receptors in the lateral parabrachial nucleus mediate opposite effects on sodium intake. Neuroscience 2007; 146:1453-61. [PMID: 17434681 DOI: 10.1016/j.neuroscience.2007.03.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2006] [Revised: 02/05/2007] [Accepted: 03/08/2007] [Indexed: 11/27/2022]
Abstract
The present study investigated the role of several 5-HT receptor subtypes in the lateral parabrachial nucleus (LPBN) in the control of sodium appetite (i.e. NaCl consumption). Male Holtzman rats had cannulas implanted bilaterally into the LPBN for the injection of 5-HT receptor agonists and antagonists in conjunction with either acute fluid depletion or 24-h sodium depletion. Following these treatments, access to 0.3 M NaCl was provided and the intakes of saline and water were measured for the next 2 h. Bilateral injections of the 5-HT2A receptor antagonist, ketanserin or the 5-HT2C receptor antagonist, mianserin into the LPBN increased 0.3 M NaCl intake without affecting water intake induced by acute fluid-depletion. Bilateral injections of the 5-HT2B receptor agonist, BW723C86 hydrochloride, had no effect on 0.3 M NaCl or water intake under these conditions. Treatment of the LPBN with the 5-HT2B/2C receptor agonist, 2-(2-methyl-4-clorophenoxy) propanoic acid (mCPP) caused dose-related reductions in 0.3 M NaCl intake after 24 h sodium depletion. The effects of mCPP were prevented by pretreating the LPBN with the 5-HT2B/2C receptor antagonist, SDZSER082. Activation of 5-HT3 receptors by the receptor agonist, 1-phenylbiguanide (PBG) caused dose-related increases in 0.3 M NaCl intake. Pretreatment of the LPBN with the 5-HT3 receptor antagonist, 1-methyl-N-[8-methyl-8-azabicyclo (3.2.1)-oct-3-yl]-1H-indazole-3-carboxamide (LY-278,584) abolished the effects of PBG, but LY-278,584 had no effects on sodium or water intake when injected by itself. PBG injected into the LPBN did not alter intake of palatable 0.06 M sucrose in fluid replete rats. The results suggest that activation of the 5-HT2A and 5-HT2C receptor subtypes inhibits sodium ingestion. In contrast, activation of the 5-HT3 receptor subtype increases sodium ingestion. Therefore, multiple serotonergic receptor subtypes in the LPBN are implicated in the control of sodium intake, sometimes by mediating opposite effects of 5-HT. The results provide new information concerning the control of sodium intake by LPBN mechanisms.
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Affiliation(s)
- J I F De Gobbi
- Department of Physiology, Bioscience Institute, Paulista State University (UNESP), Distrito de Rubião Junior, s/n, 18618-000 Botucatu, SP, Brazil.
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Rüsch D, Musset B, Wulf H, Schuster A, Raines DE. Subunit-dependent modulation of the 5-hydroxytryptamine type 3 receptor open-close equilibrium by n-alcohols. J Pharmacol Exp Ther 2007; 321:1069-74. [PMID: 17360702 DOI: 10.1124/jpet.106.118752] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
5-Hydroxytryptamine (5-HT, serotonin) type 3 (5-HT(3)) receptors belong to the alcohol-sensitive superfamily of Cys-loop ligand-gated ion channels, and they are thought to play an important role in alcoholism. Alcohols with small molecular volumes increase the amplitude of currents evoked by low 5-HT concentrations and shift the 5-HT concentration-response curve for 5-HT(3) receptor activation leftward, indicative of increased receptor sensitivity to agonist. This action is significantly smaller when currents are mediated by heteromeric 5-HT(3AB) receptors compared with homomeric 5-HT(3A) receptors. In this study, we used the highly inefficacious 5-HT(3) receptor agonist dopamine to determine whether this difference between 5-HT(3A) and 5-HT(3AB) receptors reflects differential alcohol modulation of agonist binding affinity or channel gating efficacy. Human recombinant 5-HT(3A) and 5-HT(3AB) receptors were expressed in Xenopus oocytes, and currents were measured in the absence and presence of alcohols using the two-electrode voltage-clamp technique. Modulation by alcohols of peak currents elicited by maximally activating concentrations of dopamine was alcohol concentration-dependent. Potentiation by smaller alcohols was consistently significantly greater in 5-HT(3A) than in 5-HT(3AB) receptors, whereas inhibition by larger alcohols was not. A representative small (butanol) and large (octanol) alcohol failed to alter the EC(50) value for channel activation by dopamine. We conclude that the presence of the 5-HT(3B) subunit in 5-HT(3AB) receptors significantly reduces the enhancement of gating efficacy by small alcohols without altering the inhibitory actions of large alcohols.
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Affiliation(s)
- Dirk Rüsch
- Department of Anesthesia and Critical Care, University Hospital Giessen-Marburg GmbH, Marburg Campus, Baldingerstrasse, 35033 Marburg, Germany.
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Bianchi C, Marani L, Marino S, Barbieri M, Nazzaro C, Beani L, Siniscalchi A. Serotonin modulation of cell excitability and of [3H]GABA and [3H]D-aspartate efflux in primary cultures of rat cortical neurons. Neuropharmacology 2006; 52:995-1002. [PMID: 17156800 DOI: 10.1016/j.neuropharm.2006.10.017] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2006] [Revised: 10/25/2006] [Accepted: 10/28/2006] [Indexed: 11/25/2022]
Abstract
The effects of 5-hydroxytryptamine (5-HT) on neuronal excitability, evaluated as depolarization-induced firing rate, and on amino acid release, measured as electrically-evoked [(3)H]GABA and [(3)H]d-aspartate efflux, were investigated in rat primary cortical neuronal cultures. 5-HT displayed a concentration-dependent, bimodal effect on neuronal excitability: at 3-10microM it increased excitability through 5-HT(2A) receptors, and was blocked by the selective 5-HT(2A) antagonist MDL 100907, whereas at 30-100microM it reduced excitability through 5-HT(1A) receptors, and was, in turn, blocked by the selective 5-HT(1A) antagonist WAY 100135. The electrically-evoked [(3)H]GABA efflux was concentration-dependently inhibited by 5-HT (pEC(50)=4.74) and such inhibition was prevented by WAY 100135, but not by GR 55562, a selective 5-HT(1D/B) receptor antagonist. Conversely, 5-HT concentration-dependently increased stimulus-evoked [(3)H]d-aspartate efflux (pEC(50)=4.71). The increase was facilitated by methiothepin and was reversed into inhibition by ICS 205930, a selective 5-HT(3) receptor antagonist. In the presence of ICS 205930, the inhibition induced by 5-HT was prevented by the selective 5-HT(1D/B) receptor antagonist GR 55562, but not by WAY 100135. These findings suggest that 5-HT inhibits GABA release through 5-HT(1A) receptors and exerts a dual modulation on glutamate release, mostly facilitatory (through 5-HT(3) receptors) but also inhibitory (through 5-HT(1D/B) receptors), leading to a prevalently positive modulation of the excitatory signal by amino acid neurotransmitter containing neurons.
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Affiliation(s)
- C Bianchi
- Department of Clinical and Experimental Medicine, Section of Pharmacology and Neuroscience Center, University of Ferrara, Via Fossato di Mortara 17-19, 44100 Ferrara, Italy
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