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Chahl LA. TRPV1 Channels in the Central Nervous System as Drug Targets. Pharmaceuticals (Basel) 2024; 17:756. [PMID: 38931423 PMCID: PMC11206835 DOI: 10.3390/ph17060756] [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: 03/30/2024] [Revised: 05/14/2024] [Accepted: 06/05/2024] [Indexed: 06/28/2024] Open
Abstract
TRPV1 channels are polymodal cation channels located predominantly on primary afferent neurons that are activated by inflammatory mediators, capsaicin (the active component in chili peppers), and noxious heat. TRPV1 channel antagonists are potential new analgesic agents, but their development has been hindered by the finding that they also produce loss of thermal homeostasis and response to noxious heat. Results from recent studies of the TRPV1 channel indicate that it might be possible to develop TRPV1 channel antagonists that inhibit pain without affecting noxious heat sensation. TRPV1 channels are also present in the central nervous system (CNS) and have been implicated in learning, memory, and behaviour. TRPV1 channel modulators have been proposed to have possible therapeutic potential in the treatment of neurological and psychiatric conditions. However, further understanding of the role of TRPV1 channels in the CNS is required before therapeutic advances in the treatment of neuropsychiatric conditions with TRPV1 channel modulators can be made.
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Affiliation(s)
- Loris A Chahl
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW 2308, Australia
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2
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Socała K, Jakubiec M, Abram M, Mlost J, Starowicz K, Kamiński RM, Ciepiela K, Andres-Mach M, Zagaja M, Metcalf CS, Zawadzki P, Wlaź P, Kamiński K. TRPV1 channel in the pathophysiology of epilepsy and its potential as a molecular target for the development of new antiseizure drug candidates. Prog Neurobiol 2024; 240:102634. [PMID: 38834133 DOI: 10.1016/j.pneurobio.2024.102634] [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: 10/25/2023] [Revised: 04/26/2024] [Accepted: 05/28/2024] [Indexed: 06/06/2024]
Abstract
Identification of transient receptor potential cation channel, subfamily V member 1 (TRPV1), also known as capsaicin receptor, in 1997 was a milestone achievement in the research on temperature sensation and pain signalling. Very soon after it became evident that TRPV1 is implicated in a wide array of physiological processes in different peripheral tissues, as well as in the central nervous system, and thereby could be involved in the pathophysiology of numerous diseases. Increasing evidence suggests that modulation of TRPV1 may also affect seizure susceptibility and epilepsy. This channel is localized in brain regions associated with seizures and epilepsy, and its overexpression was found both in animal models of seizures and in brain samples from epileptic patients. Moreover, modulation of TRPV1 on non-neuronal cells (microglia, astrocytes, and/or peripheral immune cells) may have an impact on the neuroinflammatory processes that play a role in epilepsy and epileptogenesis. In this paper, we provide a comprehensive and critical overview of currently available data on TRPV1 as a possible molecular target for epilepsy management, trying to identify research gaps and future directions. Overall, several converging lines of evidence implicate TRPV1 channel as a potentially attractive target in epilepsy research but more studies are needed to exploit the possible role of TRPV1 in seizures/epilepsy and to evaluate the value of TRPV1 ligands as candidates for new antiseizure drugs.
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Affiliation(s)
- Katarzyna Socała
- Department of Animal Physiology and Pharmacology, Institute of Biological Sciences, Maria Curie-Skłodowska University, Akademicka 19, Lublin PL 20-033, Poland.
| | - Marcin Jakubiec
- Department of Medicinal Chemistry, Faculty of Pharmacy, Jagiellonian University Medical College, Medyczna 9, Cracow PL 30-688, Poland
| | - Michał Abram
- Department of Medicinal Chemistry, Faculty of Pharmacy, Jagiellonian University Medical College, Medyczna 9, Cracow PL 30-688, Poland
| | - Jakub Mlost
- Department of Neurochemistry, Maj Institute of Pharmacology, Polish Academy of Sciences, Smętna 12, Cracow PL 31-343, Poland
| | - Katarzyna Starowicz
- Department of Neurochemistry, Maj Institute of Pharmacology, Polish Academy of Sciences, Smętna 12, Cracow PL 31-343, Poland
| | - Rafał M Kamiński
- Department of Medicinal Chemistry, Faculty of Pharmacy, Jagiellonian University Medical College, Medyczna 9, Cracow PL 30-688, Poland
| | - Katarzyna Ciepiela
- Department of Medicinal Chemistry, Faculty of Pharmacy, Jagiellonian University Medical College, Medyczna 9, Cracow PL 30-688, Poland; Selvita S.A., Bobrzyńskiego 14, Cracow PL 30-348, Poland
| | - Marta Andres-Mach
- Department of Experimental Pharmacology, Institute of Rural Health, Jaczewskiego 2, Lublin PL 20-090, Poland
| | - Mirosław Zagaja
- Department of Experimental Pharmacology, Institute of Rural Health, Jaczewskiego 2, Lublin PL 20-090, Poland
| | - Cameron S Metcalf
- Department of Pharmacology and Toxicology, University of Utah, Salt Lake City, UT 84112, USA
| | - Przemysław Zawadzki
- Department of Medicinal Chemistry, Faculty of Pharmacy, Jagiellonian University Medical College, Medyczna 9, Cracow PL 30-688, Poland
| | - Piotr Wlaź
- Department of Animal Physiology and Pharmacology, Institute of Biological Sciences, Maria Curie-Skłodowska University, Akademicka 19, Lublin PL 20-033, Poland
| | - Krzysztof Kamiński
- Department of Medicinal Chemistry, Faculty of Pharmacy, Jagiellonian University Medical College, Medyczna 9, Cracow PL 30-688, Poland
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3
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Yang F, Sivils A, Cegielski V, Singh S, Chu XP. Transient Receptor Potential (TRP) Channels in Pain, Neuropsychiatric Disorders, and Epilepsy. Int J Mol Sci 2023; 24:ijms24054714. [PMID: 36902145 PMCID: PMC10003176 DOI: 10.3390/ijms24054714] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Revised: 02/21/2023] [Accepted: 02/22/2023] [Indexed: 03/05/2023] Open
Abstract
Pharmacomodulation of membrane channels is an essential topic in the study of physiological conditions and disease status. Transient receptor potential (TRP) channels are one such family of nonselective cation channels that have an important influence. In mammals, TRP channels consist of seven subfamilies with a total of twenty-eight members. Evidence shows that TRP channels mediate cation transduction in neuronal signaling, but the full implication and potential therapeutic applications of this are not entirely clear. In this review, we aim to highlight several TRP channels which have been shown to mediate pain sensation, neuropsychiatric disorders, and epilepsy. Recent findings suggest that TRPM (melastatin), TRPV (vanilloid), and TRPC (canonical) are of particular relevance to these phenomena. The research reviewed in this paper validates these TRP channels as potential targets of future clinical treatment and offers patients hope for more effective care.
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Neostriatum neuronal TRPV 1-signalling mediates striatal anandamide at high concentration facilitatory influence on neostriato-nigral dishinhibitory GABAergic connections. Brain Res Bull 2023; 192:128-141. [PMID: 36414159 DOI: 10.1016/j.brainresbull.2022.11.014] [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: 05/30/2022] [Revised: 11/14/2022] [Accepted: 11/17/2022] [Indexed: 11/21/2022]
Abstract
RATIONALE Several lines of evidence have demonstrated that the cannabinoid type 1 receptor (CB1) is found in the caudate nucleus and putamen (CPu) in addition to the substantia nigra pars reticulata (SNpr). Here, we investigated the role of endocannabinoid neuromodulation of striato-nigral disinhibitory projections on the activity of nigro-collicular GABAergic pathways that control the expression of unconditioned fear-related behavioural responses elicited by microinjections of the GABAA receptor selective antagonist bicuculline (BIC) in the deep layers of the superior colliculus (dlSC). METHODS Fluorescent neural tract tracers were deposited in either CPu or in SNpr. Wistar rats received injection of vehicle, anandamide (AEA), either at low (50 pmol) or high (100 pmol) concentrations in CPu followed by bicuculline microinjections in dlSC. RESULTS Connections between CPu, the SNpr and dlSC were demonstrated. The GABAA receptor blockade in dlSC elicited panic-like behaviour. AEA at the lowest concentration caused a panicolytic-like effect that was antagonised by the CPu pretreatment with AM251 at 100 pmol. AEA at the highest concentration caused a panicogenic-like effect that was antagonised by the CPu pretreatment with 6-iodonordihydrocapsaicin (6-I-CPS) at different concentrations (0.6, 6, 60 nmol). CONCLUSION These findings suggest that while pre-synaptic CB1-signalling subserves an indirect facilitatory effect of AEA on striato-nigral pathways causing panicolytic-like responses through midbrain tectum enhanced activity, post-synaptic TRPV1-signalling in CPu mediates AEA direct activation of striato-nigral disinhibitory pathways resulting in increasing dlSC neurons activity and a panicogenic-like response. All these actions seem to depend on the interface with the nigro-collicular inhibitory GABAergic pathways.
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5
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Villar-Martinez MD, Goadsby PJ. Pathophysiology and Therapy of Associated Features of Migraine. Cells 2022; 11:cells11172767. [PMID: 36078174 PMCID: PMC9455236 DOI: 10.3390/cells11172767] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Revised: 08/30/2022] [Accepted: 08/31/2022] [Indexed: 11/16/2022] Open
Abstract
Migraine is a complex and debilitating disorder that is broadly recognised by its characteristic headache. However, given the wide array of clinical presentations in migraineurs, the headache might not represent the main troublesome symptom and it can even go unnoticed. Understanding migraines exclusively as a pain process is simplistic and certainly hinders management. We describe the mechanisms behind some of the most disabling associated symptoms of migraine, including the relationship between the central and peripheral processes that take part in nausea, osmophobia, phonophobia, vertigo and allodynia. The rationale for the efficacy of the current therapeutic arsenal is also depicted in this article. The associated symptoms to migraine, apart from the painful component, are frequent, under-recognised and can be more deleterious than the headache itself. The clinical anamnesis of a headache patient should enquire about the associated symptoms, and treatment should be considered and individualised. Acknowledging the associated symptoms as a fundamental part of migraine has permitted a deeper and more coherent comprehension of the pathophysiology of migraine.
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Affiliation(s)
- Maria Dolores Villar-Martinez
- Headache Group, Wolfson CARD, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London WC2R 2LS, UK
- NIHR King’s Clinical Research Facility, SLaM Biomedical Research Centre, King’s College Hospital, London SE5 9RS, UK
| | - Peter J. Goadsby
- Headache Group, Wolfson CARD, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London WC2R 2LS, UK
- NIHR King’s Clinical Research Facility, SLaM Biomedical Research Centre, King’s College Hospital, London SE5 9RS, UK
- Department of Neurology, University of California, Los Angeles, CA 90095, USA
- Correspondence:
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6
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Meza RC, Ancatén-González C, Chiu CQ, Chávez AE. Transient Receptor Potential Vanilloid 1 Function at Central Synapses in Health and Disease. Front Cell Neurosci 2022; 16:864828. [PMID: 35518644 PMCID: PMC9062234 DOI: 10.3389/fncel.2022.864828] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Accepted: 03/29/2022] [Indexed: 12/11/2022] Open
Abstract
The transient receptor potential vanilloid 1 (TRPV1), a ligand-gated nonselective cation channel, is well known for mediating heat and pain sensation in the periphery. Increasing evidence suggests that TRPV1 is also expressed at various central synapses, where it plays a role in different types of activity-dependent synaptic changes. Although its precise localizations remain a matter of debate, TRPV1 has been shown to modulate both neurotransmitter release at presynaptic terminals and synaptic efficacy in postsynaptic compartments. In addition to being required in these forms of synaptic plasticity, TRPV1 can also modify the inducibility of other types of plasticity. Here, we highlight current evidence of the potential roles for TRPV1 in regulating synaptic function in various brain regions, with an emphasis on principal mechanisms underlying TRPV1-mediated synaptic plasticity and metaplasticity. Finally, we discuss the putative contributions of TRPV1 in diverse brain disorders in order to expedite the development of next-generation therapeutic treatments.
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Affiliation(s)
- Rodrigo C Meza
- Centro Interdisciplinario de Neurociencia de Valparaíso (CINV), Instituto de Neurociencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Carlos Ancatén-González
- Centro Interdisciplinario de Neurociencia de Valparaíso (CINV), Instituto de Neurociencias, Universidad de Valparaíso, Valparaíso, Chile.,Programa de Doctorado en Ciencias, Mención Neurociencia, Universidad de Valparaíso, Valparaíso, Chile
| | - Chiayu Q Chiu
- Centro Interdisciplinario de Neurociencia de Valparaíso (CINV), Instituto de Neurociencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Andrés E Chávez
- Centro Interdisciplinario de Neurociencia de Valparaíso (CINV), Instituto de Neurociencias, Universidad de Valparaíso, Valparaíso, Chile
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7
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Iglesias LP, Aguiar DC, Moreira FA. TRPV1 blockers as potential new treatments for psychiatric disorders. Behav Pharmacol 2022; 33:2-14. [PMID: 33136616 DOI: 10.1097/fbp.0000000000000603] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The transient receptor potential vanilloid-1 channel (TRPV1) is responsible for decoding physical and chemical stimuli. TRPV1 is activated by capsaicin (a compound from chili peppers), heat (above 43°C) and acid environment, playing a major role in pain, inflammation and body temperature. Molecular and histological studies have suggested TRPV1 expression in specific brain regions, where it can be activated primarily by the endocannabinoid anandamide, fostering studies on its potential role in psychiatric disorders. TRPV1 blockers are effective in various animal models predictive of anxiolytic and antipanic activities, in addition to reducing conditioned fear. In models of antidepressant activity, these compounds reduce behavioral despair and promote active stress-coping behavior. TRPV1 blockers also reduce the effects of certain drugs of abuse and revert behavioral changes in animal models of neurodevelopmental disorders. The main limiting factor in developing TRPV1 blockers as therapeutic agents concerns their effects on body temperature, particularly hyperthermia. New compounds, which block specific states of the channel, could represent an alternative. Moreover, compounds blocking both TRPV1 and the anandamide-hydrolyzing enzyme, fatty acid amide hydrolase (FAAH), termed dual TRPV1/FAAH blockers, have been investigated with promising results. Overall, preclinical studies yield favorable results with TRPV1 blockers in animal models of psychiatric disorders.
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Affiliation(s)
- Lia P Iglesias
- Department of Pharmacology, Graduate School of Neuroscience
- Department of Pharmacology, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gera, Brazil
| | - Daniele C Aguiar
- Department of Pharmacology, Graduate School of Neuroscience
- Department of Pharmacology, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gera, Brazil
| | - Fabrício A Moreira
- Department of Pharmacology, Graduate School of Neuroscience
- Department of Pharmacology, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gera, Brazil
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8
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Paula BD, Vieira-Rasteli E, Calvo F, Coimbra N, Leite-Panissi C. Functional activation of the periaqueductal gray matter during conditioned and unconditioned fear in guinea pigs confronted with the Boa constrictor constrictor snake. Braz J Med Biol Res 2022; 55:e11542. [PMID: 35195195 PMCID: PMC8856599 DOI: 10.1590/1414-431x2021e11542] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2021] [Accepted: 12/06/2021] [Indexed: 11/22/2022] Open
Abstract
The periaqueductal gray matter (PAG) is an essential structure involved in the
elaboration of defensive responses, such as when facing predators and
conspecific aggressors. Using a prey vs predator paradigm, we
aimed to evaluate the PAG activation pattern evoked by unconditioned and
conditioned fear situations. Adult male guinea pigs were confronted either by a
Boa constrictor constrictor wild snake or by the aversive
experimental context. After the behavioral test, the rodents were euthanized and
the brain prepared for immunohistochemistry for Fos protein identification in
different PAG columns. Although Fos-protein-labeled neurons were found in
different PAG columns after both unconditioned and conditioned fear situations
at the caudal level of the PAG, we found greater activation of the lateral
column compared to the ventrolateral and dorsomedial columns after predator
exposure. Moreover, the lateral column of the PAG showed higher Fos-labeled
cells at the caudal level compared to the same area at the rostral level. The
present results suggested that there are different activation patterns of PAG
columns during unconditioned and conditioned fear in guinea pigs. It is possible
to hypothesize that the recruitment of specific PAG columns depended on the
nature of the threatening stimulus.
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Affiliation(s)
| | | | - F. Calvo
- Universidade de São Paulo, Brasil; Universidade de São Paulo, Brasil
| | - N.C. Coimbra
- Universidade de São Paulo, Brasil; Universidade de São Paulo, Brasil; Instituto de Neurociências e Comportamento, Brasil; Universidade de São Paulo, Brasil
| | - C.R.A. Leite-Panissi
- Universidade de São Paulo, Brasil; Universidade de São Paulo, Brasil; Instituto de Neurociências e Comportamento, Brasil
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9
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Escelsior A, Sterlini B, Murri MB, Serafini G, Aguglia A, da Silva BP, Corradi A, Valente P, Amore M. Red-hot chili receptors: A systematic review of TRPV1 antagonism in animal models of psychiatric disorders and addiction. Behav Brain Res 2020; 393:112734. [DOI: 10.1016/j.bbr.2020.112734] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Revised: 05/19/2020] [Accepted: 05/22/2020] [Indexed: 12/17/2022]
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10
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Endocannabinoid neuromodulation in the neostriatum decreases the GABAergic striato-nigral disinhibitory function and increases the nigro-collicular inhibitory pathway activity. J Neural Transm (Vienna) 2020; 127:1199-1208. [DOI: 10.1007/s00702-020-02217-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2019] [Accepted: 06/02/2020] [Indexed: 02/06/2023]
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Dos Anjos-Garcia T, Coimbra NC. Opposing roles of dorsomedial hypothalamic CB1 and TRPV1 receptors in anandamide signaling during the panic-like response elicited in mice by Brazilian rainbow Boidae snakes. Psychopharmacology (Berl) 2019; 236:1863-1874. [PMID: 30694375 DOI: 10.1007/s00213-019-5170-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Accepted: 01/14/2019] [Indexed: 12/23/2022]
Abstract
RATIONALE The endocannabinoid system plays an important role in the organization of panic-like defensive behavior. Threatening situations stimulate brain areas, such as the dorsomedial hypothalamus (DMH). However, there is a lack of studies addressing the role of the DMH endocannabinoid system in panic-like responses. OBJECTIVES We aimed to verify which mechanisms underlie anandamide-mediated responses in the DMH. METHODS To test the hypothesis that the anandamide produces panicolytic-like effects, we treated mice with intra-DMH microinjections of vehicle or increasing doses of anandamide (0.5, 5, or 50 pmol) and then performed confrontation with the South American snake Epicrates cenchria assisi. RESULTS Intra-DMH anandamide treatment yielded a U-shaped dose-response curve with no effect of the lowest (0.5 pmol) or the highest (50 pmol) dose and significant inhibition of panic-like responses at the intermediate (5 pmol) dose. In addition, this panicolytic-like effect was prevented by pretreatment of the DMH with the CB1 receptor antagonist AM251 (100 pmol). However, pretreatment of the DMH with the TRPV1 receptor antagonist 6-iodo-nordihydrocapsaicin (3 nmol) restored the panicolytic-like effect of the highest dose of anandamide. Immunohistochemistry revealed that CB1 receptors were present primarily on axonal fibers, while TRPV1 receptors were found almost exclusively surrounding the perikarya in DMH. CONCLUSIONS The present results suggest that anandamide exerts a panicolytic-like effect in the DMH by activation of CB1 receptors and that TRPV1 receptors are related to the lack of effect of the highest dose of anandamide.
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Affiliation(s)
- Tayllon Dos Anjos-Garcia
- Laboratory of Neuroanatomy and Neuropsychobiology, Department of Pharmacology, Ribeirão Preto Medical School of the University of São Paulo (FMRP-USP), Av. Bandeirantes 3900, Ribeirão Preto, São Paulo, 14049-900, Brazil.,NAP-USP-Neurobiology of Emotions Research Centre (NuPNE), Ribeirão Preto Medical School of the University of São Paulo (FMRP-USP), Av. Bandeirantes, 3900, Ribeirão Preto, São Paulo, 14049-900, Brazil.,Ophidiarium LNN-FMRP-USP/INeC, Ribeirão Preto School of Medicine of the University of São Paulo (FMRP-USP), Av. Bandeirantes, 3900, Ribeirão Preto, São Paulo, 14049-900, Brazil
| | - Norberto Cysne Coimbra
- Laboratory of Neuroanatomy and Neuropsychobiology, Department of Pharmacology, Ribeirão Preto Medical School of the University of São Paulo (FMRP-USP), Av. Bandeirantes 3900, Ribeirão Preto, São Paulo, 14049-900, Brazil. .,NAP-USP-Neurobiology of Emotions Research Centre (NuPNE), Ribeirão Preto Medical School of the University of São Paulo (FMRP-USP), Av. Bandeirantes, 3900, Ribeirão Preto, São Paulo, 14049-900, Brazil. .,Ophidiarium LNN-FMRP-USP/INeC, Ribeirão Preto School of Medicine of the University of São Paulo (FMRP-USP), Av. Bandeirantes, 3900, Ribeirão Preto, São Paulo, 14049-900, Brazil. .,Behavioural Neuroscience Institute (INeC), Av. do Café, 2450, Ribeirão Preto, São Paulo, 14050-220, Brazil.
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12
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Back FP, Carobrez AP. Periaqueductal gray glutamatergic, cannabinoid and vanilloid receptor interplay in defensive behavior and aversive memory formation. Neuropharmacology 2018; 135:399-411. [DOI: 10.1016/j.neuropharm.2018.03.032] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Revised: 03/07/2018] [Accepted: 03/23/2018] [Indexed: 11/29/2022]
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13
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Thakre PP, Bellingham MC. Capsaicin Enhances Glutamatergic Synaptic Transmission to Neonatal Rat Hypoglossal Motor Neurons via a TRPV1-Independent Mechanism. Front Cell Neurosci 2017; 11:383. [PMID: 29259542 PMCID: PMC5723349 DOI: 10.3389/fncel.2017.00383] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Accepted: 11/17/2017] [Indexed: 01/02/2023] Open
Abstract
We investigated whether capsaicin modulated synaptic transmission to hypoglossal motor neurons (HMNs) by acting on transient receptor potential vanilloid type 1 (TRPV1) receptors. Using whole-cell patch clamp recording from neonatal rat HMNs, we found that capsaicin increased spontaneous excitatory post-synaptic current (sEPSC) frequency and amplitude. Interestingly, the only effect of capsaicin on spontaneous inhibitory post-synaptic currents (sIPSCs) was a significant decrease in sIPSC amplitude without altering frequency, indicating a post-synaptic mechanism of action. The frequency of miniature excitatory post-synaptic currents (mEPSCs), recorded in the presence of tetrodotoxin (TTX), was also increased by capsaicin, but capsaicin did not alter mEPSC amplitude, consistent with a pre-synaptic mechanism of action. A negative shift in membrane current (Iholding) was elicited by capsaicin under both recording conditions. The effect of capsaicin on excitatory synaptic transmission remained unchanged in the presence of the TRPV1 antagonists, capsazepine or SB366791, suggesting that capsaicin acts to modulate EPSCs via a mechanism which does not require TRPV1 activation. Capsaicin, however, did not alter evoked excitatory post-synaptic currents (eEPSCs) or the paired-pulse ratio (PPR) of eEPSCs. Repetitive action potential (AP) firing in HMNs was also unaltered by capsaicin, indicating that capsaicin does not change HMN intrinsic excitability. We have demonstrated that capsaicin modulates glutamatergic excitatory, as well as glycinergic inhibitory, synaptic transmission in HMNs by differing pre- and post-synaptic mechanisms. These results expand our understanding regarding the extent to which capsaicin can modulate synaptic transmission to central neurons.
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Affiliation(s)
- Prajwal P Thakre
- Faculty of Medicine, School of Biomedical Sciences, The University of Queensland, Brisbane, QLD, Australia
| | - Mark C Bellingham
- Faculty of Medicine, School of Biomedical Sciences, The University of Queensland, Brisbane, QLD, Australia
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14
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Acta Neuropsychiatrica and social media. Acta Neuropsychiatr 2017; 29:323. [PMID: 29151405 DOI: 10.1017/neu.2017.30] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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