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Sa M, Yoo ES, Koh W, Park MG, Jang HJ, Yang YR, Bhalla M, Lee JH, Lim J, Won W, Kwon J, Kwon JH, Seong Y, Kim B, An H, Lee SE, Park KD, Suh PG, Sohn JW, Lee CJ. Hypothalamic GABRA5-positive neurons control obesity via astrocytic GABA. Nat Metab 2023; 5:1506-1525. [PMID: 37653043 DOI: 10.1038/s42255-023-00877-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Accepted: 07/25/2023] [Indexed: 09/02/2023]
Abstract
The lateral hypothalamic area (LHA) regulates food intake and energy balance. Although LHA neurons innervate adipose tissues, the identity of neurons that regulate fat is undefined. Here we show that GABRA5-positive neurons in LHA (GABRA5LHA) polysynaptically project to brown and white adipose tissues in the periphery. GABRA5LHA are a distinct subpopulation of GABAergic neurons and show decreased pacemaker firing in diet-induced obesity mouse models in males. Chemogenetic inhibition of GABRA5LHA suppresses fat thermogenesis and increases weight gain, whereas gene silencing of GABRA5 in LHA decreases weight gain. In the diet-induced obesity mouse model, GABRA5LHA are tonically inhibited by nearby reactive astrocytes releasing GABA, which is synthesized by monoamine oxidase B (Maob). Gene silencing of astrocytic Maob in LHA facilitates fat thermogenesis and reduces weight gain significantly without affecting food intake, which is recapitulated by administration of a Maob inhibitor, KDS2010. We propose that firing of GABRA5LHA suppresses fat accumulation and selective inhibition of astrocytic GABA is a molecular target for treating obesity.
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Affiliation(s)
- Moonsun Sa
- Center for Cognition and Sociality, Institute for Basic Science, Daejeon, Republic of Korea
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seongbuk-gu, Seoul, Republic of Korea
| | - Eun-Seon Yoo
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon, Republic of Korea
| | - Wuhyun Koh
- Center for Cognition and Sociality, Institute for Basic Science, Daejeon, Republic of Korea
| | - Mingu Gordon Park
- Center for Cognition and Sociality, Institute for Basic Science, Daejeon, Republic of Korea
| | - Hyun-Jun Jang
- Ulsan National Institute of Science and Technology, Ulsan, Republic of Korea
| | - Yong Ryoul Yang
- Ulsan National Institute of Science and Technology, Ulsan, Republic of Korea
| | - Mridula Bhalla
- Center for Cognition and Sociality, Institute for Basic Science, Daejeon, Republic of Korea
- IBS School, University of Science and Technology, Daejeon, Republic of Korea
| | - Jae-Hun Lee
- Center for Cognition and Sociality, Institute for Basic Science, Daejeon, Republic of Korea
| | - Jiwoon Lim
- Center for Cognition and Sociality, Institute for Basic Science, Daejeon, Republic of Korea
- IBS School, University of Science and Technology, Daejeon, Republic of Korea
| | - Woojin Won
- Center for Cognition and Sociality, Institute for Basic Science, Daejeon, Republic of Korea
| | - Jea Kwon
- Center for Cognition and Sociality, Institute for Basic Science, Daejeon, Republic of Korea
| | - Joon-Ho Kwon
- Center for Cognition and Sociality, Institute for Basic Science, Daejeon, Republic of Korea
| | - Yejin Seong
- Center for Cognition and Sociality, Institute for Basic Science, Daejeon, Republic of Korea
| | - Byungeun Kim
- Center for Brain Disorders, Brain Science Institute, Korea Institute of Science and Technology, Seoul, Republic of Korea
- Division of Bio-Medical Science and Technology, University of Science and Technology, Daejeon, Republic of Korea
| | - Heeyoung An
- Center for Cognition and Sociality, Institute for Basic Science, Daejeon, Republic of Korea
| | - Seung Eun Lee
- Virus Facility, Research Animal Resource Center, Korea Institute of Science and Technology, Seoul, Republic of Korea
| | - Ki Duk Park
- Center for Brain Disorders, Brain Science Institute, Korea Institute of Science and Technology, Seoul, Republic of Korea
- Division of Bio-Medical Science and Technology, University of Science and Technology, Daejeon, Republic of Korea
| | - Pann-Ghill Suh
- Ulsan National Institute of Science and Technology, Ulsan, Republic of Korea
| | - Jong-Woo Sohn
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon, Republic of Korea
| | - C Justin Lee
- Center for Cognition and Sociality, Institute for Basic Science, Daejeon, Republic of Korea.
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seongbuk-gu, Seoul, Republic of Korea.
- IBS School, University of Science and Technology, Daejeon, Republic of Korea.
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Silva MSB, Campbell RE. Polycystic Ovary Syndrome and the Neuroendocrine Consequences of Androgen Excess. Compr Physiol 2022; 12:3347-3369. [PMID: 35578968 DOI: 10.1002/cphy.c210025] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Polycystic ovary syndrome (PCOS) is a major endocrine disorder strongly associated with androgen excess and frequently leading to female infertility. Although classically considered an ovarian disease, altered neuroendocrine control of gonadotropin-releasing hormone (GnRH) neurons in the brain and abnormal gonadotropin secretion may underpin PCOS presentation. Defective regulation of GnRH pulse generation in PCOS promotes high luteinizing hormone (LH) pulsatile secretion, which in turn overstimulates ovarian androgen production. Early and emerging evidence from preclinical models suggests that maternal androgen excess programs abnormalities in developing neuroendocrine circuits that are associated with PCOS pathology, and that these abnormalities are sustained by postpubertal elevation of endogenous androgen levels. This article will discuss experimental evidence, from the clinic and in preclinical animal models, that has significantly contributed to our understanding of how androgen excess influences the assembly and maintenance of neuroendocrine impairments in the female brain. Abnormal central gamma-aminobutyric acid (GABA) signaling has been identified in both patients and preclinical models as a possible link between androgen excess and elevated GnRH/LH secretion. Enhanced GABAergic innervation and drive to GnRH neurons is suspected to contribute to the pathogenesis and early manifestation of neuroendocrine derangement in PCOS. Accordingly, this article also provides an overview of GABA regulation of GnRH neuron function from prenatal development to adulthood to discuss possible avenues for future discovery research and therapeutic interventions. © 2022 American Physiological Society. Compr Physiol 12:3347-3369, 2022.
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Affiliation(s)
- Mauro S B Silva
- Department of Medicine, Division of Endocrinology, Diabetes and Hypertension, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
| | - Rebecca E Campbell
- Centre for Neuroendocrinology, Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
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Bhattarai P, Rijal S, Bhattarai JP, Cho DH, Han SK. Suppression of neurotransmission on gonadotropin-releasing hormone neurons in letrozole-induced polycystic ovary syndrome: A mouse model. Front Endocrinol (Lausanne) 2022; 13:1059255. [PMID: 36699037 PMCID: PMC9868609 DOI: 10.3389/fendo.2022.1059255] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/01/2022] [Accepted: 12/08/2022] [Indexed: 01/11/2023] Open
Abstract
OBJECTIVE Polycystic ovarian syndrome (PCOS) is a heterogeneous endocrine disorder in reproductive-age women, characterized by the accretion of small cystic follicles in the ovary associated with chronic anovulation and overproduction of androgens. Ovarian function in all mammals is controlled by gonadotropin-releasing hormone (GnRH) neurons, which are the central regulator of the hypothalamic-pituitary-gonadal (HPG) axis. However, the impact on the neurotransmitter system regulating GnRH neuronal function in the letrozole-induced PCOS mouse model remains unclear. METHODS In this study, we compared the response of various neurotransmitters and neurosteroids regulating GnRH neuronal activities between letrozole-induced PCOS and normal mice via electrophysiological techniques. RESULTS Response to neurotransmitter systems like GABAergic, glutamatergic and kisspeptinergic were suppressed in letrozole-fed compared to normal mice. In addition, neurosteroids tetrahydrodeoxycorticosterone (THDOC) and 4,5,6,7-tetrahydroisoxazolo[5,4-c] pyridine-3-ol (THIP) mediated response on GnRH neurons were significantly smaller on letrozole-fed mice compared to normal mice. Furthermore, we also found that letrozole-fed mice showed irregularity in the estrous cycle, increased body weight, and anovulation in female mice. CONCLUSION These findings suggest that PCOS is an endocrine disorder that may directly affect the neurotransmitter system regulating GnRH neuronal activity at the hypothalamic level and impact reproductive physiology.
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Affiliation(s)
- Pravin Bhattarai
- Department of Oral Physiology, School of Dentistry and Institute of Oral Bioscience, Jeonbuk National University, Jeonju, South Korea
| | - Santosh Rijal
- Department of Oral Physiology, School of Dentistry and Institute of Oral Bioscience, Jeonbuk National University, Jeonju, South Korea
| | - Janardhan P. Bhattarai
- Department of Neuroscience, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, United States
| | - Dong Hyu Cho
- Department of Obstetrics and Gynecology, Jeonbuk National University Medical School, Research Institute of Clinical Medicine of Jeonbuk National University-Biomedical Research Institute of Jeonbuk National University Hospital, Jeonju, South Korea
- *Correspondence: Dong Hyu Cho, ; Seong Kyu Han,
| | - Seong Kyu Han
- Department of Oral Physiology, School of Dentistry and Institute of Oral Bioscience, Jeonbuk National University, Jeonju, South Korea
- *Correspondence: Dong Hyu Cho, ; Seong Kyu Han,
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Martynyuk AE, Ju LS, Morey TE. The potential role of stress and sex steroids in heritable effects of sevoflurane. Biol Reprod 2021; 105:735-746. [PMID: 34192761 DOI: 10.1093/biolre/ioab129] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Revised: 03/17/2021] [Accepted: 06/25/2021] [Indexed: 12/11/2022] Open
Abstract
Most surgical procedures require general anesthesia, which is a reversible deep sedation state lacking all perception. The induction of this state is possible because of complex molecular and neuronal network actions of general anesthetics (GAs) and other pharmacological agents. Laboratory and clinical studies indicate that the effects of GAs may not be completely reversible upon anesthesia withdrawal. The long-term neurocognitive effects of GAs, especially when administered at the extremes of ages, are an increasingly recognized health concern and the subject of extensive laboratory and clinical research. Initial studies in rodents suggest that the adverse effects of GAs, whose actions involve enhancement of GABA type A receptor activity (GABAergic GAs), can also extend to future unexposed offspring. Importantly, experimental findings show that GABAergic GAs may induce heritable effects when administered from the early postnatal period to at least young adulthood, covering nearly all age groups that may have children after exposure to anesthesia. More studies are needed to understand when and how the clinical use of GAs in a large and growing population of patients can result in lower resilience to diseases in the even larger population of their unexposed offspring. This minireview is focused on the authors' published results and data in the literature supporting the notion that GABAergic GAs, in particular sevoflurane, may upregulate systemic levels of stress and sex steroids and alter expressions of genes that are essential for the functioning of these steroid systems. The authors hypothesize that stress and sex steroids are involved in the mediation of sex-specific heritable effects of sevoflurane.
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Affiliation(s)
- Anatoly E Martynyuk
- Department of Anesthesiology, University of Florida College of Medicine, Gainesville, FL, USA.,McKnight Brain Institute, University of Florida College of Medicine, Gainesville, FL, USA
| | - Ling-Sha Ju
- Department of Anesthesiology, University of Florida College of Medicine, Gainesville, FL, USA
| | - Timothy E Morey
- Department of Anesthesiology, University of Florida College of Medicine, Gainesville, FL, USA
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Freitag FB, Ahemaiti A, Jakobsson JET, Weman HM, Lagerström MC. Spinal gastrin releasing peptide receptor expressing interneurons are controlled by local phasic and tonic inhibition. Sci Rep 2019; 9:16573. [PMID: 31719558 PMCID: PMC6851355 DOI: 10.1038/s41598-019-52642-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Accepted: 10/18/2019] [Indexed: 11/09/2022] Open
Abstract
Dorsal horn gastrin-releasing peptide receptor (GRPR) neurons have a central role in itch transmission. Itch signaling has been suggested to be controlled by an inhibitory network in the spinal dorsal horn, as increased scratching behavior can be induced by pharmacological disinhibition or ablation of inhibitory interneurons, but the direct influence of the inhibitory tone on the GRPR neurons in the itch pathway have not been explored. Here we have investigated spinal GRPR neurons through in vitro and bioinformatical analysis. Electrophysiological recordings revealed that GRPR neurons receive local spontaneous excitatory inputs transmitted by glutamate and inhibitory inputs by glycine and GABA, which were transmitted either by separate glycinergic and GABAergic synapses or by glycine and GABA co-releasing synapses. Additionally, all GRPR neurons received both glycine- and GABA-induced tonic currents. The findings show a complex inhibitory network, composed of synaptic and tonic currents that gates the excitability of GRPR neurons, which provides direct evidence for the existence of an inhibitory tone controlling spontaneous discharge in an itch-related neuronal network in the spinal cord. Finally, calcium imaging revealed increased levels of neuronal activity in Grpr-Cre neurons upon application of somatostatin, which provides direct in vitro evidence for disinhibition of these dorsal horn interneurons.
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Affiliation(s)
- Fabio B Freitag
- Department of Neuroscience, Uppsala University, Uppsala, Sweden
| | | | | | - Hannah M Weman
- Department of Neuroscience, Uppsala University, Uppsala, Sweden
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Does kisspeptin participate in GABA-mediated modulation of GnRH and GnRH receptor biosynthesis in the hypothalamic-pituitary unit of follicular-phase ewes? Pharmacol Rep 2019; 71:636-643. [PMID: 31176893 DOI: 10.1016/j.pharep.2019.02.019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Revised: 02/25/2019] [Accepted: 02/28/2019] [Indexed: 11/24/2022]
Abstract
BACKGROUND The inverse relationship between GnRH transcript level and GABA neurons activity has suggested that GABA at the hypothalamic level may exert a suppressive effect on subsequent steps of the GnRH biosynthesis. In the present study, we analyzed the effects of GABA type A receptor agonist (muscimol) or antagonist (bicuculline) on molecular mechanisms governing GnRH/LH secretion in follicular-phase sheep. METHODS ELISA technique was used to investigate the effects of muscimol and/or bicuculline on levels of post-translational products of genes encoding GnRH ligand and GnRH receptor (GnRHR) in the preoptic area (POA), anterior (AH) and ventromedial (VMH) hypothalamus, stalk/median eminence (SME), and GnRHR in the anterior pituitary (AP). Real-time PCR was chosen for determination of the effect of drugs on kisspeptin (Kiss 1) mRNA level in POA and VMH including arcuate nucleus (VMH/ARC), and on Kiss1 receptor (Kiss1r) mRNA abundance in POA-hypothalamic structures. These analyses were supplemented by RIA method for measurement of plasma LH concentration. RESULTS The study demonstrated that muscimol and bicuculline significantly decreased or increased GnRH biosynthesis in all analyzed structures, respectively, and led to analogous changes in plasma LH concentration. Similar muscimol- and bicuculline-related alterations were observed in levels of GnRHR. However, the expression of Kiss 1 and Kiss1r mRNAs in selected POA-hypothalamic areas of either muscimol- and bicuculline-treated animals remained unaltered. CONCLUSIONS Our data suggest that GABAergic neurotransmission is involved in the regulatory pathways of GnRH/GnRHR biosynthesis and then GnRH/LH release in follicular-phase sheep conceivably via indirect mechanisms that exclude involvement of Kiss 1 neurons.
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Spergel DJ. Modulation of Gonadotropin-Releasing Hormone Neuron Activity and Secretion in Mice by Non-peptide Neurotransmitters, Gasotransmitters, and Gliotransmitters. Front Endocrinol (Lausanne) 2019; 10:329. [PMID: 31178828 PMCID: PMC6538683 DOI: 10.3389/fendo.2019.00329] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2019] [Accepted: 05/07/2019] [Indexed: 12/18/2022] Open
Abstract
Gonadotropin-releasing hormone (GnRH) neuron activity and GnRH secretion are essential for fertility in mammals. Here, I review findings from mouse studies on the direct modulation of GnRH neuron activity and GnRH secretion by non-peptide neurotransmitters (GABA, glutamate, dopamine, serotonin, norepinephrine, epinephrine, histamine, ATP, adenosine, and acetylcholine), gasotransmitters (nitric oxide and carbon monoxide), and gliotransmitters (prostaglandin E2 and possibly GABA, glutamate, and ATP). These neurotransmitters, gasotransmitters, and gliotransmitters have been shown to directly modulate activity and/or GnRH secretion in GnRH neurons in vivo or ex vivo (brain slices), from postnatal through adult mice, or in embryonic or immortalized mouse GnRH neurons. However, except for GABA, nitric oxide, and prostaglandin E2, which appear to be essential for normal GnRH neuron activity, GnRH secretion, and fertility in males and/or females, the biological significance of their direct modulation of GnRH neuron activity and/or GnRH secretion in the central regulation of reproduction remains largely unknown and requires further exploration.
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Melón LC, Nolan ZT, Colar D, Moore EM, Boehm SL. Activation of extrasynaptic δ-GABA A receptors globally or within the posterior-VTA has estrous-dependent effects on consumption of alcohol and estrous-independent effects on locomotion. Horm Behav 2017; 95:65-75. [PMID: 28765080 PMCID: PMC5623082 DOI: 10.1016/j.yhbeh.2017.07.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2016] [Revised: 07/26/2017] [Accepted: 07/26/2017] [Indexed: 11/21/2022]
Abstract
Recent reports support higher than expected rates of binge alcohol consumption among women and girls. Unfortunately, few studies have assessed the mechanisms underlying this pattern of intake in females. Studies in males suggest that alcohol concentrations relevant to the beginning stages of binge intoxication may selectively target tonic GABAergic inhibition mediated by GABAA receptor subtypes expressing the δ-subunit protein (δ-GABAARs). Indeed, administration of agonists that interact with these δ-GABAARs prior to alcohol access can abolish binge drinking behavior in male mice. These δ-GABAARs have also been shown to exhibit estrous-dependent plasticity in regions relevant to drug taking behavior, like the hippocampus and periaqueductal gray. The present experiments were designed to determine whether the estrous cycle would alter binge drinking, or our ability to modulate this pattern of alcohol use with THIP, an agonist with high selectivity and efficacy at δ-GABAARs. Using the Drinking-in-the-Dark (DID) binge-drinking model, regularly cycling female mice were given 2h of daily access to alcohol (20%v/v). Vaginal cytology or vaginal impedance was assessed after drinking sessions to track estrous status. There was no fluctuation in binge drinking associated with the estrous cycle. Both Intra-posterior-VTA administration of THIP and systemic administration of the drug was also associated with an estrous cycle dependent reduction in drinking behavior. Pre-treatment with finasteride to inhibit synthesis of 5α-reduced neurosteroids did not disrupt THIP's effects. Analysis of δ-subunit mRNA from posterior-VTA enriched tissue samples revealed that expression of this GABAA receptor subunit is elevated during diestrus in this region. Taken together, these studies demonstrate that δGABAARs in the VTA are an important target for binge drinking in females and confirm that the estrous cycle is an important moderator of the pharmacology of this GABAA receptor subtype.
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Affiliation(s)
- Laverne C Melón
- Addiction Neuroscience, Department of Psychology, Indiana University/Purdue University-Indianapolis, Indianapolis, IN 46202, USA; Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111, USA
| | | | - Delphine Colar
- Addiction Neuroscience, Department of Psychology, Indiana University/Purdue University-Indianapolis, Indianapolis, IN 46202, USA
| | - Eileen M Moore
- Center for Behavioral Teratology, Department of Psychology, San Diego State University, San Diego, CA 92120, USA
| | - Stephen L Boehm
- Addiction Neuroscience, Department of Psychology, Indiana University/Purdue University-Indianapolis, Indianapolis, IN 46202, USA.
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Pinson A, Franssen D, Gérard A, Parent AS, Bourguignon JP. Neuroendocrine disruption without direct endocrine mode of action: Polychloro-biphenyls (PCBs) and bisphenol A (BPA) as case studies. C R Biol 2017; 340:432-438. [PMID: 28826787 DOI: 10.1016/j.crvi.2017.07.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Accepted: 07/21/2017] [Indexed: 11/26/2022]
Abstract
Endocrine disruption is commonly thought to be restricted to a direct endocrine mode of action i.e. the perturbation of the activation of a given type of hormonal receptor by its natural ligand. Consistent with the WHO definition of an endocrine disrupter, a key issue is the "altered function(s) of the endocrine system". Such altered functions can result from different chemical interactions, beyond agonistic or antagonistic effect at a given receptor. Based on neuroendocrine disruption by polychlorinated biphenyls and bisphenol A, this paper proposes different mechanistic paradigms that can result in adverse health effects. They are a consequence of altered endocrine function(s) secondary to chemical interaction with different steps in the physiological regulatory processes, thus accounting for a possibly indirect endocrine mode of action.
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Affiliation(s)
- Anneline Pinson
- Developmental Neuroendocrinology unit, GIGA Neurosciences, University of Liège, Quartier Hôpital, Tour 4, 1(er) étage, avenue Hippocrate 15, 4000 Liège, Belgium
| | - Delphine Franssen
- Developmental Neuroendocrinology unit, GIGA Neurosciences, University of Liège, Quartier Hôpital, Tour 4, 1(er) étage, avenue Hippocrate 15, 4000 Liège, Belgium
| | - Arlette Gérard
- Developmental Neuroendocrinology unit, GIGA Neurosciences, University of Liège, Quartier Hôpital, Tour 4, 1(er) étage, avenue Hippocrate 15, 4000 Liège, Belgium
| | - Anne-Simone Parent
- Developmental Neuroendocrinology unit, GIGA Neurosciences, University of Liège, Quartier Hôpital, Tour 4, 1(er) étage, avenue Hippocrate 15, 4000 Liège, Belgium
| | - Jean-Pierre Bourguignon
- Developmental Neuroendocrinology unit, GIGA Neurosciences, University of Liège, Quartier Hôpital, Tour 4, 1(er) étage, avenue Hippocrate 15, 4000 Liège, Belgium.
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Kanasaki H, Oride A, Mijiddorj T, Sukhbaatar U, Kyo S. How is GnRH regulated in GnRH-producing neurons? Studies using GT1-7 cells as a GnRH-producing cell model. Gen Comp Endocrinol 2017; 247:138-142. [PMID: 28131616 DOI: 10.1016/j.ygcen.2017.01.025] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2016] [Revised: 01/05/2017] [Accepted: 01/23/2017] [Indexed: 12/24/2022]
Abstract
Hypothalamic secretion of gonadotropin-releasing hormone (GnRH) has been established as a principle pathway for initiating and integrating female reproductive function. GnRH stimulates the release of two gonadotropins-luteinizing hormone and follicle-stimulating hormone-from the anterior pituitary, which eventually stimulate the synthesis of sex steroids in association with follicular growth and ovulation. This reproductive control of the hypothalamic-pituitary-gonadal (HPG) axis also mediates gonadal feedback mechanisms. Although GnRH neurons certainly play a pivotal role in the HPG axis, the detailed mechanisms of their functional network, including regulatory systems, remain unknown. After the discovery of the indispensable role of kisspeptin in the development of human reproductive functions, our understanding of the neuroendocrine regulation of the HPG axis was revolutionized, and it is now recognized that kisspeptin acts upstream of GnRH and is responsible for sex steroid feedback mechanisms. Kisspeptin can stimulate gonadotropin release from the pituitary gland by stimulating GnRH release and GnRH antagonists prevent kisspeptin-induced gonadotropin release. Furthermore, it has been shown that GnRH neurons express kisspeptin receptors. Nevertheless, the detailed mechanisms underlying the regulation of homogeneous populations of GnRH neurons are still largely unknown because of the limitations of experimental models used for investigation. The hypothalamus consists of a complex network of distinct neuronal cells, and it is difficult to isolate single-cell populations of GnRH neurons. The establishment of GnRH-expressing cell lines has allowed us to examine the events happening at the single-cell level. In this review, we describe in vitro studies using a GnRH-producing cell model, GT1-7 cells, which have been used to examine how GnRH-producing cells respond to hypothalamic factors and how they are involved in GnRH synthesis.
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Affiliation(s)
- Haruhiko Kanasaki
- Department of Obstetrics and Gynecology, Shimane University Faculty of Medicine, Izumo 693-8501, Japan.
| | - Aki Oride
- Department of Obstetrics and Gynecology, Shimane University Faculty of Medicine, Izumo 693-8501, Japan
| | - Tselmeg Mijiddorj
- Department of Obstetrics and Gynecology, Shimane University Faculty of Medicine, Izumo 693-8501, Japan
| | - Unurjargal Sukhbaatar
- Department of Obstetrics and Gynecology, Shimane University Faculty of Medicine, Izumo 693-8501, Japan
| | - Satoru Kyo
- Department of Obstetrics and Gynecology, Shimane University Faculty of Medicine, Izumo 693-8501, Japan
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Kim MJ, Park YH, Yang KY, Ju JS, Bae YC, Han SK, Ahn DK. Participation of central GABA A receptors in the trigeminal processing of mechanical allodynia in rats. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2016; 21:65-74. [PMID: 28066142 PMCID: PMC5214912 DOI: 10.4196/kjpp.2017.21.1.65] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Revised: 10/12/2016] [Accepted: 10/13/2016] [Indexed: 01/28/2023]
Abstract
Here we investigated the central processing mechanisms of mechanical allodynia and found a direct excitatory link with low-threshold input to nociceptive neurons. Experiments were performed on male Sprague-Dawley rats weighing 230-280 g. Subcutaneous injection of interleukin 1 beta (IL-1β) (1 ng/10 µL) was used to produce mechanical allodynia and thermal hyperalgesia. Intracisternal administration of bicuculline, a gamma aminobutyric acid A (GABAA) receptor antagonist, produced mechanical allodynia in the orofacial area under normal conditions. However, intracisternal administration of bicuculline (50 ng) produced a paradoxical anti-allodynic effect under inflammatory pain conditions. Pretreatment with resiniferatoxin (RTX), which depletes capsaicin receptor protein in primary afferent fibers, did not alter the paradoxical anti-allodynic effects produced by the intracisternal injection of bicuculline. Intracisternal injection of bumetanide, an Na-K-Cl cotransporter (NKCC 1) inhibitor, reversed the IL-1β-induced mechanical allodynia. In the control group, application of GABA (100 µM) or muscimol (3 µM) led to membrane hyperpolarization in gramicidin perforated current clamp mode. However, in some neurons, application of GABA or muscimol led to membrane depolarization in the IL-1β-treated rats. These results suggest that some large myelinated Aβ fibers gain access to the nociceptive system and elicit pain sensation via GABAA receptors under inflammatory pain conditions.
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Affiliation(s)
- Min Ji Kim
- Department of Oral Physiology, School of Dentistry, Kyungpook National University, Daegu 41940, Korea
| | - Young Hong Park
- Department of Oral Physiology, School of Dentistry, Kyungpook National University, Daegu 41940, Korea
| | - Kui Ye Yang
- Department of Oral Physiology, School of Dentistry, Kyungpook National University, Daegu 41940, Korea
| | - Jin Sook Ju
- Department of Oral Physiology, School of Dentistry, Kyungpook National University, Daegu 41940, Korea
| | - Yong Chul Bae
- Department of Oral Anatomy, School of Dentistry, Kyungpook National University, Daegu 41940, Korea
| | - Seong Kyu Han
- Department of Oral Physiology, School of Dentistry and Institute of Oral Bioscience, Chonbuk National University, Jeonju 54896, Korea
| | - Dong Kuk Ahn
- Department of Oral Physiology, School of Dentistry, Kyungpook National University, Daegu 41940, Korea
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Spool JA, Stevenson SA, Angyal CS, Riters LV. Contributions of testosterone and territory ownership to sexually-motivated behaviors and mRNA expression in the medial preoptic area of male European starlings. Horm Behav 2016; 86:36-44. [PMID: 27633459 PMCID: PMC5159298 DOI: 10.1016/j.yhbeh.2016.09.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Revised: 09/07/2016] [Accepted: 09/10/2016] [Indexed: 12/16/2022]
Abstract
Animals integrate social information with their internal endocrine state to control the timing of behavior, but how these signals are integrated in the brain is not understood. The medial preoptic area (mPOA) may play an integrative role in the control of courtship behavior, as it receives projections from multiple sensory systems, and is central to the hormonal control of courtship behavior across vertebrates. Additionally, data from many species implicate opioid and dopaminergic systems in the mPOA in the control of male courtship behavior. We used European starlings to test the hypothesis that testosterone (T) and social status (in the form of territory possession) interact to control the timing of courtship behavior by modulating steroid hormone-, opioid- and dopaminergic-related gene expression in the mPOA. We found that only males given both T and a nesting territory produced high rates of courtship behavior in response to a female. T treatment altered patterns of gene expression in the mPOA by increasing androgen receptor, aromatase, mu-opioid receptor and preproenkephalin mRNA and decreasing tyrosine hydroxylase mRNA expression. Territory possession did not alter mRNA expression in the mPOA, despite the finding that only birds with both T and a nesting territory produced courtship behavior. We propose that T prepares the mPOA to respond to the presence of a female with high rates of courtship song by altering gene expression, but that activity in the mPOA is under a continuous (i.e. tonic) inhibition until a male starling obtains a nesting territory.
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MESH Headings
- Animals
- Courtship
- Dopamine/genetics
- Dopamine/metabolism
- Female
- Gene Expression Regulation
- Male
- Motivation/physiology
- Preoptic Area/metabolism
- RNA, Messenger/metabolism
- Receptors, Androgen/genetics
- Receptors, Androgen/metabolism
- Receptors, Dopamine/genetics
- Receptors, Dopamine/metabolism
- Receptors, Estrogen/genetics
- Receptors, Estrogen/metabolism
- Receptors, Opioid, mu/genetics
- Receptors, Opioid, mu/metabolism
- Sexual Behavior, Animal/physiology
- Starlings/blood
- Starlings/genetics
- Starlings/physiology
- Territoriality
- Testosterone/blood
- Testosterone/physiology
- Vocalization, Animal/physiology
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Affiliation(s)
- Jeremy A Spool
- Department of Zoology, 430 Lincoln Drive, University of Wisconsin, Madison, WI 53706, USA.
| | - Sharon A Stevenson
- Department of Zoology, 430 Lincoln Drive, University of Wisconsin, Madison, WI 53706, USA.
| | - Caroline S Angyal
- Department of Zoology, 430 Lincoln Drive, University of Wisconsin, Madison, WI 53706, USA.
| | - Lauren V Riters
- Department of Zoology, 430 Lincoln Drive, University of Wisconsin, Madison, WI 53706, USA.
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13
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Farkas I, Vastagh C, Farkas E, Bálint F, Skrapits K, Hrabovszky E, Fekete C, Liposits Z. Glucagon-Like Peptide-1 Excites Firing and Increases GABAergic Miniature Postsynaptic Currents (mPSCs) in Gonadotropin-Releasing Hormone (GnRH) Neurons of the Male Mice via Activation of Nitric Oxide (NO) and Suppression of Endocannabinoid Signaling Pathways. Front Cell Neurosci 2016; 10:214. [PMID: 27672360 PMCID: PMC5018486 DOI: 10.3389/fncel.2016.00214] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2016] [Accepted: 08/26/2016] [Indexed: 12/25/2022] Open
Abstract
Glucagon-like peptide-1 (GLP-1), a metabolic signal molecule, regulates reproduction, although, the involved molecular mechanisms have not been elucidated, yet. Therefore, responsiveness of gonadotropin-releasing hormone (GnRH) neurons to the GLP-1 analog Exendin-4 and elucidation of molecular pathways acting downstream to the GLP-1 receptor (GLP-1R) have been challenged. Loose patch-clamp recordings revealed that Exendin-4 (100 nM-5 μM) elevated firing rate in hypothalamic GnRH-GFP neurons of male mice via activation of GLP-1R. Whole-cell patch-clamp measurements demonstrated increased excitatory GABAergic miniature postsynaptic currents (mPSCs) frequency after Exendin-4 administration, which was eliminated by the GLP-1R antagonist Exendin-3(9-39) (1 μM). Intracellular application of the G-protein inhibitor GDP-β-S (2 mM) impeded action of Exendin-4 on mPSCs, suggesting direct excitatory action of GLP-1 on GnRH neurons. Blockade of nitric-oxide (NO) synthesis by Nω-Nitro-L-arginine methyl ester hydrochloride (L-NAME; 100 μM) or N(5)-[Imino(propylamino)methyl]-L-ornithine hydrochloride (NPLA; 1 μM) or intracellular scavenging of NO by 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (CPTIO; 1 mM) partially attenuated the excitatory effect of Exendin-4. Similar partial inhibition was achieved by hindering endocannabinoid pathway using cannabinoid receptor type-1 (CB1) inverse-agonist 1-(2,4-dichlorophenyl)-5-(4-iodophenyl)-4-methyl-N-(1-piperidyl) pyrazole-3-carboxamide (AM251; 1 μM). Simultaneous blockade of NO and endocannabinoid signaling mechanisms eliminated action of Exendin-4 suggesting involvement of both retrograde machineries. Intracellular application of the transient receptor potential vanilloid 1 (TRPV1)-antagonist 2E-N-(2, 3-Dihydro-1,4-benzodioxin-6-yl)-3-[4-(1, 1-dimethylethyl)phenyl]-2-Propenamide (AMG9810; 10 μM) or the fatty acid amide hydrolase (FAAH)-inhibitor PF3845 (5 μM) impeded the GLP-1-triggered endocannabinoid pathway indicating an anandamide-TRPV1-sensitive control of 2-arachidonoylglycerol (2-AG) production. Furthermore, GLP-1 immunoreactive (IR) axons innervated GnRH neurons in the hypothalamus suggesting that GLP-1 of both peripheral and neuronal sources can modulate GnRH neurons. RT-qPCR study confirmed the expression of GLP-1R and neuronal NO synthase (nNOS) mRNAs in GnRH-GFP neurons. Immuno-electron microscopic analysis revealed the presence of nNOS protein in GnRH neurons. These results indicate that GLP-1 exerts direct facilitatory actions via GLP-1R on GnRH neurons and modulates NO and 2-AG retrograde signaling mechanisms that control the presynaptic excitatory GABAergic inputs to GnRH neurons.
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Affiliation(s)
- Imre Farkas
- Laboratory of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences Budapest, Hungary
| | - Csaba Vastagh
- Laboratory of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences Budapest, Hungary
| | - Erzsébet Farkas
- Laboratory of Integrative Neuroendocrinology, Institute of Experimental Medicine, Hungarian Academy of SciencesBudapest, Hungary; Roska Tamás Doctoral School of Sciences and Technology, Faculty of Information Technology and Bionics, Pázmány Péter Catholic UniversityBudapest, Hungary
| | - Flóra Bálint
- Laboratory of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of SciencesBudapest, Hungary; Roska Tamás Doctoral School of Sciences and Technology, Faculty of Information Technology and Bionics, Pázmány Péter Catholic UniversityBudapest, Hungary
| | - Katalin Skrapits
- Laboratory of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences Budapest, Hungary
| | - Erik Hrabovszky
- Laboratory of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences Budapest, Hungary
| | - Csaba Fekete
- Laboratory of Integrative Neuroendocrinology, Institute of Experimental Medicine, Hungarian Academy of SciencesBudapest, Hungary; Department of Medicine, Division of Endocrinology, Diabetes and Metabolism, Tupper Research Institute, Tufts Medical CenterBoston, MA, USA
| | - Zsolt Liposits
- Laboratory of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of SciencesBudapest, Hungary; Department of Neuroscience, Faculty of Information Technology and Bionics, Pázmány Péter Catholic UniversityBudapest, Hungary
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14
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Camille Melón L, Maguire J. GABAergic regulation of the HPA and HPG axes and the impact of stress on reproductive function. J Steroid Biochem Mol Biol 2016; 160:196-203. [PMID: 26690789 PMCID: PMC4861672 DOI: 10.1016/j.jsbmb.2015.11.019] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Revised: 11/16/2015] [Accepted: 11/26/2015] [Indexed: 11/25/2022]
Abstract
The hypothalamic-pituitary-adrenal (HPA) and hypothalamic-pituitary-gonadal (HPG) axes are regulated by GABAergic signaling at the level of corticotropin-releasing hormone (CRH) and gonadotropin-releasing hormone (GnRH) neurons, respectively. Under basal conditions, activity of CRH and GnRH neurons are controlled in part by both phasic and tonic GABAergic inhibition, mediated by synaptic and extrasynaptic GABAA receptors (GABAARs), respectively. For CRH neurons, this tonic GABAergic inhibition is mediated by extrasynaptic, δ subunit-containing GABAARs. Similarly, a THIP-sensitive tonic GABAergic current has been shown to regulate GnRH neurons, suggesting a role for δ subunit-containing GABAARs; however, this remains to be explicitly demonstrated. GABAARs incorporating the δ subunit confer neurosteroid sensitivity, suggesting a potential role for neurosteroid modulation in the regulation of the HPA and HPG axes. Thus, stress-derived neurosteroids may contribute to the impact of stress on reproductive function. Interestingly, excitatory actions of GABA have been demonstrated in both CRH neurons at the apex of control of the HPA axis and in GnRH neurons which mediate the HPG axis, adding to the complexity for the role of GABAergic signaling in the regulation of these systems. Here we review the effects that stress has on GnRH neurons and HPG axis function alongside evidence supporting GABAARs as a major interface between the stress and reproductive axes.
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Affiliation(s)
- Laverne Camille Melón
- Tufts University School of Medicine, Department of Neuroscience, Boston, MA 02111, United States
| | - Jamie Maguire
- Tufts University School of Medicine, Department of Neuroscience, Boston, MA 02111, United States.
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15
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Franssen D, Gérard A, Hennuy B, Donneau AF, Bourguignon JP, Parent AS. Delayed Neuroendocrine Sexual Maturation in Female Rats After a Very Low Dose of Bisphenol A Through Altered GABAergic Neurotransmission and Opposing Effects of a High Dose. Endocrinology 2016; 157:1740-50. [PMID: 26950200 DOI: 10.1210/en.2015-1937] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Rat sexual maturation is preceded by a reduction of the interpulse interval (IPI) of GnRH neurosecretion. This work aims at studying disruption of that neuroendocrine event in females after early exposure to a very low dose of bisphenol A (BPA), a ubiquitous endocrine disrupting chemical. Female rats were exposed to vehicle or BPA 25 ng/kg·d, 25 μg/kg·d, or 5 mg/kg·d from postnatal day (PND)1 to PND5 or PND15. Exposure to 25 ng/kg·d of BPA for 5 or 15 days was followed by a delay in developmental reduction of GnRH IPI studied ex vivo on PND20. After 15 days of exposure to that low dose of BPA, vaginal opening tended to be delayed. In contrast, exposure to BPA 5 mg/kg·d for 15 days resulted in a premature reduction in GnRH IPI and a trend toward early vaginal opening. RNA sequencing analysis on PND20 indicated that exposure to BPA resulted in opposing dose effects on the mRNA expression of hypothalamic genes involved in gamma aminobutyric acid A (GABAA) neurotransmission. The study of GnRH secretion in vitro in the presence of GABAA receptor agonist/antagonist confirmed an increased or a reduced GABAergic tone after in vivo exposure to the very low or the high dose of BPA, respectively. Overall, we show for the first time that neonatal exposure to BPA leads to opposing dose-dependent effects on the neuroendocrine control of puberty in the female rat. A very low and environmentally relevant dose of BPA delays neuroendocrine maturation related to puberty through increased inhibitory GABAergic neurotransmission.
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Affiliation(s)
- Delphine Franssen
- Neuroendocrinology Unit (D.F., A.G., J.-P.B., A.-S.P.), Interdisciplinary Cluster for Applied Genoproteomics Neurosciences; Interdisciplinary Cluster for Applied Genoproteomics Transcriptomic Platform (B.H.); and Department of Public Health (A.-F.D.), Biostatistics Unit, University of Liège, Sart-Tilman, B-4000 Liège, Belgium; and Department of Pediatrics (A.G., J.-P.B., A.-S.P.), Centre Hospitalier Universitaire de Liège, B-4032 Chênée, Belgium
| | - Arlette Gérard
- Neuroendocrinology Unit (D.F., A.G., J.-P.B., A.-S.P.), Interdisciplinary Cluster for Applied Genoproteomics Neurosciences; Interdisciplinary Cluster for Applied Genoproteomics Transcriptomic Platform (B.H.); and Department of Public Health (A.-F.D.), Biostatistics Unit, University of Liège, Sart-Tilman, B-4000 Liège, Belgium; and Department of Pediatrics (A.G., J.-P.B., A.-S.P.), Centre Hospitalier Universitaire de Liège, B-4032 Chênée, Belgium
| | - Benoit Hennuy
- Neuroendocrinology Unit (D.F., A.G., J.-P.B., A.-S.P.), Interdisciplinary Cluster for Applied Genoproteomics Neurosciences; Interdisciplinary Cluster for Applied Genoproteomics Transcriptomic Platform (B.H.); and Department of Public Health (A.-F.D.), Biostatistics Unit, University of Liège, Sart-Tilman, B-4000 Liège, Belgium; and Department of Pediatrics (A.G., J.-P.B., A.-S.P.), Centre Hospitalier Universitaire de Liège, B-4032 Chênée, Belgium
| | - Anne-Françoise Donneau
- Neuroendocrinology Unit (D.F., A.G., J.-P.B., A.-S.P.), Interdisciplinary Cluster for Applied Genoproteomics Neurosciences; Interdisciplinary Cluster for Applied Genoproteomics Transcriptomic Platform (B.H.); and Department of Public Health (A.-F.D.), Biostatistics Unit, University of Liège, Sart-Tilman, B-4000 Liège, Belgium; and Department of Pediatrics (A.G., J.-P.B., A.-S.P.), Centre Hospitalier Universitaire de Liège, B-4032 Chênée, Belgium
| | - Jean-Pierre Bourguignon
- Neuroendocrinology Unit (D.F., A.G., J.-P.B., A.-S.P.), Interdisciplinary Cluster for Applied Genoproteomics Neurosciences; Interdisciplinary Cluster for Applied Genoproteomics Transcriptomic Platform (B.H.); and Department of Public Health (A.-F.D.), Biostatistics Unit, University of Liège, Sart-Tilman, B-4000 Liège, Belgium; and Department of Pediatrics (A.G., J.-P.B., A.-S.P.), Centre Hospitalier Universitaire de Liège, B-4032 Chênée, Belgium
| | - Anne-Simone Parent
- Neuroendocrinology Unit (D.F., A.G., J.-P.B., A.-S.P.), Interdisciplinary Cluster for Applied Genoproteomics Neurosciences; Interdisciplinary Cluster for Applied Genoproteomics Transcriptomic Platform (B.H.); and Department of Public Health (A.-F.D.), Biostatistics Unit, University of Liège, Sart-Tilman, B-4000 Liège, Belgium; and Department of Pediatrics (A.G., J.-P.B., A.-S.P.), Centre Hospitalier Universitaire de Liège, B-4032 Chênée, Belgium
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16
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Lim WL, Idris MM, Kevin FS, Soga T, Parhar IS. Maternal Dexamethasone Exposure Alters Synaptic Inputs to Gonadotropin-Releasing Hormone Neurons in the Early Postnatal Rat. Front Endocrinol (Lausanne) 2016; 7:117. [PMID: 27630615 PMCID: PMC5005956 DOI: 10.3389/fendo.2016.00117] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Accepted: 08/11/2016] [Indexed: 11/18/2022] Open
Abstract
Maternal dexamethasone [(DEX); a glucocorticoid receptor agonist] exposure delays pubertal onset and alters reproductive behavior in the adult offspring. However, little is known whether maternal DEX exposure affects the offspring's reproductive function by disrupting the gonadotropin-releasing hormone (GnRH) neuronal function in the brain. Therefore, this study determined the exposure of maternal DEX on the GnRH neuronal spine development and synaptic cluster inputs to GnRH neurons using transgenic rats expressing enhanced green fluorescent protein (EGFP) under the control of GnRH promoter. Pregnant females were administered with DEX (0.1 mg/kg) or vehicle (VEH, water) daily during gestation day 13-20. Confocal imaging was used to examine the spine density of EGFP-GnRH neurons by three-dimensional rendering and synaptic cluster inputs to EGFP-GnRH neurons by synapsin I immunohistochemistry on postnatal day 0 (P0) males. The spine morphology and number on GnRH neurons did not change between the P0 males following maternal DEX and VEH treatment. The number of synaptic clusters within the organum vasculosum of the lamina terminalis (OVLT) was decreased by maternal DEX exposure in P0 males. Furthermore, the number and levels of synaptic cluster inputs in close apposition with GnRH neurons was decreased following maternal DEX exposure in the OVLT region of P0 males. In addition, the postsynaptic marker molecule, postsynaptic density 95, was observed in GnRH neurons following both DEX and VEH treatment. These results suggest that maternal DEX exposure alters neural afferent inputs to GnRH neurons during early postnatal stage, which could lead to reproductive dysfunction during adulthood.
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Affiliation(s)
- Wei Ling Lim
- Brain Research Institute, School of Medicine and Health Sciences, Monash University Malaysia, Petaling Jaya, Malaysia
| | - Marshita Mohd Idris
- Brain Research Institute, School of Medicine and Health Sciences, Monash University Malaysia, Petaling Jaya, Malaysia
| | - Felix Suresh Kevin
- Brain Research Institute, School of Medicine and Health Sciences, Monash University Malaysia, Petaling Jaya, Malaysia
| | - Tomoko Soga
- Brain Research Institute, School of Medicine and Health Sciences, Monash University Malaysia, Petaling Jaya, Malaysia
- *Correspondence: Tomoko Soga,
| | - Ishwar S. Parhar
- Brain Research Institute, School of Medicine and Health Sciences, Monash University Malaysia, Petaling Jaya, Malaysia
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17
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Bhattarai JP, Park SJ, Chun SW, Cho DH, Han SK. Activation of synaptic and extrasynaptic glycine receptors by taurine in preoptic hypothalamic neurons. Neurosci Lett 2015; 608:51-6. [PMID: 26453764 DOI: 10.1016/j.neulet.2015.10.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2015] [Revised: 09/28/2015] [Accepted: 10/03/2015] [Indexed: 10/22/2022]
Abstract
Taurine is an essential amino-sulfonic acid having a fundamental function in the brain, participating in both cell volume regulation and neurotransmission. Using a whole cell voltage patch clamp technique, the taurine-activated neurotransmitter receptors in the preoptic hypothalamic area (PHA) neurons were investigated. In the first set of experiments, different concentrations of taurine were applied on PHA neurons. Taurine-induced responses were concentration-dependent. Taurine-induced currents were action potential-independent and sensitive to strychnine, suggesting the involvement of glycine receptors. In addition, taurine activated not only α-homomeric, but also αβ-heteromeric glycine receptors in PHA neurons. Interestingly, a low concentration of taurine (0.5mM) activated glycine receptors, whereas a higher concentration (3mM) activated both glycine and gamma-aminobutyric acid A (GABAA) receptors in PHA neurons. These results suggest that PHA neurons are influenced by taurine and respond via glycine and GABAA receptors.
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Affiliation(s)
- Janardhan Prasad Bhattarai
- Department of Oral Physiology, School of Dentistry and Institute of Oral Bioscience, Chonbuk National University, Jeonju 561-756, Republic of Korea
| | - Soo Joung Park
- Department of Oral Physiology, School of Dentistry and Institute of Oral Bioscience, Chonbuk National University, Jeonju 561-756, Republic of Korea
| | - Sang Woo Chun
- Department of Oral Physiology, College of Dentistry, Institute of Wonkwang Biomaterial and Implant, Wonkwang University, 344-2 Shinyong Dong, Iksan 570-749, Republic of Korea
| | - Dong Hyu Cho
- Department of Obstetrics and Gynecology, Chonbuk National University Hospital and School of Medicine, Jeonj 561-756, Republic of Korea.
| | - Seong Kyu Han
- Department of Oral Physiology, School of Dentistry and Institute of Oral Bioscience, Chonbuk National University, Jeonju 561-756, Republic of Korea.
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18
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Chloride Accumulators NKCC1 and AE2 in Mouse GnRH Neurons: Implications for GABAA Mediated Excitation. PLoS One 2015; 10:e0131076. [PMID: 26110920 PMCID: PMC4482508 DOI: 10.1371/journal.pone.0131076] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2015] [Accepted: 05/28/2015] [Indexed: 11/30/2022] Open
Abstract
A developmental “switch” in chloride transporters occurs in most neurons resulting in GABAA mediated hyperpolarization in the adult. However, several neuronal cell subtypes maintain primarily depolarizing responses to GABAA receptor activation. Among this group are gonadotropin-releasing hormone-1 (GnRH) neurons, which control puberty and reproduction. NKCC1 is the primary chloride accumulator in neurons, expressed at high levels early in development and contributes to depolarization after GABAA receptor activation. In contrast, KCC2 is the primary chloride extruder in neurons, expressed at high levels in the adult and contributes to hyperpolarization after GABAA receptor activation. Anion exchangers (AEs) are also potential modulators of responses to GABAA activation since they accumulate chloride and extrude bicarbonate. To evaluate the mechanism(s) underlying GABAA mediated depolarization, GnRH neurons were analyzed for 1) expression of chloride transporters and AEs in embryonic, pre-pubertal, and adult mice 2) responses to GABAA receptor activation in NKCC1-/- mice and 3) function of AEs in these responses. At all ages, GnRH neurons were immunopositive for NKCC1 and AE2 but not KCC2 or AE3. Using explants, calcium imaging and gramicidin perforated patch clamp techniques we found that GnRH neurons from NKCC1-/- mice retained relatively normal responses to the GABAA agonist muscimol. However, acute pharmacological inhibition of NKCC1 with bumetanide eliminated the depolarization/calcium response to muscimol in 40% of GnRH neurons from WT mice. In the remaining GnRH neurons, HCO3- mediated mechanisms accounted for the remaining calcium responses to muscimol. Collectively these data reveal mechanisms responsible for maintaining depolarizing GABAA mediated transmission in GnRH neurons.
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Zhu J, Xu XH, Knight GE, He C, Burnstock G, Xiang Z. A subpopulation of gonadotropin-releasing hormone neurons in the adult mouse forebrain is γ-Aminobutyric acidergic. J Neurosci Res 2015; 93:1611-21. [DOI: 10.1002/jnr.23610] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Revised: 05/30/2015] [Accepted: 06/01/2015] [Indexed: 11/07/2022]
Affiliation(s)
- Jiao Zhu
- Department of Neurobiology; Key Laboratory of Molecular Neurobiology; Ministry of Education; Second Military Medical University; Shanghai People's Republic of China
| | - Xiao-hui Xu
- School of Life Science; Shanghai University; Shanghai People's Republic of China
| | - Gillian E. Knight
- Autonomic Neuroscience Centre; University College Medical School; London United Kingdom
| | - Cheng He
- Department of Neurobiology; Key Laboratory of Molecular Neurobiology; Ministry of Education; Second Military Medical University; Shanghai People's Republic of China
| | - Geoffrey Burnstock
- Autonomic Neuroscience Centre; University College Medical School; London United Kingdom
- Department of Pharmacology and Therapeutics; The University of Melbourne; Melbourne Australia
| | - Zhenghua Xiang
- Department of Neurobiology; Key Laboratory of Molecular Neurobiology; Ministry of Education; Second Military Medical University; Shanghai People's Republic of China
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20
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Sukhbaatar U, Mijiddorj T, Oride A, Kanasaki H. Stimulation of δ subunit-containing GABAA receptor by DS1 increases GnRH receptor expression but reduces GnRH mRNA expression in GnRH-producing GT1-7 cells. Endocrine 2015; 49:222-30. [PMID: 25355308 DOI: 10.1007/s12020-014-0464-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/10/2014] [Accepted: 10/23/2014] [Indexed: 12/23/2022]
Abstract
Acting via ionotropic GABAA receptors, the neurotransmitter γ-aminobutyric acid (GABA) is an important modulator of gonadotropin-releasing hormone (GnRH) neurons. In the present study, we examined the effect of DS1, a GABAA α4β3δ receptor agonist, on a strain of mouse hypothalamic immortalized GnRH neuronal cells, the GT1-7 cell line. DS1 increased the activities of serum-response element (SRE) and cAMP-response element (CRE) promoters, which reflect the activities of extracellular signal-regulated kinase and cAMP/protein kinase A (PKA) pathways, respectively. In G protein-coupled receptor 54 (GPR54)-overexpressing GT1-7 cells, both DS1 and kisspeptin-10 stimulated SRE promoter activity, and combined treatment with DS1 and kisspeptin further increased SRE promoter activity compared with DS1 or kisspeptin alone. Pituitary adenylate cyclase-activating polypeptide (PACAP) increased CRE promoter activity in PACAP type I receptor-overexpressing GT1-7 cells, with an effect similar to that of DS1 alone, and combined stimulation with PACAP and DS1 potentiated their individual effects. DS1 stimulated the transcriptional activity of GnRH receptor, and DS1 induced GnRH receptor mRNA and protein expression. PACAP-increased GnRH receptor expression was enhanced in the presence of DS1. However, DS1 significantly inhibited the basal expression of GnRH mRNA in GT1-7 cells. Our current observations suggest that DS1 exerts its stimulatory effect on the intracellular signal transduction system via GABAA α4β3δ receptors in GnRH-producing neurons. Stimulation with DS1 increased the expression of GnRH receptor but decreased the basal expression of GnRH mRNA.
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Affiliation(s)
- Unurjargal Sukhbaatar
- Department of Obstetrics and Gynecology, Shimane University School of Medicine, 89-1 Enya, Izumo City, Shimane Prefecture, 693-8501, Japan
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21
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Bhattarai JP, Han SK. Phasic and tonic type A γ-Aminobutryic acid receptor mediated effect of Withania somnifera on mice hippocampal CA1 pyramidal Neurons. J Ayurveda Integr Med 2015; 5:216-22. [PMID: 25624695 PMCID: PMC4296433 DOI: 10.4103/0975-9476.146541] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2013] [Revised: 03/05/2014] [Accepted: 03/13/2014] [Indexed: 11/12/2022] Open
Abstract
Background: In Nepali and Indian system of traditional medicine, Withania somnifera (WS) is considered as a rejuvenative medicine to maintain physical and mental health and has also been shown to improve memory consolidation. Objective: In this study, a methanolic extract of WS (mWS) was applied on mice hippocampal CA1 neurons to identify the receptors activated by the WS. Materials and Methods: The whole cell patch clamp recordings were performed on CA1 pyramidal neurons from immature mice (7-20 postnatal days). The cells were voltage clamped at -60 mV. Extract of WS root were applied to identify the effect of mWS. Results: The application of mWS (400 ng/μl) induced remarkable inward currents (-158.1 ± 28.08 pA, n = 26) on the CA1 pyramidal neurons. These inward currents were not only reproducible but also concentration dependent. mWS-induced inward currents remained persistent in the presence of amino acid receptor blocking cocktail (AARBC) containing blockers for the ionotropic glutamate receptors, glycine receptors and voltage-gated Na+ channel (Control: -200.3 ± 55.42 pA, AARBC: -151.5 ± 40.58 pA, P > 0.05) suggesting that most of the responses by mWS are postsynaptic events. Interestingly, these inward currents were almost completely blocked by broad GABAA receptor antagonist, bicuculline- 20 μM (BIC) (BIC: -1.46 ± 1.4 pA, P < 0.001), but only partially by synaptic GABAA receptor blocker gabazine (1 μM) (GBZ: -18.26 ± 4.70 pA, P < 0.01). Conclusion: These results suggest that WS acts on synaptic/extrasynaptic GABAA receptors and may play an important role in the process of memory and neuroprotection via activation of synaptic and extrasynaptic GABAA receptors.
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Affiliation(s)
- Janardhan Prasad Bhattarai
- Department of Oral Physiology, School of Dentistry and Institute of Oral Bioscience, Chonbuk National University, Jeonju, 561-756, Republic of Korea
| | - Seong Kyu Han
- Department of Oral Physiology, School of Dentistry and Institute of Oral Bioscience, Chonbuk National University, Jeonju, 561-756, Republic of Korea
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Watanabe M, Fukuda A, Nabekura J. The role of GABA in the regulation of GnRH neurons. Front Neurosci 2014; 8:387. [PMID: 25506316 PMCID: PMC4246667 DOI: 10.3389/fnins.2014.00387] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2014] [Accepted: 11/12/2014] [Indexed: 11/13/2022] Open
Abstract
Gonadotropin-releasing hormone (GnRH) neurons form the final common pathway for the central regulation of reproduction. Gamma-amino butyric acid (GABA) has long been implicated as one of the major players in the regulation of GnRH neurons. Although GABA is typically an inhibitory neurotransmitter in the mature adult central nervous system, most mature GnRH neurons show the unusual characteristic of being excited by GABA. While many reports have provided much insight into the contribution of GABA to the activity of GnRH neurons, the precise physiological role of the excitatory action of GABA on GnRH neurons remains elusive. This brief review presents the current knowledge of the role of GABA signaling in GnRH neuronal activity. We also discuss the modulation of GABA signaling by neurotransmitters and neuromodulators and the functional consequence of GABAergic inputs to GnRH neurons in both the physiology and pathology of reproduction.
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Affiliation(s)
- Miho Watanabe
- Department of Neurophysiology, Hamamatsu University School of Medicine Hamamatsu, Japan
| | - Atsuo Fukuda
- Department of Neurophysiology, Hamamatsu University School of Medicine Hamamatsu, Japan
| | - Junichi Nabekura
- Department of Developmental Physiology, National Institute for Physiological Sciences Okazaki, Japan ; Core Research for Evolutionary Science and Technology, Japan Science and Technology Corporation Saitama, Japan ; Department of Physiological Sciences, The Graduate School for Advanced Study Hayama, Japan
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Lee V, Maguire J. The impact of tonic GABAA receptor-mediated inhibition on neuronal excitability varies across brain region and cell type. Front Neural Circuits 2014; 8:3. [PMID: 24550784 PMCID: PMC3909947 DOI: 10.3389/fncir.2014.00003] [Citation(s) in RCA: 142] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Accepted: 01/08/2014] [Indexed: 01/19/2023] Open
Abstract
The diversity of GABAA receptor (GABAAR) subunits and the numerous configurations during subunit assembly give rise to a variety of receptors with different functional properties. This heterogeneity results in variations in GABAergic conductances across numerous brain regions and cell types. Phasic inhibition is mediated by synaptically-localized receptors with a low affinity for GABA and results in a transient, rapidly desensitizing GABAergic conductance; whereas, tonic inhibition is mediated by extrasynaptic receptors with a high affinity for GABA and results in a persistent GABAergic conductance. The specific functions of tonic versus phasic GABAergic inhibition in different cell types and the impact on specific neural circuits are only beginning to be unraveled. Here we review the diversity in the magnitude of tonic GABAergic inhibition in various brain regions and cell types, and highlight the impact on neuronal excitability in different neuronal circuits. Further, we discuss the relevance of tonic inhibition in various physiological and pathological contexts as well as the potential of targeting these receptor subtypes for treatment of diseases, such as epilepsy.
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Affiliation(s)
- Vallent Lee
- Medical Scientist Training Program and Graduate Program in Neuroscience, Sackler School of Graduate Biomedical Sciences, Tufts University Boston, MA, USA
| | - Jamie Maguire
- Department of Neuroscience, Tufts University School of Medicine Boston, MA, USA
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Bhattarai JP, Roa J, Herbison AE, Han SK. Serotonin acts through 5-HT1 and 5-HT2 receptors to exert biphasic actions on GnRH neuron excitability in the mouse. Endocrinology 2014; 155:513-24. [PMID: 24265447 DOI: 10.1210/en.2013-1692] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The effect of serotonin (5-HT) on the electrical excitability of GnRH neurons was examined using gramicidin perforated-patch electrophysiology in transgenic GnRH-green fluorescent protein mice. In diestrous female, the predominant effect of 5-HT was inhibition (70%) with 50% of these cells also exhibiting a late-onset excitation. Responses were dose dependent (EC(50) = 1.2μM) and persisted in the presence of amino acid receptor antagonists and tetrodotoxin, indicating a predominant postsynaptic action of 5-HT. Studies in neonatal, juvenile, peripubertal, and adult mice revealed that 5-HT exerted less potent responses from GnRH neurons with advancing postnatal age in both sexes. In adult male mice, 5-HT exerted less potent hyperpolarizing responses with more excitations compared with females. In addition, adult proestrous female GnRH neurons exhibited reduced inhibition and a complete absence of biphasic hyperpolarization-excitation responses. Studies using 5-HT receptor antagonists demonstrated that the activation of 5-HT(1A) receptors mediated the inhibitory responses, whereas the excitation was mediated by the activation of 5-HT(2A) receptors. The 5-HT-mediated hyperpolarization involved both potassium channels and adenylate cyclase activation, whereas the 5-HT excitation was dependent on protein kinase C. The effects of exogenous 5-HT were replicated using fluoxetine, which enhances endogenous 5-HT levels. These studies demonstrate that 5-HT exerts a biphasic action on most GnRH neurons whereby a fast 5HT(1A)-mediated inhibition occurs alongside a slow 5-HT(2A) excitation. The balance of 5-HT-evoked inhibition vs excitation is developmentally regulated, sexually differentiated, and variable across the estrous cycle and may play a role in regulation of hypothalamic-pituitary-gonadal axis throughout postnatal development.
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Affiliation(s)
- Janardhan P Bhattarai
- Department of Oral Physiology (J.P.B., S.K.H.), School of Dentistry and Institute of Oral Bioscience, Chonbuk National University, Jeonju 561-756, Republic of Korea; and Centre for Neuroendocrinology and Department of Physiology (J.R., A.E.H.), University of Otago School of Medical Sciences, Dunedin 9054, New Zealand
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25
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Activation of glycine and extrasynaptic GABA(A) receptors by taurine on the substantia gelatinosa neurons of the trigeminal subnucleus caudalis. Neural Plast 2013; 2013:740581. [PMID: 24379976 PMCID: PMC3863572 DOI: 10.1155/2013/740581] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Revised: 11/05/2013] [Accepted: 11/12/2013] [Indexed: 11/23/2022] Open
Abstract
The substantia gelatinosa (SG) of the trigeminal subnucleus caudalis (Vc) has been known for the processing and transmission of orofacial nociceptive information. Taurine, one of the most plentiful free amino-acids in humans, has proved to be involved in pain modulation. In this study, using whole-cell patch clamp technique, we investigated the direct membrane effects of taurine and the action mechanism behind taurine-mediated responses on the SG neurons of the Vc. Taurine showed non-desensitizing and repeatable membrane depolarizations and inward currents which remained in the presence of amino-acid receptors blocking cocktail (AARBC) with tetrodotoxin, indicating that taurine acts directly on the postsynaptic SG neurons. Further, application of taurine at different doses (10 μM to 3 mM) showed a concentration dependent depolarizations and inward currents with the EC50 of 84.3 μM and 723 μM, respectively. Taurine-mediated responses were partially blocked by picrotoxin (50 μM) and almost completely blocked by strychnine (2 μM), suggesting that taurine-mediated responses are via glycine receptor (GlyR) activation. In addition, taurine (1 mM) activated extrasynaptic GABAA receptor (GABAAR)-mediated currents. Taken together, our results indicate that taurine can be a target molecule for orofacial pain modulation through the activation of GlyRs and/or extrasynaptic GABAARs on the SG neurons.
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26
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Li ZX, Yu HM, Jiang KW. Tonic GABA inhibition in hippocampal dentate granule cells: its regulation and function in temporal lobe epilepsies. Acta Physiol (Oxf) 2013; 209:199-211. [PMID: 23865761 DOI: 10.1111/apha.12148] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2013] [Revised: 05/06/2013] [Accepted: 07/12/2013] [Indexed: 01/06/2023]
Abstract
Both human and experimental evidence strongly supports the view of brain region- and cell-specific changes in tonic GABA inhibition in temporal lobe epilepsies (TLE). This 'tonic' form of signalling is not time-locked to presynaptic action potentials, which depends upon detection of ambient GABA by extrasynaptic GABAA receptors (GABAA Rs). Extrasynaptic GABAA Rs have distinct physiological and pharmacological features, including high GABA-binding affinity and low desensitization and a variety of the specific subunit combinations (α4δ-,α6δ-,α5γ-,ε-containing receptors). These features closely contribute to the function of tonic GABA current, which is preserved properly or increased in dentate gyrus in models of TLE, even in the face of a loss of synaptic inhibition and inhibitory interneurones. Markedly reduced tonic GABA inhibition may facilitate an episode of epilepsy, while persistent elevated tonic inhibition may contribute to the onset of spontaneous recurrent seizures. In dentate granule cells, tonic GABA inhibition is positively modulated by endogenous neurosteroids and other factors, which undergo changes related to hormonal status after TLE. Tonic inhibition regulates neuronal excitability through its effects on membrane potential by both offsetting the threshold and reducing the frequency of action potentials and input resistance. Therefore, extrasynaptic GABAA Rs are expected to be the most important pharmacological targets in TLE. It is likely that both elevate the ambient GABA concentration and potentiate the tonic currents, contributing to the antiepileptic effects.
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Affiliation(s)
- Z.-X. Li
- Department of Neurology; The Children's Hospital Zhejiang University School of Medicine; Hangzhou; China
| | - H.-M. Yu
- Department of Neonatology; The Children's Hospital Zhejiang University School of Medicine; Hangzhou; China
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27
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In vivo recordings of GnRH neuron firing reveal heterogeneity and dependence upon GABAA receptor signaling. J Neurosci 2013; 33:9394-401. [PMID: 23719807 DOI: 10.1523/jneurosci.0533-13.2013] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The gonadotropin-releasing hormone (GnRH) neurons are the key cells regulating fertility in all mammalian species. The scattered distribution of these neurons has made investigation of their properties extremely difficult and the key goal of recording their electrical activity in vivo near impossible. The caudal-most extension of the GnRH neuron continuum brings some cells very close to the base of the brain at the level of the anterior hypothalamic area. Taking insight from this, we developed an experimental procedure in anesthetized GnRH-GFP mice that allows the electrical activity of these GnRH neurons to be recorded in vivo. On-cell recordings revealed that the majority of GnRH neurons (86%) were spontaneously active, exhibiting a range of firing patterns, although only a minority (15%) exhibited burst firing. Mean firing frequencies ranged from 0.06 to 3.65 Hz, with the most common interspike interval being ~500 ms. All GnRH neurons tested were activated by AMPA and kisspeptin. Whereas the GABAA receptor agonist muscimol evoked excitatory, inhibitory, or mixed effects on GnRH neuron firing, the GABAA receptor antagonist picrotoxin resulted in a consistent suppression of firing. These observations represent the first electrical recordings of GnRH neurons in vivo. They reveal that GnRH neurons in vivo exhibit considerable heterogeneity in their firing patterns with both similarities and differences to firing in vitro. These variable patterns of firing in vivo are found to be critically dependent upon ongoing GABAA receptor signaling.
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Bhattarai JP, Park SJ, Han SK. Potentiation of NMDA Receptors by Withania somnifera on Hippocampal CA1 Pyramidal Neurons. THE AMERICAN JOURNAL OF CHINESE MEDICINE 2013; 41:503-13. [DOI: 10.1142/s0192415x13500365] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
In Ayurveda,Withania somnifera (WS) is used as a medicine to maintain mental and physical health as well as to enhance memory. In this study, the methanolic extract of WS(mWS) was tested for its electrical influence on hippocampal CA1 pyramidal neurons using a patch clamp technique. In current clamp mode under a high chloride pipette solution, mWS (400 ng/μl) induced remarkable membrane depolarization (9.75 ± 2.54 mV, n = 6) of CA1 neurons. The mWS-induced depolarization was dose-dependent, reproducible, and persistent in the presence of 0.5 μM tetrodotoxin (TTX, 10.17 ± 0.04 mV, n = 6). In voltage clamp mode (holding potential = -60 mV), mWS induced a dose-dependent non-desensitizing inward current that persisted in the presence of TTX (0.5 μM), suggesting that the response induced by mWS was purely a postsynaptic event. Interestingly, these inward currents were partially blocked by strychnine, a glycine receptor blocker. Further, mWS potentiated the NMDA response in hippocampal CA1 neurons at low concentrations. Overall, these results suggest that there are compounds in WS with possible glycine mimetic activities, which may be potential targets for inducing memory consolidation in hippocampal CA1 neurons.
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Affiliation(s)
- Janardhan Prasad Bhattarai
- Department of Oral Physiology, School of Dentistry and Institute of Oral Bioscience, Chonbuk National University, Jeonju 561-756, Republic of Korea
| | - Soo Joung Park
- Department of Oral Physiology, School of Dentistry and Institute of Oral Bioscience, Chonbuk National University, Jeonju 561-756, Republic of Korea
| | - Seong Kyu Han
- Department of Oral Physiology, School of Dentistry and Institute of Oral Bioscience, Chonbuk National University, Jeonju 561-756, Republic of Korea
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29
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Kersanté F, Rowley SCS, Pavlov I, Gutièrrez-Mecinas M, Semyanov A, Reul JMHM, Walker MC, Linthorst ACE. A functional role for both -aminobutyric acid (GABA) transporter-1 and GABA transporter-3 in the modulation of extracellular GABA and GABAergic tonic conductances in the rat hippocampus. J Physiol 2013; 591:2429-41. [PMID: 23381899 PMCID: PMC3678035 DOI: 10.1113/jphysiol.2012.246298] [Citation(s) in RCA: 102] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Tonic γ-aminobutyric acid (GABA)A receptor-mediated signalling controls neuronal network excitability in the hippocampus. Although the extracellular concentration of GABA (e[GABA]) is critical in determining tonic conductances, knowledge on how e[GABA] is regulated by different GABA transporters (GATs) in vivo is limited. Therefore, we studied the role of GATs in the regulation of hippocampal e[GABA] using in vivo microdialysis in freely moving rats. Here we show that GAT-1, which is predominantly presynaptically located, is the major GABA transporter under baseline, quiescent conditions. Furthermore, a significant contribution of GAT-3 in regulating e[GABA] was revealed by administration of the GAT-3 inhibitor SNAP-5114 during simultaneous blockade of GAT-1 by NNC-711. Thus, the GABA transporting activity of GAT-3 (the expression of which is confined to astrocytes) is apparent under conditions in which GAT-1 is blocked. However, sustained neuronal activation by K+-induced depolarization caused a profound spillover of GABA into the extrasynaptic space and this increase in e[GABA] was significantly potentiated by sole blockade of GAT-3 (i.e. even when uptake of GAT-1 is intact). Furthermore, experiments using tetrodotoxin to block action potentials revealed that GAT-3 regulates extrasynaptic GABA levels from action potential-independent sources when GAT-1 is blocked. Importantly, changes in e[GABA] resulting from both GAT-1 and GAT-3 inhibition directly precipitate changes in tonic conductances in dentate granule cells as measured by whole-cell patch-clamp recording. Thus, astrocytic GAT-3 contributes to the regulation of e[GABA] in the hippocampus in vivo and may play an important role in controlling the excitability of hippocampal cells when network activity is increased.
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Affiliation(s)
- Flavie Kersanté
- Neurobiology of Stress and Behaviour Research Group, Henry Wellcome Laboratories for Integrative Neuroscience and Endocrinology, School of Clinical Sciences, University of Bristol, Dorothy Hodgkin Building, Whitson Street, Bristol BS1 3NY, UK
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Lee K, Liu X, Herbison AE. Burst firing in gonadotrophin-releasing hormone neurones does not require ionotrophic GABA or glutamate receptor activation. J Neuroendocrinol 2012; 24:1476-83. [PMID: 22831560 DOI: 10.1111/j.1365-2826.2012.02360.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/20/2012] [Revised: 07/11/2012] [Accepted: 07/19/2012] [Indexed: 11/28/2022]
Abstract
Burst firing is a feature of many neuroendocrine cell types, including the hypothalamic gonadotrophin-releasing hormone (GnRH) neurones that control fertility. The role of intrinsic and extrinsic influences in generating GnRH neurone burst firing is presently unclear. In the present study, we investigated the role of fast amino acid transmission in burst firing by examining the effects of receptor antagonists on bursting displayed by green fluorescent protein GnRH neurones in sagittal brain slices prepared from adult male mice. Blockade of AMPA and NMDA glutamate receptors with a cocktail of CNQX and AP5 was found to have no effects on burst firing in GnRH neurones. The frequency of bursts, dynamics of individual bursts, or percentage of firing clustered in bursts was not altered. Similarly, GABA(A) receptor antagonists bicuculline and picrotoxin had no effects upon burst firing in GnRH neurones. To examine the importance of both glutamate and GABA ionotrophic signalling, a cocktail including picrotoxin, CNQX and AP5 was used but, again, this was found to have no effects on GnRH neurone burst firing. To further question the impact of endogenous amino acid release on burst firing, electrical activation of anteroventral periventricular nuclei GABA/glutamate inputs to GnRH neurones was undertaken and found to have no impact on burst firing. Taken together, these observations indicate that bursting in GnRH neurones is not dependent upon acute ionotrophic GABA and glutamate signalling and suggest that extrinsic inputs to GnRH neurones acting through AMPA, NMDA and GABA(A) receptors are unlikely to be required for burst initiation in these cells.
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Affiliation(s)
- K Lee
- Centre for Neuroendocrinology and Department of Physiology, University of Otago, Dunedin, New Zealand
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31
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Cho DH, Bhattarai JP, Han SK. GABAA Receptor- and Non-NMDA Glutamate Receptor-Mediated Actions of Korean Red Ginseng Extract on the Gonadotropin Releasing Hormone Neurons. J Ginseng Res 2012; 36:47-54. [PMID: 23717103 PMCID: PMC3659566 DOI: 10.5142/jgr.2012.36.1.47] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2011] [Revised: 11/30/2011] [Accepted: 11/30/2011] [Indexed: 11/18/2022] Open
Abstract
Korean red ginseng (KRG) has been used worldwide as a traditional medicine for the treatment of various reproductive diseases. Gonadotropin releasing hormone (GnRH) neurons are the fundamental regulators of pulsatile release of gonadotropin required for fertility. In this study, an extract of KRG (KRGE) was applied to GnRH neurons to identify the receptors activated by KRGE. The brain slice patch clamp technique in whole cell and perforated patch was used to clarify the effect of KRGE on the membrane currents and membrane potentials of GnRH neurons. Application of KRGE (3 μg/μL) under whole cell patch induced remarkable inward currents (56.17±7.45 pA, n=25) and depolarization (12.91±3.80 mV, n=4) in GnRH neurons under high Cl- pipette solution condition. These inward currents were not only reproducible, but also concentration dependent. In addition, inward currents and depolarization induced by KRGE persisted in the presence of the voltage gated Na+ channel blocker tetrodotoxin (TTX), suggesting that the responses by KRGE were postsynaptic events. Application of KRGE under the gramicidin perforated patch induced depolarization in the presence of TTX suggesting its physiological significance on GnRH response. Further, the KRGE-induced inward currents were partially blocked by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; non-NMDA glutamate receptor antagonist, 10 μM) or picrotoxin (PIC; GABAA receptor antagonist, 50 μM), and almost blocked by PIC and CNQX mixture. Taken together, these results suggest that KRGE contains ingredients with possible GABA and non-NMDA glutamate receptor mimetic activity, and may play an important role in the endocrine function of reproductive physiology, via activation of GABAA and non-NMDA glutamate receptors in GnRH neurons.
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Affiliation(s)
- Dong Hyu Cho
- Department of Obstetrics and Gynecology, Chonbuk National University Medical School, Jeonju 561-712, Korea
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Herbison AE, Moenter SM. Depolarising and hyperpolarising actions of GABA(A) receptor activation on gonadotrophin-releasing hormone neurones: towards an emerging consensus. J Neuroendocrinol 2011; 23:557-69. [PMID: 21518033 PMCID: PMC3518440 DOI: 10.1111/j.1365-2826.2011.02145.x] [Citation(s) in RCA: 180] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The gonadotrophin-releasing hormone (GnRH) neurones represent the final output neurones of a complex neuronal network that controls fertility. It is now appreciated that GABAergic neurones within this network provide an important regulatory influence on GnRH neurones. However, the consequences of direct GABA(A) receptor activation on adult GnRH neurones have been controversial for nearly a decade now, with both hyperpolarising and depolarising effects being reported. This review provides: (i) an overview of GABA(A) receptor function and its investigation using electrophysiological approaches and (ii) re-examines the past and present results relating to GABAergic regulation of the GnRH neurone, with a focus on mouse brain slice data. Although it remains difficult to reconcile the results of the early studies, there is a growing consensus that GABA can act through the GABA(A) receptor to exert both depolarising and hyperpolarising effects on GnRH neurones. The most recent studies examining the effects of endogenous GABA release on GnRH neurones indicate that the predominant action is that of excitation. However, we are still far from a complete understanding of the effects of GABA(A) receptor activation upon GnRH neurones. We argue that this will require not only a better understanding of chloride ion homeostasis in individual GnRH neurones, and within subcellular compartments of the GnRH neurone, but also a more integrative view of how multiple neurotransmitters, neuromodulators and intrinsic conductances act together to regulate the activity of these important cells.
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Affiliation(s)
- A E Herbison
- Centre for Neuroendocrinology and Department of Physiology, University of Otago School of Medical Sciences, Dunedin, New Zealand.
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