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Aghayeva A, Gok Yurtseven D, Hasanoglu Akbulut N, Eyigor O. Immunohistochemical determination of the excitatory and inhibitory axonal endings contacting NUCB2/nesfatin-1 neurons. Neuropeptides 2024; 103:102401. [PMID: 38157780 DOI: 10.1016/j.npep.2023.102401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/14/2023] [Revised: 12/14/2023] [Accepted: 12/17/2023] [Indexed: 01/03/2024]
Abstract
Nesfatin-1 is an anorexigenic peptide suppressing food intake and is synthesized and secreted by neurons located in the hypothalamus. Our study was aimed to demonstrate the effect of excitatory and inhibitory neurotransmitters on NUCB2/nesfatin-1 neurons. In this context, dual peroxidase immunohistochemistry staining was performed using NUCB2/nesfatin-1 primary antibody with each of the primary antibodies of vesicular transporter proteins applied as markers for neurons using glutamate, acetylcholine, and GABA as neurotransmitters. In double labeling applied on floating sections, the NUCB2/nesfatin-1 reaction was determined in brown color with diaminobenzidine, while vesicular carrier proteins were marked in black. Slides were analyzed to determine the ratio of nesfatin-1 neurons in the three hypothalamic nucleus in contact with a relevant vesicular carrier protein. The ratios of NUCB2/nesfatin-1 neurons with the innervation were compared among neurotransmitters. In addition, possible gender differences between males and females were examined. The difference in the number of VGLUT2-contacting NUCB2/nesfatin-1 neurons was significantly higher in males when compared to females. When both genders were compared in different nuclei, it was seen that there was no statistical significance in terms of the percentage of NUCB2/nesfatin-1 neuron apposition with VGLUT3. The statistical evaluation showed that number of NUCB2/nesfatin-1 neurons receiving GABAergic innervation is higher in males when compared to females (*p ≤ 0.05; p = 0.045). When the axonal contact of vesicular neurotransmitter transporter proteins was compared between the neurotransmitters, it was determined that the most prominent innervation is GABAergic. In the supraoptic region, no contacts of VAChT-containing axons were found on NUCB2/nesfatin-1 neurons in both female and male subjects. In conclusion, it is understood that both excitatory and inhibitory neurons can innervate the NUCB2/nesfatin-1 neurons and the glutamatergic system is effective in the excitatory innervation while the GABAergic system plays a role in the inhibitory mechanism.
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Affiliation(s)
- Aynura Aghayeva
- Department of Histology and Embryology, Bursa Uludag University Faculty of Medicine, Bursa, Türkiye
| | - Duygu Gok Yurtseven
- Department of Histology and Embryology, Bursa Uludag University Faculty of Medicine, Bursa, Türkiye
| | - Nursel Hasanoglu Akbulut
- Department of Histology and Embryology, Bursa Uludag University Faculty of Medicine, Bursa, Türkiye
| | - Ozhan Eyigor
- Department of Histology and Embryology, Bursa Uludag University Faculty of Medicine, Bursa, Türkiye.
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2
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Pei Z, He Y, Bean JC, Yang Y, Liu H, Yu M, Yu K, Hyseni I, Cai X, Liu H, Qu N, Tu L, Conde KM, Wang M, Li Y, Yin N, Zhang N, Han J, Potts CHS, Scarcelli NA, Yan Z, Xu P, Wu Q, He Y, Xu Y, Wang C. Gabra5 plays a sexually dimorphic role in POMC neuron activity and glucose balance. Front Endocrinol (Lausanne) 2022; 13:889122. [PMID: 36120438 PMCID: PMC9471380 DOI: 10.3389/fendo.2022.889122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/03/2022] [Accepted: 08/15/2022] [Indexed: 11/25/2022] Open
Abstract
Pro-opiomelanocortin (POMC) neurons are important for the regulation of body weight and glucose balance. The inhibitory tone to POMC neurons is mediated primarily by the GABA receptors. However, the detailed mechanisms and functions of GABA receptors are not well understood. The α5 subunit of GABAA receptor, Gabra5, is reported to regulate feeding, and we found that Gabra5 is highly expressed in POMC neurons. To explore the function of Gabra5 in POMC neurons, we knocked down Gabra5 specifically from mature hypothalamic POMC neurons using the clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 strategy. This POMC-specific knock-down of Gabra5 did not affect body weight or food intake in either male or female mice. Interestingly, the loss of Gabra5 caused significant increases in the firing frequency and resting membrane potential, and a decrease in the amplitude of the miniature inhibitory postsynaptic current (mIPSC) in male POMC neurons. However, the loss of Gabra5 only modestly decreased the frequency of mIPSC in female POMC neurons. Consistently, POMC-specific knock-down of Gabra5 significantly improved glucose tolerance in male mice but not in female mice. These results revealed a sexually dimorphic role of Gabra5 in POMC neuron activity and glucose balance, independent of body weight control.
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Affiliation(s)
- Zhou Pei
- Department of Endocrinology and Inherited Metabolic Diseases, Children’s Hospital of Fudan University, Shanghai, China
- Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, United States
| | - Yang He
- Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, United States
| | - Jonathan C. Bean
- Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, United States
| | - Yongjie Yang
- Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, United States
| | - Hailan Liu
- Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, United States
| | - Meng Yu
- Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, United States
| | - Kaifan Yu
- Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, United States
| | - Ilirjana Hyseni
- Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, United States
| | - Xing Cai
- Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, United States
| | - Hesong Liu
- Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, United States
| | - Na Qu
- Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, United States
| | - Longlong Tu
- Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, United States
| | - Kristine M. Conde
- Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, United States
| | - Mengjie Wang
- Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, United States
| | - Yongxiang Li
- Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, United States
| | - Na Yin
- Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, United States
| | - Nan Zhang
- Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, United States
| | - Junying Han
- Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, United States
| | - Camille HS. Potts
- Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, United States
| | - Nikolas A. Scarcelli
- Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, United States
| | - Zili Yan
- Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, United States
| | - Pingwen Xu
- Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, The University of Illinois at Chicago, Chicago, IL, United States
| | - Qi Wu
- Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, United States
| | - Yanlin He
- Pennington Biomedical Research Center, Brain Glycemic and Metabolism Control Department, Louisiana State University, Baton Rouge, LA, United States
| | - Yong Xu
- Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, United States
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX, United States
| | - Chunmei Wang
- Children’s Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, United States
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Nakhate KT, Subhedar NK, Bharne AP, Singru PS, Kokare DM. Involvement of cocaine- and amphetamine-regulated transcript peptide in the hyperphagic and body weight promoting effects of allopregnanolone in rats. Brain Res 2013; 1532:44-55. [DOI: 10.1016/j.brainres.2013.07.055] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Revised: 07/28/2013] [Accepted: 07/30/2013] [Indexed: 11/16/2022]
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Sato I, Arima H, Ozaki N, Watanabe M, Goto M, Hayashi M, Banno R, Nagasaki H, Oiso Y. Insulin inhibits neuropeptide Y gene expression in the arcuate nucleus through GABAergic systems. J Neurosci 2006; 25:8657-64. [PMID: 16177033 PMCID: PMC6725519 DOI: 10.1523/jneurosci.2739-05.2005] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Neuropeptide Y (NPY) in the arcuate nucleus is an orexigenic hormone of which levels are regulated by humoral as well as neural signals. In this study, we examined the regulation of NPY gene expression in the arcuate nucleus in hypothalamic organotypic cultures. Dexamethasone (DEX) (10(-9) to 10(-7) M) significantly increased NPY mRNA expression, and the effects were not influenced by coincubation with the sodium channel blocker tetrodotoxin (TTX), indicating that the action of DEX is independent of action potentials. Conversely, insulin (10(-11) to 10(-9) M) significantly inhibited NPY expression stimulated by DEX, and the inhibitory action of insulin was abolished in the presence of TTX. Because GABA and its receptors are expressed in the arcuate nucleus in vivo, we examined whether GABAergic systems were involved in the insulin action. The GABAB agonist baclofen significantly inhibited NPY expression stimulated by DEX, and the inhibitory action of insulin was completely abolished in the presence of either the GABAA antagonist bicuculline or the GABAB antagonist CGP35348 (p-3-aminopropyl-p-diethoxymethyl phosphoric acid). Furthermore, increases in the GABA-synthesizing enzyme glutamic acid decarboxylase 65 (GAD65) mRNA expression preceded decreases in NPY mRNA expression in the arcuate nucleus in the cultures. Experiments in vivo also demonstrated that increases in GAD65 mRNA expression in the arcuate nucleus preceded decreases in the NPY mRNA expression in a fasting-refeeding paradigm and that intracerebroventricular injection of insulin increased GAD65 mRNA expression in the arcuate nucleus in fasted rats. These data suggest that insulin inhibits NPY gene expression in the arcuate nucleus through GABAergic systems.
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Affiliation(s)
- Ikuko Sato
- Department of Endocrinology and Diabetes, Field of Internal Medicine, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
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5
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Kalra SP, Kalra PS. Neuropeptide Y: a physiological orexigen modulated by the feedback action of ghrelin and leptin. Endocrine 2003; 22:49-56. [PMID: 14610298 DOI: 10.1385/endo:22:1:49] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/14/2003] [Accepted: 04/14/2003] [Indexed: 01/16/2023]
Abstract
Neuropeptide Y (NPY), a 36-amino-acid neuropeptide is the most potent physiological appetite transducer known. Episodic NPY neurosecretion in hypothalamic target sites is temporally linked with onset of the daily feeding pattern. Upregulation of NPY signaling in the arcuate nucleus-paraventricular nucleus (ARC-PVN) neural axis is responsible for the hyperphagia evoked by dieting, fasting, hormonal and genetic factors, and disruption in intrahypothalamic signaling. Clusters of NPY-producing neurons in the ARC that coexpress gamma- amino butyric acid and agouti-related peptide, and those in the brain stem (BS) that coexpress catecholamines and galanin, participate in disparate manners to regulate appetitive behavior. NPY receptors, Y1, Y2, and Y5, expressed by various components of the NPY network, mediate NPY-induced feeding. Imbalance in NPY signaling due either to high or low abundance of NPY at target sites elicits hyperphagia leading to increased fat accretion and obesity. Recent studies show that intermittent, feedback action of opposing afferent hormonal signals-leptin from adipose tissue and ghrelin from stomach-regulate the episodic secretion of orexigenic NPY in the PVN-ARC. Apparently, the hypothalamic NPY network is the primary common pathway intimately involved in genesis of appetite- stimulating impulses.
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Affiliation(s)
- Satya P Kalra
- Department of Neuroscience, McKnight Brain Institute, PO Box 100244, University of Florida, Gainesville, FL 32610-0244, USA.
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6
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Compère V, Li S, Leprince J, Tonon MC, Vaudry H, Pelletier G. Effect of intracerebroventricular administration of the octadecaneuropeptide on the expression of pro-opiomelanocortin, neuropeptide Y and corticotropin-releasing hormone mRNAs in rat hypothalamus. J Neuroendocrinol 2003; 15:197-203. [PMID: 12535162 DOI: 10.1046/j.1365-2826.2003.00970.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Intracerebroventricular (i.c.v.) administration of the octadecaneuropeptide (diazepam-binding inhibitor [33-50]; ODN) exerts a potent anorexigenic effect in the rat. We studied the effect of ODN on three neuropeptides involved in feeding behaviour: the orexigenic peptide neuropeptide Y (NPY) and two anorexigenic peptides, corticotropin-releasing hormone (CRH) and the pro-opiomelanocortin (POMC)-derived peptide alpha-melanocyte-stimulating hormone. The effect of i.c.v. administration of ODN (0.1 microg/kg and 1 microg/kg) on mRNA expression of the peptides in male rat hypothalamus was evaluated by semiquantitative in situ hybridization. In the arcuate nucleus, NPY-expressing neurones were mostly found in the inner zone in close proximity of the third ventricle. ODN at the dose of 0.1 microg/kg induced a significant decrease of 17.4% in NPY mRNA expression, while the depressing effect was more marked (31.4%) with the highest dose of ODN (1 microg/kg). POMC-expressing neurones were more laterally located in the arcuate nucleus. Administration of ODN at 0.1 microg/kg and 1 microg/kg doses induced increases of 33.5% and 27.4% in POMC mRNA expression, respectively. Labelling obtained with the CRH cRNA probe was essentially distributed throughout the medial parvocellular area of the hypothalamic paraventricular nucleus. ODN, at doses of 0.1 and 1 microg/kg, resulted in 17.8% and 32.8% decreases in CRH mRNA expression, respectively. The present data suggest that ODN might exert its anorexigenic effect by increasing mRNA expression of POMC and decreasing mRNA expression of NPY in the arcuate nucleus.
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Affiliation(s)
- V Compère
- European Institute for Peptide Research (IFRMP 23), Laboratory of Cellular and Molecular Neuroendocrinology, INSERM U413, UA CNRS, University of Rouen, Mont-Saint-Aignan, France
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7
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Bäckberg M, Collin M, Ovesjö ML, Meister B. Chemical coding of GABA(B) receptor-immunoreactive neurones in hypothalamic regions regulating body weight. J Neuroendocrinol 2003; 15:1-14. [PMID: 12535164 DOI: 10.1046/j.1365-2826.2003.00843.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Gamma-aminobutyric acid (GABA) interacts with hypothalamic neuronal pathways regulating feeding behaviour. GABA has been reported to stimulate feeding via both ionotropic GABA(A) and metabotropic GABA(B) receptors. The functional form of the GABA(B) receptor is a heterodimer consisting of GABA(B) receptor-1 (GABA(B)R1) and GABA(B) receptor-2 (GABA(B)R2) proteins. Within the heterodimer, the GABA-binding site is localized to GABA(B)R1. In the present study, we used an antiserum to the GABA(B)R1 protein in order to investigate the cellular localization of GABA(B)R1-immunoreactive neurones in discrete hypothalamic regions implicated in the control of body weight. The colocalization of GABA(B)R1 immunoreactivity with different chemical messengers that regulate food intake was analysed. GABA(B)R1-immunoreactive cell bodies were found in the periventricular, paraventricular (PVN), supraoptic, arcuate, ventromedial hypothalamic, dorsomedial hypothalamic, tuberomammillary nuclei and lateral hypothalamic area (LHA). Direct double-labelling showed that glutamic acid decarboxylase (GAD)-positive terminals were in close contact with GABA(B)R1-containing cell bodies located in all these regions. In the ventromedial part of the arcuate nucleus, GABA(B)R1-immunoreactive cell bodies were found to contain neuropeptide Y, agouti-related peptide (AGRP) and GAD. In the ventrolateral part of the arcuate nucleus, GABA(B)R1-immunoreactive cell bodies were shown to contain pro-opiomelanocortin and cocaine- and amphetamine-regulated transcript. In the LHA, GABA(B)R1 immunoreactivity was present in both melanin-concentrating hormone- and orexin-containing cell populations. In the tuberomammillary nucleus, GABA(B)R1-immunoreactive cell bodies expressed histidine decarboxylase, a marker for histamine-containing neurones. In addition, GAD and AGRP were found to be colocalized in some nerve terminals surrounding GABA(B)R1-immunoreactive cell bodies in the parvocellular part of the PVN. The results may provide a morphological basis for the understanding of how GABA regulates the hypothalamic control of food intake and body weight via GABA(B) receptors.
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Affiliation(s)
- M Bäckberg
- Department of Neuroscience, The Retzius Laboratory, Karolinska Institutet, Stockholm, Sweden
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8
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Ovesjö ML, Gamstedt M, Collin M, Meister B. GABAergic nature of hypothalamic leptin target neurones in the ventromedial arcuate nucleus. J Neuroendocrinol 2001; 13:505-16. [PMID: 11412337 DOI: 10.1046/j.1365-2826.2001.00662.x] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Leptin is an adipose tissue-derived cytokine hormone, which reduces body weight via interactions with hypothalamic neurones. Leptin receptors capable of activating the JAK-STAT signal transduction pathway are expressed at high levels in the hypothalamus, particularly in the arcuate nucleus. In order to identify the chemical mediators of leptin's action in the hypothalamus, we have examined whether GABA neurones of the hypothalamic arcuate nucleus contain leptin receptors and the leptin-activated transcription factor STAT3. GABAergic neurones, as visualized by antisera to the GABA-synthesizing enzyme glutamic acid decarboxylase (GAD) and GABA, were demonstrated in the ventromedial and ventrolateral parts of the arcuate nucleus. GABA neurones in the ventromedial arcuate nucleus were shown to contain leptin receptor immunoreactivity, as revealed using an antiserum generated to a sequence common to all isoforms of the leptin receptor (Ob-R), as well as an antiserum generated to the carboxy-terminal end of the long leptin receptor (Ob-Rb), and immunoreactivity for the leptin-induced signal transduction molecule STAT3. Ventromedial GABA neurones were also shown to contain neuropeptide Y, whereas ventrolateral proopiomelanocortin-containing neurones lacked GAD and GABA immunoreactivity. Levels of mRNA for GAD65, GAD67 and the vesicular GABA transporter (VGAT) were analysed in the arcuate nucleus of leptin-deficient ob/ob mice and lean control mice by in situ hybridization. No significant differences in GAD65, GAD67 or VGAT mRNA were detected in the arcuate nucleus of ob/ob mice as compared to lean control mice. The presence of leptin receptor and STAT3 in GABAergic arcuate neurones, but absence of changes in gene transcription for GAD and VGAT mRNA suggests, that leptin does not transcriptionally regulate the expression of proteins involved in GABAergic transmission in arcuate neurones. However, mechanisms other than transcriptional regulation for leptin to influence arcuate GABA neurones may exist.
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Affiliation(s)
- M L Ovesjö
- Department of Neuroscience, Karolinska Institutet, SE-171 77 Stockholm, Sweden
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Moragues N, Ciofi P, Lafon P, Odessa MF, Tramu G, Garret M. cDNA cloning and expression of a γ-aminobutyric acid Areceptor ε-subunit in rat brain. Eur J Neurosci 2000. [DOI: 10.1111/j.1460-9568.2000.01343.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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10
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Bouret S, Prevot V, Croix D, Howard A, Habert-Ortoli E, Jegou S, Vaudry H, Beauvillain JC, Mitchell V. Expression of GalR1 and GalR2 galanin receptor messenger ribonucleic acid in proopiomelanocortin neurons of the rat arcuate nucleus: effect of testosterone. Endocrinology 2000; 141:1780-94. [PMID: 10803589 DOI: 10.1210/endo.141.5.7469] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Previous studies have shown that galanin-containing fibers make synaptic contacts with POMC neurons in the arcuate nucleus. However, the ability of POMC neurons to express galanin receptors has never been assessed. The present study was designed to investigate whether POMC neurons express galanin receptor messenger RNA (mRNA) and whether testosterone could modulate galanin receptor gene expression. A dual-labeling in situ hybridization histochemistry, using 35S-labeled (galanin receptors GalR1 or GalR2) and digoxigenin-labeled (POMC) riboprobes, was performed on brain sections from intact, castrated, and testosterone-replaced adult male rats. For analysis, the arcuate nucleus was divided into four rostro-caudal areas. The results revealed that both GalR1 and GalR2 mRNAs were expressed in POMC neurons. Most POMC neurons expressing galanin receptor mRNAs were found in the rostral parts of the nucleus. Castration reduced the labeling density of galanin receptor mRNAs in POMC neurons, and testosterone prevented the effects of castration in all rostro-caudal subdivisions of the arcuate nucleus. Taken together, these data indicate that galanin can directly modulate the activity of POMC neurons, via an action on GalR1 or GalR2 receptors, particularly in the rostral-arcuate nucleus. In addition, testosterone can modulate the expression of GalR1 and GalR2. Because POMC neurons located in the rostral part of the nucleus are known to project preferentially to the preoptic area, POMC neurons expressing the galanin receptor genes may play an important role in the regulation of the GnRH neuroendocrine axis.
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Affiliation(s)
- S Bouret
- INSERM U422, Institut Fédératif de Recherches 22, Laboratoire de Neuroendocrinologie et Physiopathologie Neuronale, Lille, France.
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Kalra SP, Dube MG, Pu S, Xu B, Horvath TL, Kalra PS. Interacting appetite-regulating pathways in the hypothalamic regulation of body weight. Endocr Rev 1999; 20:68-100. [PMID: 10047974 DOI: 10.1210/edrv.20.1.0357] [Citation(s) in RCA: 245] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Various aspects of the complex spatio-temporal patterning of hypothalamic signaling that leads to the development of synchronized nocturnal feeding in the rat are critically examined. Undoubtedly, as depicted in Fig. 7, a distinct ARN in the hypothalamus is involved in the control of nocturnal appetite. At least four basic elements operate within this ARN. These are: 1) A discrete appetite-driving or orexigenic network of NPY, NE, GABA, GAL, EOP, and orexin transduces and releases appetite-stimulating signals. 2) Similarly, anorexigenic signal-producing pathways (e.g., CRH, GLP-1, alpha MSH, and CART) orchestrate neural events for dissipation of appetite and to terminate feeding, possibly by interrupting NPY efflux and action at a postsynaptic level within the hypothalamus. It is possible that some of these may represent the physiologically relevant "off" switches under the influence of GABA alone, or AgrP alone, or in combination with NPY released from the NPY-, GABA-, and AgrP-coproducing neurons. 3) Recent evidence shows that neural elements in the VMN-DMN complex tonically restrain the orexigenic signals during the intermeal interval; the restraint is greatly aided by leptin's action via diminution of orexigenic (NPY) and augmentation of anorexigenic (GLP-1, alpha MSH, and CART) signals. Since interruption of neurotransmission in the VMN resulted in hyperphagia and development of leptin resistance, it seems likely that the VMN is an effector site for the restraint exercised by leptin. The daily rhythms in leptin synthesis and release are temporally dissociable because the onset of daily rise in leptin gene expression in adipocytes precedes that in leptin secretion. Nevertheless, these rhythms are in phase with daily ingestive behavior because the peak in circulating leptin levels occurs during the middle of the feeding period. These observations, coupled with the fact that circulating levels of leptin are directly related to adiposity, pose a new challenge for elucidating the precise role of leptin in daily patterning of feeding in the rat. 4) A neural timing mechanism also operates upstream from the ARN in the daily management of energy homeostasis. Although the precise anatomical boundaries are not clearly defined, this device is likely to be composed of a group of neurons that integrate incoming internal and external information for the timely onset of the drive to eat. Evidently, this network operates independently in primates, but it is entrained to the circadian time keeper in the SCN of rodents. Apart from its role in the onset of drive to eat, the circadian patterns of gene expression of NPY, GAL, and POMC denote independent control of the timing device on the synthesis and availability for release of orexigenic signals. The VMN-DMN-PVN complex is apparently an integrated constituent of the timing mechanism in this context, because lesions in each of these sites result in loss of regulated feeding. The accumulated evidence points to the PVN and surrounding neural sites within this framework as the primary sites of release and action of various orexigenic and anorexigenic signals. A novel finding is the identification of the interconnected wiring of the DMN-mPVN axis that may mediate leptin restraint on NPY-induced feeding. The chemical phenotypes of leptin and NPY target neurons in this axis remain to be identified. These multiple orexigenic and anorexigenic pathways in the hypothalamic ARN appear to represent redundancy, a characteristic of regulated biological systems to provide a "fail-safe" neural mechanism to meet an organism's constant energy needs for growth and maintenance. Within this formulation, the coexisting orexigenic signals (NPY, NE, GAL, GABA, and AgrP) represent either another level of redundancy or it is possible that these signals operate within the ARN as reinforcing agents to varying degrees under different circumstances. (ABSTRACT TRUNCATED)
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Affiliation(s)
- S P Kalra
- Department of Neuroscience, University of Florida Brain Institute, University of Florida College of Medicine, Gainesville 32610, USA.
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12
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Neuronally restricted RNA splicing regulates the expression of a novel GABAA receptor subunit conferring atypical functional properties [corrected; erratum to be published]. J Neurosci 1997. [PMID: 9185540 DOI: 10.1523/jneurosci.17-13-05027.1997] [Citation(s) in RCA: 166] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
We report the isolation and characterization of a cDNA encoding a novel member of the GABA receptor gene family, epsilon. This polypeptide is 506 amino acids in length and exhibits its greatest amino acid sequence identity with the GABAA receptor gamma3 subunit (47%), although this degree of homology is not sufficient for it to be classified as a fourth gamma subunit. The epsilon subunit coassembles with GABAA receptor alpha and beta subunits in Xenopus laevis oocytes and transfected mammalian cells to form functional GABA-gated channels. alpha1beta1epsilon GABAA receptors, like alpha1beta1gamma2s receptors, are modulated by pentobarbital and the steroid 5alpha-pregnan-3alpha-ol-20-one but, unlike alpha1beta1gamma2s receptors, are insensitive to flunitrazepam. Additionally, alpha1beta1epsilon receptors exhibit rapid desensitization kinetics, as compared with alpha1beta1 or alpha1beta1gamma2s. Northern analysis demonstrates widespread expression of a large epsilon subunit transcript in a variety of non-neuronal tissues and expression of a smaller transcript in brain and spinal cord. Sequence analysis demonstrated that the large transcript contained an unspliced intron, whereas the small transcript represents the mature mRNA, suggesting regulation of expression of the epsilon subunit via neuronally restricted RNA splicing. In situ hybridization and immunocytochemistry reveal a pattern of expression in the brain restricted primarily to the hypothalamus, suggesting a role in neuroendocrine regulation, and also to subfields of the hippocampus, suggesting a role in the modulation of long term potentiation and memory.
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Garcia de Yebenes E, Li S, Pelletier G. Regulation of proopiomelanocortin gene expression by endogenous ligands of the GABAA receptor complex as evaluated by in situ hybridization in the rat pars intermedia. Brain Res 1997; 750:277-84. [PMID: 9098553 DOI: 10.1016/s0006-8993(96)01367-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The neurotransmitter gamma-aminobutyric acid (GABA) exerts a tonic inhibitory influence on proopiomelanocortin (POMC) neurons in the hypothalamus as well as on the melanotrope cells of the intermediate lobe (IL) of the pituitary gland. Moreover, the activation of the GABAA receptor complex by different ligands has been shown to exert a negative influence on the POMC gene expression at the hypothalamic level. In order to elucidate the in vivo regulation of the POMC mRNA levels in the intermediate lobe of the pituitary by endogenous ligands of the GABAA receptor complex, we have studied the effect of intravenous (i.v.) and intracerebroventricular (i.c.v) injections of octadecaneuropeptide (ODN), a peptide derived from diazepam-binding inhibitor (DBI). The possible involvement of neurosteroids in the action of ODN on melanotropic cells was evaluated following inhibition of two enzymes involved in the biosynthesis of neurosteroids known as activators of G3BAA receptor complex: trilostane, an inhibitor of 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD), and MK-906, an inhibitor of 5 alpha-reductase. The i.v. injection of ODN produced a dose-dependent inhibition of POMC gene expression in the IL. The i.c.v. injection of ODN also depressed POMC mRNA. These effects were completely reversed by the concomitant administration of the GABAA antagonist picrotoxin. Similar results were obtained in POMC neurons in the arcuate nucleus (AN) of the hypothalamus. Trilostane administration induced an increase in POMC mRNA and also prevented the inhibitory influence of ODN. The neurosteroid pregnenolone-sulfate, a negative modulator of the GABAA receptor, also stimulated POMC gene expression. On the other hand, MK-906 produced a decrease in mRNA levels and could not reverse the effect of ODN. The results indicate that activation of the GABAA receptor complex by the endogenous benzodiazepine receptor ligand ODN can induce a negative regulation of POMC gene expression in the IL of the pituitary and neurons in the AN. The present results do not provide clear evidence that neurosteroids are involved in the action of ODN on POMC gene expression in the IL.
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