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Hristov M, Landzhov B, Yakimova K. Effect of leptin on nitrergic neurons in the lateral hypothalamic area and the supraoptic nucleus of rats. Biotech Histochem 2024; 99:125-133. [PMID: 38533595 DOI: 10.1080/10520295.2024.2335167] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/28/2024] Open
Abstract
The adipocyte-derived hormone, leptin, plays a key role in the maintenance of energy homeostasis. Leptin binds to the long form of its receptor, which is predominantly expressed in various hypothalamic regions, including the lateral hypothalamic area (LH) and supraoptic nucleus (SO). Several studies have suggested that leptin directly activates neuronal nitric oxide synthase, leading to increased nitric oxide production. We used histochemistry for nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) as a marker for nitric oxide synthase activity and assessed the effect of leptin on nitrergic neurons in the LH and SO of rats. We found that intraperitoneal administration of leptin led to a significant increase in the number of NADPH-d-positive neurons in the LH and SO. In addition, the intensity (optical density) of NADPH-d staining in LH and SO neurons was significantly elevated in rats that received leptin compared with saline-treated rats. These findings suggest that nitrergic neurons in the LH and SO may be implicated in mediating the central effects of leptin.
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Affiliation(s)
- Milen Hristov
- Department of Pharmacology and Toxicology, Faculty of Medicine, Medical University of Sofia, Sofia, Bulgaria
| | - Boycho Landzhov
- Department of Anatomy, Histology and Embryology, Faculty of Medicine, Medical University of Sofia, Sofia, Bulgaria
| | - Krassimira Yakimova
- Department of Pharmacology and Toxicology, Faculty of Medicine, Medical University of Sofia, Sofia, Bulgaria
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2
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Gruber T, Lechner F, Murat C, Contreras RE, Sanchez-Quant E, Miok V, Makris K, Le Thuc O, González-García I, García-Clave E, Althammer F, Krabichler Q, DeCamp LM, Jones RG, Lutter D, Williams RH, Pfluger PT, Müller TD, Woods SC, Pospisilik JA, Martinez-Jimenez CP, Tschöp MH, Grinevich V, García-Cáceres C. High-calorie diets uncouple hypothalamic oxytocin neurons from a gut-to-brain satiation pathway via κ-opioid signaling. Cell Rep 2023; 42:113305. [PMID: 37864798 PMCID: PMC10636643 DOI: 10.1016/j.celrep.2023.113305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2022] [Revised: 08/21/2023] [Accepted: 10/04/2023] [Indexed: 10/23/2023] Open
Abstract
Oxytocin-expressing paraventricular hypothalamic neurons (PVNOT neurons) integrate afferent signals from the gut, including cholecystokinin (CCK), to adjust whole-body energy homeostasis. However, the molecular underpinnings by which PVNOT neurons orchestrate gut-to-brain feeding control remain unclear. Here, we show that mice undergoing selective ablation of PVNOT neurons fail to reduce food intake in response to CCK and develop hyperphagic obesity on a chow diet. Notably, exposing wild-type mice to a high-fat/high-sugar (HFHS) diet recapitulates this insensitivity toward CCK, which is linked to diet-induced transcriptional and electrophysiological aberrations specifically in PVNOT neurons. Restoring OT pathways in diet-induced obese (DIO) mice via chemogenetics or polypharmacology sufficiently re-establishes CCK's anorexigenic effects. Last, by single-cell profiling, we identify a specialized PVNOT neuronal subpopulation with increased κ-opioid signaling under an HFHS diet, which restrains their CCK-evoked activation. In sum, we document a (patho)mechanism by which PVNOT signaling uncouples a gut-brain satiation pathway under obesogenic conditions.
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Affiliation(s)
- Tim Gruber
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), 85764 Neuherberg, Germany; German Center for Diabetes Research (DZD), 85764 Neuherberg, Germany; Department of Metabolism and Nutritional Programming, Van Andel Institute, Grand Rapids, MI 49506, USA; Department of Epigenetics, Van Andel Institute, Grand Rapids, MI 49506, USA.
| | - Franziska Lechner
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), 85764 Neuherberg, Germany; German Center for Diabetes Research (DZD), 85764 Neuherberg, Germany
| | - Cahuê Murat
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), 85764 Neuherberg, Germany; German Center for Diabetes Research (DZD), 85764 Neuherberg, Germany
| | - Raian E Contreras
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), 85764 Neuherberg, Germany; German Center for Diabetes Research (DZD), 85764 Neuherberg, Germany
| | - Eva Sanchez-Quant
- Helmholtz Pioneer Campus (HPC), Helmholtz Zentrum München, Neuherberg, Germany
| | - Viktorian Miok
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), 85764 Neuherberg, Germany; German Center for Diabetes Research (DZD), 85764 Neuherberg, Germany
| | - Konstantinos Makris
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), 85764 Neuherberg, Germany; German Center for Diabetes Research (DZD), 85764 Neuherberg, Germany; Computational Discovery Research, Institute for Diabetes and Obesity (IDO), Helmholtz Diabetes Center (HDC), Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany
| | - Ophélia Le Thuc
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), 85764 Neuherberg, Germany; German Center for Diabetes Research (DZD), 85764 Neuherberg, Germany
| | - Ismael González-García
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), 85764 Neuherberg, Germany; German Center for Diabetes Research (DZD), 85764 Neuherberg, Germany
| | - Elena García-Clave
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), 85764 Neuherberg, Germany; German Center for Diabetes Research (DZD), 85764 Neuherberg, Germany
| | | | - Quirin Krabichler
- Department of Neuropeptide Research in Psychiatry, Central Institute of Mental Health, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
| | - Lisa M DeCamp
- Department of Metabolism and Nutritional Programming, Van Andel Institute, Grand Rapids, MI 49506, USA
| | - Russell G Jones
- Department of Metabolism and Nutritional Programming, Van Andel Institute, Grand Rapids, MI 49506, USA
| | - Dominik Lutter
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), 85764 Neuherberg, Germany; German Center for Diabetes Research (DZD), 85764 Neuherberg, Germany; Computational Discovery Research, Institute for Diabetes and Obesity (IDO), Helmholtz Diabetes Center (HDC), Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany
| | - Rhiannan H Williams
- Helmholtz Zentrum München, German Research Center for Environmental Health, Institute for Neurogenomics, Ingolstädter Landstraße 1, 85764 Neuherberg, Germany
| | - Paul T Pfluger
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), 85764 Neuherberg, Germany; German Center for Diabetes Research (DZD), 85764 Neuherberg, Germany; Research Unit NeuroBiology of Diabetes, Helmholtz Zentrum München, 85764 Neuherberg, Germany; Neurobiology of Diabetes, TUM School of Medicine, Technical University Munich, 80333 Munich, Germany
| | - Timo D Müller
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), 85764 Neuherberg, Germany; German Center for Diabetes Research (DZD), 85764 Neuherberg, Germany; Department of Pharmacology and Experimental Therapy, Institute for Experimental and Clinical Pharmacology and Toxicology, Eberhard Karls Hospitals and Clinics, Tübingen, Germany
| | - Stephen C Woods
- Department of Psychiatry and Behavioral Neuroscience, University of Cincinnati, Cincinnati, OH, USA
| | - John Andrew Pospisilik
- Department of Metabolism and Nutritional Programming, Van Andel Institute, Grand Rapids, MI 49506, USA; Department of Epigenetics, Van Andel Institute, Grand Rapids, MI 49506, USA
| | - Celia P Martinez-Jimenez
- Department of Epigenetics, Van Andel Institute, Grand Rapids, MI 49506, USA; TUM School of Medicine, Technical University of Munich, Munich, Germany
| | - Matthias H Tschöp
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), 85764 Neuherberg, Germany; German Center for Diabetes Research (DZD), 85764 Neuherberg, Germany; Division of Metabolic Diseases, Department of Medicine, Technische Universität, Munich, Germany
| | - Valery Grinevich
- Department of Neuropeptide Research in Psychiatry, Central Institute of Mental Health, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany; Center for Neuroinflammation and Cardiometabolic Diseases, Georgia State University, Atlanta, GA, USA.
| | - Cristina García-Cáceres
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), 85764 Neuherberg, Germany; German Center for Diabetes Research (DZD), 85764 Neuherberg, Germany; Medizinische Klinik und Poliklinik IV, Klinikum der Universität, Ludwig-Maximilians-Universität München, 80336 Munich, Germany.
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3
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Hume C, Leng G. Oxytocin neurons: integrators of hypothalamic and brainstem circuits in the regulation of macronutrient-specific satiety. CURRENT OPINION IN PHYSIOLOGY 2019. [DOI: 10.1016/j.cophys.2019.10.015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Jurek B, Neumann ID. The Oxytocin Receptor: From Intracellular Signaling to Behavior. Physiol Rev 2018; 98:1805-1908. [DOI: 10.1152/physrev.00031.2017] [Citation(s) in RCA: 408] [Impact Index Per Article: 68.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The many facets of the oxytocin (OXT) system of the brain and periphery elicited nearly 25,000 publications since 1930 (see FIGURE 1 , as listed in PubMed), which revealed central roles for OXT and its receptor (OXTR) in reproduction, and social and emotional behaviors in animal and human studies focusing on mental and physical health and disease. In this review, we discuss the mechanisms of OXT expression and release, expression and binding of the OXTR in brain and periphery, OXTR-coupled signaling cascades, and their involvement in behavioral outcomes to assemble a comprehensive picture of the central and peripheral OXT system. Traditionally known for its role in milk let-down and uterine contraction during labor, OXT also has implications in physiological, and also behavioral, aspects of reproduction, such as sexual and maternal behaviors and pair bonding, but also anxiety, trust, sociability, food intake, or even drug abuse. The many facets of OXT are, on a molecular basis, brought about by a single receptor. The OXTR, a 7-transmembrane G protein-coupled receptor capable of binding to either Gαior Gαqproteins, activates a set of signaling cascades, such as the MAPK, PKC, PLC, or CaMK pathways, which converge on transcription factors like CREB or MEF-2. The cellular response to OXT includes regulation of neurite outgrowth, cellular viability, and increased survival. OXTergic projections in the brain represent anxiety and stress-regulating circuits connecting the paraventricular nucleus of the hypothalamus, amygdala, bed nucleus of the stria terminalis, or the medial prefrontal cortex. Which OXT-induced patterns finally alter the behavior of an animal or a human being is still poorly understood, and studying those OXTR-coupled signaling cascades is one initial step toward a better understanding of the molecular background of those behavioral effects.
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Affiliation(s)
- Benjamin Jurek
- Department of Behavioural and Molecular Neurobiology, Institute of Zoology, University of Regensburg, Regensburg, Germany
| | - Inga D. Neumann
- Department of Behavioural and Molecular Neurobiology, Institute of Zoology, University of Regensburg, Regensburg, Germany
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Hume C, Sabatier N, Menzies J. High-Sugar, but Not High-Fat, Food Activates Supraoptic Nucleus Neurons in the Male Rat. Endocrinology 2017; 158:2200-2211. [PMID: 28430937 DOI: 10.1210/en.2016-1640] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Accepted: 04/14/2017] [Indexed: 02/05/2023]
Abstract
Oxytocin is a potent anorexigen and is believed to have a role in satiety signaling. We developed rat models to study the activity of oxytocin neurons in response to voluntary consumption or oral gavage of foods using c-Fos immunohistochemistry and in vivo electrophysiology. Using c-Fos expression as an indirect marker of neural activation, we showed that the percentage of magnocellular oxytocin neurons expressing c-Fos increased with voluntary consumption of sweetened condensed milk (SCM). To model the effect of food in the stomach, we gavaged anesthetized rats with SCM. The percentage of supraoptic nucleus and paraventricular nucleus magnocellular oxytocin-immunoreactive neurons expressing c-Fos increased with SCM gavage but not with gastric distention. To further examine the activity of the supraoptic nucleus, we made in vivo electrophysiological recordings from SON neurons, where anesthetized rats were gavaged with SCM or single cream. Pharmacologically identified oxytocin neurons responded to SCM gavage with a linear, proportional, and sustained increase in firing rate, but cream gavage resulted in a transient reduction in firing rate. Blood glucose increased after SCM gavage but not cream gavage. Plasma osmolarity and plasma sodium were unchanged throughout. We show that in response to high-sugar, but not high-fat, food in the stomach, there is an increase in the activity of oxytocin neurons. This does not appear to be a consequence of stomach distention or changes in osmotic pressure. Our data suggest that the presence of specific foods with different macronutrient profiles in the stomach differentially regulates the activity of oxytocin neurons.
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Affiliation(s)
- Catherine Hume
- Centre for Integrative Physiology, School of Biomedical Sciences, University of Edinburgh, Edinburgh EH8 9XD, United Kingdom
| | - Nancy Sabatier
- Centre for Integrative Physiology, School of Biomedical Sciences, University of Edinburgh, Edinburgh EH8 9XD, United Kingdom
| | - John Menzies
- Centre for Integrative Physiology, School of Biomedical Sciences, University of Edinburgh, Edinburgh EH8 9XD, United Kingdom
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Greenwood MP, Mecawi AS, Hoe SZ, Mustafa MR, Johnson KR, Al-Mahmoud GA, Elias LLK, Paton JFR, Antunes-Rodrigues J, Gainer H, Murphy D, Hindmarch CCT. A comparison of physiological and transcriptome responses to water deprivation and salt loading in the rat supraoptic nucleus. Am J Physiol Regul Integr Comp Physiol 2015; 308:R559-68. [PMID: 25632023 DOI: 10.1152/ajpregu.00444.2014] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Accepted: 01/21/2015] [Indexed: 01/16/2023]
Abstract
Salt loading (SL) and water deprivation (WD) are experimental challenges that are often used to study the osmotic circuitry of the brain. Central to this circuit is the supraoptic nucleus (SON) of the hypothalamus, which is responsible for the biosynthesis of the hormones, arginine vasopressin (AVP) and oxytocin (OXT), and their transport to terminals that reside in the posterior lobe of the pituitary. On osmotic challenge evoked by a change in blood volume or osmolality, the SON undergoes a function-related plasticity that creates an environment that allows for an appropriate hormone response. Here, we have described the impact of SL and WD compared with euhydrated (EU) controls in terms of drinking and eating behavior, body weight, and recorded physiological data including circulating hormone data and plasma and urine osmolality. We have also used microarrays to profile the transcriptome of the SON following SL and remined data from the SON that describes the transcriptome response to WD. From a list of 2,783 commonly regulated transcripts, we selected 20 genes for validation by qPCR. All of the 9 genes that have already been described as expressed or regulated in the SON by osmotic stimuli were confirmed in our models. Of the 11 novel genes, 5 were successfully validated while 6 were false discoveries.
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Affiliation(s)
| | - Andre S Mecawi
- Department of Physiology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia; Department of Physiological Sciences, Institute of Biology, Federal Rural University of Rio de Janeiro, Seropedica, Brazil
| | - See Ziau Hoe
- Department of Physiology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
| | - Mohd Rais Mustafa
- Department of Pharmacology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
| | - Kory R Johnson
- Clinical Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland
| | - Ghada A Al-Mahmoud
- Department of Biological and Environmental Sciences, College of Arts and Sciences, Qatar University, Al Tarfa, Doha, Qatar
| | - Lucila L K Elias
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, São Paulo, Brazil
| | - Julian F R Paton
- School of Physiology and Pharmacology, University Walk, Bristol, United Kingdom; and
| | - Jose Antunes-Rodrigues
- Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, São Paulo, Brazil
| | - Harold Gainer
- Laboratory of Neurochemistry, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland
| | - David Murphy
- School of Clinical Sciences, University of Bristol, Bristol, United Kingdom; Department of Physiology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia
| | - Charles C T Hindmarch
- School of Clinical Sciences, University of Bristol, Bristol, United Kingdom; Department of Physiology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia;
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Luo J, Wang T, Liang S, Hu X, Li W, Jin F. Experimental gastritis leads to anxiety- and depression-like behaviors in female but not male rats. BEHAVIORAL AND BRAIN FUNCTIONS : BBF 2013; 9:46. [PMID: 24345032 PMCID: PMC3878489 DOI: 10.1186/1744-9081-9-46] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/17/2013] [Accepted: 12/10/2013] [Indexed: 02/08/2023]
Abstract
Human and animals studies support the idea that there is a gender-related co-morbidity of pain-related and inflammatory gastrointestinal (GI) diseases with psychological disorders. This co-morbidity is the evidence for the existence of GI-brain axis which consists of immune (cytokines), neural (vagus nerve) and neuroendocrine (HPA axis) pathways. Psychological stress causes disturbances in GI physiology, such as altered GI barrier function, changes in motility and secretion, development of visceral hypersensitivity, and dysfunction of inflammatory responses. Whether GI inflammation would exert impact on psychological behavior is not well established. We examined the effect of experimental gastritis on anxiety- and depression-like behaviors in male and female Sprague-Dawley rats, and evaluated potential mechanisms of action. Gastritis was induced by adding 0.1% (w/v) iodoacetamide (IAA) to the sterile drinking water for 7 days. Sucrose preference test assessed the depression-like behavior, open field test and elevated plus maze evaluated the anxiety-like behavior. IAA treatment induced gastric inflammation in rats of either gender. No behavioral abnormality or dysfunction of GI-brain axis was observed in male rats with IAA-induced gastritis. Anxiety- and depression-like behaviors were apparent and the HPA axis was hyperactive in female rats with IAA-induced gastritis. Our results show that gastric inflammation leads to anxiety- and depression-like behaviors in female but not male rats via the neuroendocrine (HPA axis) pathway, suggesting that the GI inflammation can impair normal brain function and induce changes in psychological behavior in a gender-related manner through the GI-to-brain signaling.
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Affiliation(s)
- Jia Luo
- Key Laboratory of Mental Health, Institute of Psychology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Tao Wang
- Key Laboratory of Mental Health, Institute of Psychology, Chinese Academy of Sciences, Beijing, China
| | - Shan Liang
- Key Laboratory of Mental Health, Institute of Psychology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Xu Hu
- Key Laboratory of Mental Health, Institute of Psychology, Chinese Academy of Sciences, Beijing, China
| | - Wei Li
- Key Laboratory of Mental Health, Institute of Psychology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Feng Jin
- Key Laboratory of Mental Health, Institute of Psychology, Chinese Academy of Sciences, Beijing, China
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Velmurugan S, Russell JA, Leng G. Systemic leptin increases the electrical activity of supraoptic nucleus oxytocin neurones in virgin and late pregnant rats. J Neuroendocrinol 2013; 25:383-90. [PMID: 23298261 DOI: 10.1111/jne.12016] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/11/2012] [Revised: 11/12/2012] [Accepted: 12/20/2012] [Indexed: 12/14/2022]
Abstract
In the rat hypothalamus, fasting attenuates the expression of oxytocin and this can be reversed by exogenous leptin administration. In the present study, we investigated the effects of systemically administered leptin on the electrical activity of magnocellular neurones in the supraoptic nucleus of urethane-anaesthetised rats. In virgin female rats, systemic leptin significantly excited identified oxytocin neurones with no detected effects on the patterning of activity, as reflected by hazard function analyses. The lowest dose that was consistently effective was 100 μg/i.v., and this dose had no significant effect on vasopressin neurones. In virgin rats fasted overnight, the spontaneous firing rate of oxytocin neurones was significantly lower than in unfasted rats, although leptin had a similar excitatory effect as in unfasted rats. In late pregnant rats (days 19-21 of pregnancy), spontaneous firing rates of oxytocin neurones were higher than in virgins, and the initial response to leptin was similar to that in virgin rats, although the increase in activity was more persistent. In fasted pregnant rats, the mean spontaneous firing rate of oxytocin neurones was again lower than in unfasted rats, although leptin had no significant effect even at the higher dose of 1 mg/rat. Thus, fasting reduced the spontaneous firing rates of oxytocin neurones in nonpregnant rats, and this effect could be reversed by the excitatory effects of leptin. Pregnant rats showed some evidence of leptin resistance but only after an overnight fast.
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Affiliation(s)
- S Velmurugan
- Centre for Integrative Physiology, School of Biomedical Sciences, College of Medicine and Veterinary Medicine, University of Edinburgh, Edinburgh, UK
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Abstract
Oxytocin neurons have a physiological role in food intake and energy balance. Central administration of oxytocin is powerfully anorexigenic, reducing food intake and meal duration. The central mechanisms underlying this effect of oxytocin have become better understood in the past few years. Parvocellular neurons of the paraventricular nucleus project to the caudal brainstem to regulate feeding via autonomic functions including the gastrointestinal vago-vagal reflex. In contrast, magnocellular neurons of the supraoptic and paraventricular nuclei release oxytocin from their dendrites to diffuse to distant hypothalamic targets involved in satiety. The ventromedial hypothalamus, for example, expresses a high density of oxytocin receptors but does not contain detectable oxytocin nerve fibers. Magnocellular neurons represent targets for the anorexigenic neuropeptide α-melanocyte stimulating hormone. In addition to homeostatic control, oxytocin may also have a role in reward-related feeding. Evidence suggests that oxytocin can selectively suppress sugar intake and that it may have a role in limiting the intake of palatable food by inhibiting the reward pathway.
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Affiliation(s)
- Nancy Sabatier
- Centre for Integrative Physiology, School of Biomedical Sciences, The University of EdinburghEdinburgh, UK
| | - Gareth Leng
- Centre for Integrative Physiology, School of Biomedical Sciences, The University of EdinburghEdinburgh, UK
| | - John Menzies
- Centre for Integrative Physiology, School of Biomedical Sciences, The University of EdinburghEdinburgh, UK
- *Correspondence: John Menzies, Centre for Integrative Physiology, University of Edinburgh, George Square, Edinburgh, EH8 9XD, UK. e-mail:
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Fekete C, Zséli G, Singru PS, Kádár A, Wittmann G, Füzesi T, El-Bermani W, Lechan RM. Activation of anorexigenic pro-opiomelanocortin neurones during refeeding is independent of vagal and brainstem inputs. J Neuroendocrinol 2012; 24:1423-31. [PMID: 22734660 DOI: 10.1111/j.1365-2826.2012.02354.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
After fasting, satiety is observed within 2 h after reintroducing food, accompanied by activation of anorexigenic, pro-opiomelanocortin (POMC)-synthesising neurones in the arcuate nucleus (ARC), indicative of the critical role that α-melanocyte-stimulating hormone has in the regulation of meal size during refeeding. To determine whether refeeding-induced activation of POMC neurones in the arcuate is dependent upon the vagus nerve and/or ascending brainstem pathways, bilateral subdiaphragmatic vagotomy or transection of the afferent brainstem input to one side of the ARC was performed. One day after vagotomy or 2 weeks after brain surgery, animals were fasted and then refed for 2 h. Sections containing the ARC from vagotomised animals or animals with effective transection were immunostained for c-Fos and POMC to detect refeeding-induced activation of POMC neurones. Quantitative analyses of double-labelled preparations demonstrated that sham-operated and vagotomised animals markedly increased the number of c-Fos-immunoreactive (-IR) POMC neurones with refeeding. Furthermore, transection of the ascending brainstem pathway had no effect on diminishing c-Fos-immunoreactivity in POMC neurones on either side of the ARC, although it did diminish activation in a separate, subpopulation of neurones in the dorsomedial posterior ARC (dmpARC) on the transected side. We conclude that inputs mediated via the vagus nerve and/or arising from the brainstem do not have a primary role in refeeding-induced activation of POMC neurones in the ARC, and propose that these neurones may be activated solely by direct effects of circulating hormones/metabolites during refeeding. Activation of the dmpARC by refeeding indicates a previously unrecognised role for these neurones in appetite regulation in the rat.
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Affiliation(s)
- C Fekete
- Department of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary.
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11
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van der Plasse G, Merkestein M, Luijendijk MCM, van der Roest M, Westenberg HGM, Mulder AB, Adan RAH. Food cues and ghrelin recruit the same neuronal circuitry. Int J Obes (Lond) 2012; 37:1012-9. [PMID: 23069665 DOI: 10.1038/ijo.2012.174] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2012] [Revised: 09/10/2012] [Accepted: 09/17/2012] [Indexed: 01/06/2023]
Abstract
BACKGROUND Cues that are associated with the availability of food are known to trigger food anticipatory activity (FAA). This activity is expressed as increased locomotor activity and enables an animal to prepare for maximal utilization of nutritional resources. Although the exact neural network that mediates FAA is still unknown, several studies have revealed that the medial hypothalamus is involved. Interestingly, this area is responsive to the anorexigenic hormone leptin and the orexigenic hormone ghrelin that have been shown to modulate FAA. However, how FAA is regulated by neuronal activity and how leptin and ghrelin modulate this activity is still poorly understood. OBJECTIVE We aimed to examine how the total neuronal population and individual neurons in the medial hypothalamus respond to cue-signaled food availability in awake, behaving rats. In addition, ghrelin and leptin were injected to investigate whether these hormones could have a modulatory role in the regulation of FAA. DESIGN Using in vivo electrophysiology, neuronal activity was recorded in the medial hypothalamus in freely moving rats kept on a random feeding schedule, in which a light cue signaled upcoming food delivery. Ghrelin and leptin were administered systemically following the behavioral paradigm. RESULTS The food-predictive cue induced FAA as well as a significant increase in neural activity on a population level. More importantly, a sub-population of medial hypothalamic neurons displayed highly correlated identical responses to both ghrelin and FAA, suggesting that these neurons are part of the network that regulates FAA. CONCLUSION This study reveals a role for ghrelin, but not leptin, signaling within medial hypothalamus in FAA on both a population level and in single cells, identifying a subset of neurons onto which cue information and ghrelin signaling converge, possibly to drive FAA.
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Affiliation(s)
- G van der Plasse
- Rudolf Magnus Institute of Neuroscience, Department of Neuroscience and Pharmacology, University Medical Centre Utrecht, Utrecht, The Netherlands.
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Onaka T, Takayanagi Y, Yoshida M. Roles of oxytocin neurones in the control of stress, energy metabolism, and social behaviour. J Neuroendocrinol 2012; 24:587-98. [PMID: 22353547 DOI: 10.1111/j.1365-2826.2012.02300.x] [Citation(s) in RCA: 90] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Oxytocin neurones are activated by stressful stimuli, food intake and social attachment. Activation of oxytocin neurones in response to stressful stimuli or food intake is mediated, at least in part, by noradrenaline/prolactin-releasing peptide (PrRP) neurones in the nucleus tractus solitarius, whereas oxytocin neurones are activated after social stimuli via medial amygdala neurones. Activation of oxytocin neurones induces the release of oxytocin not only from their axon terminals, but also from their dendrites. Oxytocin acts locally where released or diffuses and acts on remote oxytocin receptors widely distributed within the brain, resulting in anxiolytic, anorexic and pro-social actions. The action sites of oxytocin appear to be multiple. Oxytocin shows anxiolytic actions, at least in part, via serotoninergic neurones in the median raphe nucleus, has anorexic actions via pro-opiomelanocortin neurones in the nucleus tractus solitarius and facilitates social recognition via the medial amygdala. Stress, obesity and social isolation are major risk factors for mortality in humans. Thus, the oxytocin-oxytocin receptor system is a therapeutic target for the promotion of human health.
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Affiliation(s)
- T Onaka
- Division of Brain and Neurophysiology, Department of Physiology, Jichi Medical University, Shinotsuke-shi, Tochigi-ken, Japan.
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Abstract
PURPOSE OF REVIEW Cholecystokinin (CCK) controls nutrient delivery to the small intestine by inhibiting food intake and gastric emptying. This review deals with recent work shedding new light on how and when. RECENT FINDINGS Intestinal I-cells release CCK in response to dietary lipid and protein through mechanisms involving the G-protein-coupled receptors GPR40 and calcium-sensing receptor. Vagal afferent neurons are a primary target of CCK and are now recognized as an important site of integration of peripheral signals regulating ingestion. In addition to regulating vagal afferent nerve discharge, CCK also controls the expression of receptors and peptide neurotransmitters by these neurons; these actions are potentiated by leptin and inhibited by ghrelin. The responses of vagal afferent neurons to CCK are attenuated in obesity. Studies of human central nervous system responses using functional magnetic resonance imaging indicate activation of brainstem, hypothalamus and motor cortex by ingested fatty acid that is inhibited by a CCK-1 receptor antagonist. CCK may also play a role in adaptive responses in pancreatic islets by maintaining β-cell mass and acting as an incretin in certain circumstances. SUMMARY CCK mediates inhibition of food intake in response to ingested lipid and protein; resistance to CCK occurs in obesity and may contribute to altered mechanisms regulating food intake.
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Affiliation(s)
- Graham J Dockray
- Physiological Laboratory, Institute of Translational Medicine, University of Liverpool, Liverpool, UK.
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Abstract
During pregnancy, food intake and fat mass are increased to meet the energy demands of the growing conceptus and to prepare for the subsequent demands of lactation. A state of leptin resistance develops during pregnancy in the rat, which can facilitate the increase in food intake despite pregnancy-induced increases in leptin concentrations. Cholecystokinin (CCK) is a satiety factor that is released from the gut during feeding and acts to terminate short-term food intake. Circulating leptin concentrations can modulate the anorexic response to CCK; low leptin concentrations decrease the potency of CCK to reduce food intake. Because rats are leptin resistant by day 14 of pregnancy, it was hypothesised that the feeding response to CCK would be attenuated at that time. Nonpregnant and day 14 pregnant rats received an i.p. injection of CCK-8 (3 μg/kg body weight) or vehicle directly before the start of the dark phase. Food intake was measured 30 min after lights out. Approximately 90 min after receiving either CCK-8 or vehicle, rats were transcardially perfused with 4% paraformaldehyde. Food intake was significantly decreased in CCK-treated nonpregnant rats, although similar treatment did not reduce food intake in day 14 pregnant rats. CCK treatment lead to significant increased in c-Fos expression in the nucleus of the solitary tract (NTS) in both nonpregnant and pregnant rats compared to vehicle treatment, although the number of CCK-induced c-Fos positive cells was significantly less in pregnant rat compared to nonpregnant rats. Although CCK treatment increased the number of c-Fos positive cells in the hypothalamic paraventricular nucleus and supraoptic nucleus in nonpregnant rats, no significant increase was observed in these areas during pregnancy. These results indicate that pregnant rats are no longer responsive to the actions of CCK on short-term food intake and that CCK action in the NTS is reduced during pregnancy.
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Affiliation(s)
- S R Ladyman
- Centre for Neuroendocrinology and Department of Anatomy, University of Otago, Dunedin, New Zealand.
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