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Kim EM, Quinn JG, Reid RE, O'Hare E. Evidence for a feeding related association between melanocortin in the NTS and Neuropeptide-Y in the PVN. Appetite 2023; 188:106618. [PMID: 37257508 DOI: 10.1016/j.appet.2023.106618] [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: 03/20/2023] [Revised: 05/26/2023] [Accepted: 05/27/2023] [Indexed: 06/02/2023]
Abstract
Melanocortin and neuropeptide-Y (NPY) are both involved in feeding and energy regulation, and they have opposite effects in the paraventricular nucleus of the hypothalamus (PVN). The present study examined an interaction between melanocortin in the nucleus of the solitary tract (NTS) and NPY in the PVN. Male Sprague-Dawley rats were implanted with cannulae in the injection sites of interest. In Experiment 1, subjects received either the melanocortin 3/4-receptor (MC3/4) antagonist SHU9119 (0, 10, 50 and 100 pmol/0.5 μl) or the MC3/4 agonist MTII (0, 10, 50, 100 and 200 pmol/0.5 μl) into the NTS. Food intake was measured at 1, 2, 4, 6 and 24-h post-injection. Administration of SHU9119 into the NTS significantly and dose-dependently increased food intake at 1, 2, 4, 6 and 6-24-h, and administration of MTII into the NTS significantly and dose-dependently decreased 24-h free feeding. In Experiment 2, subjects received the MC3/4 agonist MTII (0, 10, 50, 100 and 200 pmol/0.5 μl) into the NTS just prior to NPY (0 and 1μg/0.5 μl) in the PVN. PVN injection of NPY stimulated feeding, and administration of MTII (50, 100 and 200 pmol) into the NTS significantly and dose-dependently decreased NPY-induced feeding at 2, 4, 6 and 6-24-h. These data suggest that there could be a neuronal association between melanocortin in the NTS and NPY in the PVN, and that the melanocortin system in the NTS has an antagonistic effect on NPY-induced feeding in the PVN.
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Affiliation(s)
- E-M Kim
- School of Psychology, Ulster University, Cromore Road, Coleraine, Northern Ireland, UK.
| | - J G Quinn
- School of Medicine, Queen's University Belfast, Northern Ireland, UK
| | - R E Reid
- School of Psychology, Dublin Business School, Ireland
| | - E O'Hare
- School of Psychology, Queen's University Belfast, Northern Ireland, UK
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2
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Laing BT, Jayan A, Erbaugh LJ, Park AS, Wilson DJ, Aponte Y. Regulation of body weight and food intake by AGRP neurons during opioid dependence and abstinence in mice. Front Neural Circuits 2022; 16:977642. [PMID: 36110920 PMCID: PMC9468932 DOI: 10.3389/fncir.2022.977642] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Accepted: 08/08/2022] [Indexed: 11/13/2022] Open
Abstract
Dysregulation of body weight maintenance and opioid dependence are often treated as independent disorders. Here, we assessed the effects of both acute and long-term administration of morphine with and without chemogenetic activation of agouti-related peptide (AGRP)-expressing neurons in the arcuate nucleus (ARCAGRP neurons) to elucidate whether morphine and neuronal activation affect feeding behavior and body weight. First, we characterized interactions of opioids and energy deficit in wild-type mice. We observed that opioid administration attenuated both fasting-induced refeeding and ghrelin-stimulated feeding. Moreover, antagonism of opioid receptors blocked fasting-induced refeeding behavior. Next, we interfaced chemogenetics with opioid dependence. For chemogenetic experiments of ARCAGRP neurons, we conducted a priori behavioral qualification and post-mortem FOS immunostaining verification of arcuate activation following ARCAGRP chemogenetic activation. We administered clozapine during short-term and long-term morphine administration paradigms to determine the effects of dependence on food intake and body weight. We found that morphine occluded feeding behavior characteristic of chemogenetic activation of ARCAGRP neurons. Notably, activation of ARCAGRP neurons attenuated opioid-induced weight loss but did not evoke weight gain during opioid dependence. Consistent with these findings, we observed that morphine administration did not block fasting-induced activation of the ARC. Together, these results highlight the strength of opioidergic effects on body weight maintenance and demonstrate the utility of ARCAGRP neuron manipulations as a lever to influence energy balance throughout the development of opioid dependence.
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Affiliation(s)
- Brenton T. Laing
- Neuronal Circuits and Behavior Section, National Institute on Drug Abuse Intramural Research Program, National Institutes of Health, Baltimore, MD, United States
| | - Aishwarya Jayan
- Neuronal Circuits and Behavior Section, National Institute on Drug Abuse Intramural Research Program, National Institutes of Health, Baltimore, MD, United States
| | - Lydia J. Erbaugh
- Neuronal Circuits and Behavior Section, National Institute on Drug Abuse Intramural Research Program, National Institutes of Health, Baltimore, MD, United States
| | - Anika S. Park
- Neuronal Circuits and Behavior Section, National Institute on Drug Abuse Intramural Research Program, National Institutes of Health, Baltimore, MD, United States
| | - Danielle J. Wilson
- Neuronal Circuits and Behavior Section, National Institute on Drug Abuse Intramural Research Program, National Institutes of Health, Baltimore, MD, United States
| | - Yeka Aponte
- Neuronal Circuits and Behavior Section, National Institute on Drug Abuse Intramural Research Program, National Institutes of Health, Baltimore, MD, United States
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, United States
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3
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Colon-Perez L, Montesinos J, Monsivais M. The Future of Neuroimaging and Gut-Brain Axis Research for Substance Use Disorders. Brain Res 2022; 1781:147835. [DOI: 10.1016/j.brainres.2022.147835] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 01/31/2022] [Accepted: 02/10/2022] [Indexed: 12/19/2022]
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4
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Jewett DC, Klockars A, Smith TR, Brunton C, Head MA, Tham RL, Kwilasz AJ, Hahn TW, Wiebelhaus JM, Ewan EE, Carroll RM, Grace MK, Levine AS, Olszewski PK. Effects of opioid receptor ligands in rats trained to discriminate 22 from 2 hours of food deprivation suggest a lack of opioid involvement in eating for hunger. Behav Brain Res 2020; 380:112369. [DOI: 10.1016/j.bbr.2019.112369] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Revised: 10/28/2019] [Accepted: 11/15/2019] [Indexed: 10/25/2022]
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5
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Phenotyping neurons activated in the mouse brain during restoration of salt debt. J Chem Neuroanat 2019; 101:101665. [PMID: 31398430 DOI: 10.1016/j.jchemneu.2019.101665] [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: 01/07/2019] [Revised: 07/17/2019] [Accepted: 08/05/2019] [Indexed: 11/21/2022]
Abstract
Salt overconsumption contributes to hypertension, which is a major risk factor for stroke, heart and kidney disease. Characterising neuronal pathways that may control salt consumption is therefore important for developing novel approaches for reducing salt overconsumption. Here, we identify neurons within the mouse central amygdala (CeA), lateral parabrachial nucleus (LPBN), intermediate nucleus of the solitary tract (iNTS), and caudal NTS (cNTS) that are activated and display Fos immunoreactivity in mice that have consumed salt in order to restore a salt debt, relative to salt replete and salt depleted controls. Double-label immunohistochemical studies revealed that salt restoring mice had significantly greater densities of activated enkephalin neurons within the CeA and iNTS, while statistically significant changes within the LPBN and cNTS were not observed. Furthermore, within the CeA, restoration of salt debt conferred a significant increase in the density of activated calretinin neurons, while there was no change relative to control groups in the density of activated neurons that co-expressed protein kinase C delta (PKC-δ). Taken together, these studies highlight the importance of opioid systems within the CeA and iNTS in neuronal processes associated with salt restoration, and may aid the development of future pharmacological and other strategies for reducing salt overconsumption.
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Mavanji V, Perez-Leighton CE, Kotz CM, Billington CJ, Parthasarathy S, Sinton CM, Teske JA. Promotion of Wakefulness and Energy Expenditure by Orexin-A in the Ventrolateral Preoptic Area. Sleep 2015; 38:1361-70. [PMID: 25845696 DOI: 10.5665/sleep.4970] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Accepted: 03/07/2015] [Indexed: 12/25/2022] Open
Abstract
STUDY OBJECTIVES The ventrolateral preoptic area (VLPO) and the orexin/hypocretin neuronal system are key regulators of sleep onset, transitions between vigilance states, and energy homeostasis. Reciprocal projections exist between the VLPO and orexin/hypocretin neurons. Although the importance of the VLPO to sleep regulation is clear, it is unknown whether VLPO neurons are involved in energy balance. The purpose of these studies was to determine if the VLPO is a site of action for orexin-A, and which orexin receptor subtype(s) would mediate these effects of orexin-A. We hypothesized that orexin-A in the VLPO modulates behaviors (sleep and wakefulness, feeding, spontaneous physical activity [SPA]) to increase energy expenditure. DESIGN AND MEASUREMENTS Sleep, wakefulness, SPA, feeding, and energy expenditure were determined after orexin-A microinjection in the VLPO of male Sprague-Dawley rats with unilateral cannulae targeting the VLPO. We also tested whether pretreatment with a dual orexin receptor antagonist (DORA, TCS-1102) or an OX2R antagonist (JNJ-10397049) blocked the effects of orexin-A on the sleep/wake cycle or SPA, respectively. RESULTS Orexin-A injected into the VLPO significantly increased wakefulness, SPA, and energy expenditure (SPA-induced and total) and reduced NREM sleep and REM sleep with no effect on food intake. Pretreatment with DORA blocked the increase in wakefulness and the reduction in NREM sleep elicited by orexin-A, and the OX2R antagonist reduced SPA stimulated by orexin-A. CONCLUSIONS These data show the ventrolateral preoptic area is a site of action for orexin-A, which may promote negative energy balance by modulating sleep/wakefulness and stimulating spontaneous physical activity and energy expenditure.
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Affiliation(s)
| | - Claudio E Perez-Leighton
- Center for Integrative Medicine and Innovative Science, Universidad Andres Bello, Santiago, Chile.,Escuela de Nutricion, Facultad de Medicina, Universidad Andres Bello, Santiago, Chile
| | - Catherine M Kotz
- Minneapolis VA Health Care System, Minneapolis, MN.,Geriatric Research Education and Clinical Center, Minneapolis, MN.,Minnesota Obesity Center, University of Minnesota, Saint Paul, MN.,Department of Food Science and Nutrition, University of Minnesota, Saint Paul, MN
| | - Charles J Billington
- Minneapolis VA Health Care System, Minneapolis, MN.,Minnesota Obesity Center, University of Minnesota, Saint Paul, MN.,Department of Medicine, University of Minnesota, Saint Paul, MN.,Department of Food Science and Nutrition, University of Minnesota, Saint Paul, MN
| | - Sairam Parthasarathy
- Arizona Respiratory Center University of Arizona, Tucson, AZ.,Department of Medicine University of Arizona, Tucson, AZ
| | - Christopher M Sinton
- Arizona Respiratory Center University of Arizona, Tucson, AZ.,Department of Medicine University of Arizona, Tucson, AZ
| | - Jennifer A Teske
- Department of Nutritional Sciences, University of Arizona, Tucson, AZ.,Minneapolis VA Health Care System, Minneapolis, MN.,Minnesota Obesity Center, University of Minnesota, Saint Paul, MN.,Department of Food Science and Nutrition, University of Minnesota, Saint Paul, MN
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7
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De Vadder F, Gautier-Stein A, Mithieux G. Satiety and the role of μ-opioid receptors in the portal vein. Curr Opin Pharmacol 2013; 13:959-63. [PMID: 24095601 DOI: 10.1016/j.coph.2013.09.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2013] [Revised: 08/20/2013] [Accepted: 09/04/2013] [Indexed: 01/03/2023]
Abstract
Mu-opioid receptors (MORs) are known to influence food intake at the brain level, through their involvement in the food reward system. MOR agonists stimulate food intake. On the other hand, MOR antagonists suppress food intake. MORs are also active in peripheral organs, especially in the small intestine where they control the gut motility. Recently, an indirect role in the control of food intake was ascribed to MORs in the extrinsic gastrointestinal neural system. MORs present in the neurons of the portal vein walls sense blood peptides released from the digestion of dietary protein. These peptides behave as MOR antagonists. Their MOR antagonist action initiates a gut-brain circuitry resulting in the induction of intestinal gluconeogenesis, a function controlling food intake. Thus, periportal MORs are a key mechanistic link in the satiety effect of protein-enriched diets.
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Affiliation(s)
- Filipe De Vadder
- Inserm U855, Lyon, France; Université Lyon 1, Villeurbanne, France; Université de Lyon, Lyon, France
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8
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Cui RJ, Roberts BL, Zhao H, Andresen MC, Appleyard SM. Opioids inhibit visceral afferent activation of catecholamine neurons in the solitary tract nucleus. Neuroscience 2012; 222:181-90. [PMID: 22796075 DOI: 10.1016/j.neuroscience.2012.07.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2012] [Revised: 06/15/2012] [Accepted: 07/04/2012] [Indexed: 12/12/2022]
Abstract
Brainstem A2/C2 catecholamine (CA) neurons within the solitary tract nucleus (NTS) influence many homeostatic functions, including food intake, stress, respiratory and cardiovascular reflexes. They also play a role in both opioid reward and withdrawal. Injections of opioids into the NTS modulate many autonomic functions influenced by catecholamine neurons including food intake and cardiac function. We recently showed that NTS-CA neurons are directly activated by incoming visceral afferent inputs. Here we determined whether opioid agonists modulate afferent activation of NTS-CA neurons using transgenic mice with EGFP expressed under the control of the tyrosine hydroxylase promoter (TH-EGFP) to identify catecholamine neurons. The opioid agonist Met-enkephalin (Met-Enk) significantly attenuated solitary tract-evoked excitatory postsynaptic currents (ST-EPSCs) in NTS TH-EGFP neurons by 80%, an effect reversed by wash or the mu opioid receptor-specific antagonist D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH(2) (CTOP). Met-Enk had a significantly greater effect to inhibit afferent inputs onto TH-EGFP-positive neurons than EGFP-negative neurons, which were only inhibited by 50%. The mu agonist, DAMGO, also inhibited the ST-EPSC in TH-EGFP neurons in a dose-dependent manner. In contrast, neither the delta agonist DPDPE, nor the kappa agonist, U69,593, consistently inhibited the ST-EPSC amplitude. Met-Enk and DAMGO increased the paired pulse ratio, decreased the frequency, but not amplitude, of mini-EPSCs and had no effect on holding current, input resistance or current-voltage relationships in TH-EGFP neurons, suggesting a presynaptic mechanism of action on afferent terminals. Met-Enk significantly reduced both the basal firing rate of NTS TH-EGFP neurons and the ability of afferent stimulation to evoke an action potential. These results suggest that opioids inhibit NTS-CA neurons by reducing an excitatory afferent drive onto these neurons through presynaptic inhibition of glutamate release and elucidate one potential mechanism by which opioids could control autonomic functions and modulate reward and opioid withdrawal symptoms at the level of the NTS.
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Affiliation(s)
- R J Cui
- Department of Veterinary Comparative Anatomy, Physiology and Pharmacology, Washington State University, Pullman, WA 99164, USA
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9
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Mu-opioid receptors and dietary protein stimulate a gut-brain neural circuitry limiting food intake. Cell 2012; 150:377-88. [PMID: 22771138 DOI: 10.1016/j.cell.2012.05.039] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2011] [Revised: 03/02/2012] [Accepted: 05/09/2012] [Indexed: 11/21/2022]
Abstract
Intestinal gluconeogenesis is involved in the control of food intake. We show that mu-opioid receptors (MORs) present in nerves in the portal vein walls respond to peptides to regulate a gut-brain neural circuit that controls intestinal gluconeogenesis and satiety. In vitro, peptides and protein digests behave as MOR antagonists in competition experiments. In vivo, they stimulate MOR-dependent induction of intestinal gluconeogenesis via activation of brain areas receiving inputs from gastrointestinal ascending nerves. MOR-knockout mice do not carry out intestinal gluconeogenesis in response to peptides and are insensitive to the satiety effect induced by protein-enriched diets. Portal infusions of MOR modulators have no effect on food intake in mice deficient for intestinal gluconeogenesis. Thus, the regulation of portal MORs by peptides triggering signals to and from the brain to induce intestinal gluconeogenesis are links in the satiety phenomenon associated with alimentary protein assimilation.
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10
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Nixon JP, Kotz CM, Novak CM, Billington CJ, Teske JA. Neuropeptides controlling energy balance: orexins and neuromedins. Handb Exp Pharmacol 2012:77-109. [PMID: 22249811 DOI: 10.1007/978-3-642-24716-3_4] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
In this chapter, we review the feeding and energy expenditure effects of orexin (also known as hypocretin) and neuromedin. Orexins are multifunctional neuropeptides that affect energy balance by participating in regulation of appetite, arousal, and spontaneous physical activity. Central orexin signaling for all functions originates in the lateral hypothalamus-perifornical area and is likely functionally differentiated based on site of action and on interacting neural influences. The effect of orexin on feeding is likely related to arousal in some ways but is nonetheless a separate neural process that depends on interactions with other feeding-related neuropeptides. In a pattern distinct from other neuropeptides, orexin stimulates both feeding and energy expenditure. Orexin increases in energy expenditure are mainly by increasing spontaneous physical activity, and this energy expenditure effect is more potent than the effect on feeding. Global orexin manipulations, such as in transgenic models, produce energy balance changes consistent with a dominant energy expenditure effect of orexin. Neuromedins are gut-brain peptides that reduce appetite. There are gut sources of neuromedin, but likely the key appetite-related neuromedin-producing neurons are in the hypothalamus and parallel other key anorectic neuropeptide expression in the arcuate to paraventricular hypothalamic projection. As with other hypothalamic feeding-related peptides, hindbrain sites are likely also important sources and targets of neuromedin anorectic action. Neuromedin increases physical activity in addition to reducing appetite, thus producing a consistent negative energy balance effect. Together with the other various neuropeptides, neurotransmitters, neuromodulators, and neurohormones, neuromedin and orexin act in the appetite network to produce changes in food intake and energy expenditure, which ultimately influences the regulation of body weight.
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Affiliation(s)
- Joshua P Nixon
- Veterans Affairs Medical Center, Research Service (151), Minneapolis, MN, USA
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11
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Kinzeler NR, Travers SP. μ-Opioid modulation in the rostral solitary nucleus and reticular formation alters taste reactivity: evidence for a suppressive effect on consummatory behavior. Am J Physiol Regul Integr Comp Physiol 2011; 301:R690-700. [PMID: 21697523 DOI: 10.1152/ajpregu.00142.2011] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The neural control of feeding involves many neuromodulators, including the endogenous opioids that bind μ-opioid receptors (MORs). Injections of the MOR agonist, Damgo, into limbic and hypothalamic forebrain sites increase intake, particularly of palatable foods. Indeed, forebrain Damgo injections increase sucrose-elicited licking but reduce aversive responding (gaping) to quinine, suggesting that MOR activation may enhance taste palatability. A μ-opioid influence on taste reactivity has not been assessed in the brain stem. However, MORs are present in the first-order taste relay, the rostral nucleus of the solitary tract (rNST), and in the immediately subjacent reticular formation (RF), a region known to be essential for consummatory responses. Thus, to evaluate the consequences of rNST/dorsal RF Damgo in this region, we implanted rats with intraoral cannulas, electromyographic electrodes, and brain cannulas aimed at the ventral border of the rNST. Licking and gaping elicited with sucrose, water, and quinine were assessed before and after intramedullary Damgo and saline infusions. Damgo slowed the rate, increased the amplitude, and decreased the size of fluid-induced lick and gape bouts. In addition, the neutral stimulus water, which typically elicits licks, began to evoke gapes. Thus, the current results demonstrate that μ-opioid activation in the rNST/dorsal RF exerts complex effects on oromotor responding that contrast with forebrain effects and are more indicative of a suppressive, rather than a facilitatory effect on ingestion.
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Affiliation(s)
- Nicole R Kinzeler
- Department of Psychology, The Ohio State University, Columbus, Ohio, USA.
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12
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Bello NT, Patinkin ZW, Moran TH. Opioidergic consequences of dietary-induced binge eating. Physiol Behav 2011; 104:98-104. [PMID: 21539852 DOI: 10.1016/j.physbeh.2011.04.032] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2011] [Accepted: 04/22/2011] [Indexed: 12/30/2022]
Abstract
Endogenous opioids are involved in the hedonic aspects of eating. Opioid impairments and alterations have been implicated in the pathophysiology of bulimia nervosa and binge eating disorder. Specific contributions by Bartley G. Hoebel have furthered the understanding how cyclical caloric restriction and intermittent optional access to sugar solutions result in opioid-like forebrain neural alterations and dependency in rodents. The present study sought to investigate caudal brainstem and nodose ganglion mu-opioid receptor mRNA alterations in a rodent model of dietary-induced binge eating of sweetened fat (vegetable shortening blended with 10% sucrose). Five groups (n=7 or 8) of adult female Sprague Dawley rats were exposed to various dietary conditions for 6 weeks. As measured by in situ hybridization, there was reduced (approximately 25% from naive) mu-opioid receptor mRNA in the nucleus of the solitary tract (NTS) in the binge access group, which had intermittent calorie restriction and optional limited access to the sweetened fat. A similar reduction in expression was demonstrated in the continuous access group, which has unlimited optional sweetened fat and an obese phenotype. In the nodose ganglion, mu-opioid receptor mRNA was increased (approximately 30% from groups with sweetened fat access) in rats with intermittent caloric restriction alone. Our findings and the body of work from the Hoebel laboratory suggest that dietary-induced binge eating can consequentially alter opioidergic forebrain and hindbrain feeding-related neural pathways. Future work is needed to determine whether similar alterations are involved in the maintenance and progression of binge eating and other related eating pathologies.
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Affiliation(s)
- Nicholas T Bello
- Department of Animal Sciences, Rutgers, The State University of New Jersey, New Brunswick, NJ 08901, USA.
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13
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Endocrine induced changes in brain function during pregnancy. Brain Res 2010; 1364:198-215. [DOI: 10.1016/j.brainres.2010.09.062] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2010] [Revised: 09/10/2010] [Accepted: 09/16/2010] [Indexed: 02/05/2023]
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14
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Grill HJ. Leptin and the systems neuroscience of meal size control. Front Neuroendocrinol 2010; 31:61-78. [PMID: 19836413 PMCID: PMC2813996 DOI: 10.1016/j.yfrne.2009.10.005] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/14/2009] [Revised: 10/12/2009] [Accepted: 10/13/2009] [Indexed: 12/14/2022]
Abstract
The development of effective pharmacotherapy for obesity will benefit from a more complete understanding of the neural pathways and the neurochemical signals whose actions result in the reduction of the size of meals. This review examines the neural control of meal size and the integration of two principal sources of that control--satiation signals arising from the gastrointestinal tract and CNS leptin signaling. Four types of integrations that are central to the control of meal size are described and each involves the neurons of the nucleus tractus solitarius (NTS) in the dorsal hindbrain. Data discussed show that NTS neurons integrate information arising from: (1) ascending GI-derived vagal afferent projections, (2) descending neuropeptidergic projections from leptin-activated arcuate and paraventricular nucleus neurons, (3) leptin signaling in NTS neurons themselves and (4) melanocortinergic projections from NTS and hypothalamic POMC neurons to NTS neurons and melanocortinergic modulation of vagal afferent nerve terminals that are presynaptic to NTS neurons.
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Affiliation(s)
- Harvey J Grill
- Graduate Groups of Psychology and Neuroscience, University of Pennsylvania, 3720 Walnut Street, Philadelphia, PA 19104, USA
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15
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Lloret Linares C, Declèves X, Oppert JM, Basdevant A, Clement K, Bardin C, Scherrmann JM, Lepine JP, Bergmann JF, Mouly S. Pharmacology of morphine in obese patients: clinical implications. Clin Pharmacokinet 2009; 48:635-51. [PMID: 19743886 DOI: 10.2165/11317150-000000000-00000] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Morphine is an analgesic drug used to treat acute and chronic pain. Obesity is frequently associated with pain of various origins (e.g. arthritis, fibromyalgia, cancer), which increases the need for analgesic drugs. Obesity changes drug pharmacokinetics, and for certain drugs, specific modalities of prescription have been proposed for obese patients. However, scant data are available regarding the pharmacokinetics and pharmacodynamics of morphine in obesity. Prescription of morphine depends on pain relief but the occurrence of respiratory adverse effects correlates with obesity, and is not currently taken into account. Variations in the volume of distribution, elimination half-life and oral clearance of morphine, as well as recent advances in the respective roles of drug-metabolizing enzymes, catechol-O-methyltransferase and the mu opioid receptor in morphine pharmacokinetics and pharmacodynamics, may contribute to differences between obese and non-obese patients. In addition, drug-drug interactions may alter the disposition of morphine and its glucuronide metabolites, which may either increase the risk of adverse effects or reduce drug efficacy.
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Affiliation(s)
- Célia Lloret Linares
- Unit of Therapeutic Research, Department of Internal Medicine, Hôpital Lariboisière, Assistance Publique-Hôpitaux de Paris, Paris, France
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16
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Feeding association between the nucleus of the solitary tract and the ventral tegmental area. Appetite 2009; 53:457-60. [DOI: 10.1016/j.appet.2009.09.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2009] [Revised: 08/31/2009] [Accepted: 09/06/2009] [Indexed: 11/23/2022]
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17
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Beckman TR, Shi Q, Levine AS, Billington CJ. Amygdalar opioids modulate hypothalamic melanocortin-induced anorexia. Physiol Behav 2008; 96:568-73. [PMID: 19136019 DOI: 10.1016/j.physbeh.2008.12.007] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2008] [Revised: 11/18/2008] [Accepted: 12/10/2008] [Indexed: 11/17/2022]
Abstract
We wanted to assess the possibility that opioid activity in the central amygdala (CeA) could modulate the feeding inhibition of melanocortin stimulation of the paraventricular hypothalamus (PVN). The melanocortin system is important in both the acute regulation of satiety and feeding behavior and in the integration of long-term appetite signals. Melanotan II (MTII) is a synthetic MC3R and MC4R agonist which reduces food intake when given intracerebroventricularly (ICV) and into the PVN. Tyr-D-Ala-Gly-(me) Phe-Gly-ol (DAMGO), a micro-opioid receptor agonist, increases food intake, while opioid antagonists, like naltrexone (NTX), inhibit food intake after injection into many brain sites involved in appetite regulation, including the CeA. In food-deprived male Sprague-Dawley rats, co-injected intra-PVN MTII partially blocked the orexigenic effect of co-injected intra-CeA DAMGO. Intra-CeA NTX co-injected with intra-PVN MTII reduced food intake significantly more than either alone. NTX administered intra-CeA reduced c-Fos-immunoreactivity (IR) in nucleus accumbens neurons significantly compared to the intra-PVN MTII treated animals, animals co-injected intra-PVN with MTII and intra-CeA with NTX animals, and control animals. Intra-PVN MTII induced c-Fos-IR in significantly more PVN neurons than observed in control animals. Intra-CeA NTX co-injected with intra-PVN MTII induced c-Fos-IR significantly in PVN neurons relative to control and intra-CeA NTX animals. Such data support the significance of opioid action within the CeA as a modulator of the feeding regulation action of melanocortins within the PVN, occurring within the context of a larger appetitive network.
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MESH Headings
- Amygdala/drug effects
- Amygdala/metabolism
- Analgesics, Opioid/metabolism
- Animals
- Appetite Regulation/drug effects
- Appetite Regulation/physiology
- Drug Interactions
- Eating/drug effects
- Eating/physiology
- Enkephalin, Ala(2)-MePhe(4)-Gly(5)-/pharmacology
- Food Deprivation
- Hormones/pharmacology
- Male
- Melanocortins/metabolism
- Naltrexone/pharmacology
- Neural Pathways/physiology
- Neurotransmitter Agents/pharmacology
- Paraventricular Hypothalamic Nucleus/drug effects
- Paraventricular Hypothalamic Nucleus/metabolism
- Peptides, Cyclic/pharmacology
- Rats
- Rats, Sprague-Dawley
- Receptor, Melanocortin, Type 3/drug effects
- Receptor, Melanocortin, Type 3/metabolism
- Receptor, Melanocortin, Type 4/drug effects
- Receptor, Melanocortin, Type 4/metabolism
- Receptors, Opioid, mu/drug effects
- Receptors, Opioid, mu/metabolism
- alpha-MSH/analogs & derivatives
- alpha-MSH/pharmacology
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Affiliation(s)
- Tiffany R Beckman
- Department of Medicine, University of Minnesota, Minneapolis, MN 55455, United States.
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18
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Zhu M, Cho YK, Li CS. Activation of delta-opioid receptors reduces excitatory input to putative gustatory cells within the nucleus of the solitary tract. J Neurophysiol 2008; 101:258-68. [PMID: 19019978 DOI: 10.1152/jn.90648.2008] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The rostral nucleus of the solitary tract (NST) is the first central relay in the gustatory pathway and plays a key role in processing and modulation of gustatory information. Here, we investigated the effects of opioid receptor agonists and antagonists on synaptic responses of the gustatory parabrachial nuclei (PbN)-projecting neurons in the rostral NST to electrical stimulation of the solitary tract (ST) using whole cell recordings in the hamster brain stem slices. ST-evoked excitatory postsynaptic currents (EPSCs) were significantly reduced by met-enkephalin (MetE) in a concentration-dependent fashion and this effect was eliminated by naltrexone hydrochloride, a nonselective opioid receptor antagonist. Bath application of naltrindole hydrochloride, a selective delta-opioid receptor antagonist, eliminated MetE-induced reduction of EPSCs, whereas CTOP, a selective mu-opioid receptor antagonist had no effect, indicating that delta-opioid receptors are involved in the reduction of ST-evoked EPSCs induced by MetE. SNC80, a selective delta-opioid receptor agonist, mimicked the effect of MetE. The SNC80-induced reduction of ST-evoked EPSCs was eliminated by 7-benzylidenenaltrexone, a selective delta1-opioid receptor antagonist but not by naltriben mesylate, a selective delta2-opioid receptor antagonist, indicating that delta1-opioid receptors mediate the reduction of ST-evoked EPSCs induced by SNC80. Single-cell reverse transcriptase-polymerase chain reaction analysis revealed the presence of delta1-opioid receptor mRNA in cells that responded to SNC80 with a reduction in ST-evoked EPSCs. Moreover, Western blot analysis demonstrated the presence of 40-kDa delta-opioid receptor proteins in the rostral NST tissue. These results suggest that postsynaptic delta1-opioid receptors are involved in opioid-induced reduction of ST-evoked EPSCs of PbN-projecting rostral NST cells.
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Affiliation(s)
- Mingyan Zhu
- Department of Anatomy, Southern Illinois University School of Medicine, Life Science III Room 2073, 1135 Lincoln Dr., Carbondale, IL 62901, USA
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19
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Abstract
BACKGROUND It is well known that alcohol increases opioid activity, which can contribute to the reinforcing effect of alcohol. Clinical studies have supported reductions in alcohol consumption among alcoholic patients during treatment with opioid antagonists (OAs) and its use is recommended for this purpose. Experimental studies have demonstrated opioid receptor up-regulation after several days of OA treatment, which increases the availability of these receptors. On this basis, the physiological conditions in the period immediately after the OA treatment could increase the reinforcing value of alcohol and in this way enhance alcohol consumption. METHODS To test this hypothesis, 2 groups of Wistar male rats were used in the present study. After assessing the baseline of voluntary alcohol (10% v/v) consumption, subjects were treated with either the OA naltrexone (Ntx), (2 mg/kg/d/rat) or a saline solution (0.2 mL/d/male) for 7 days. Subsequently, all subjects were given a free choice between ethanol (10%) and water for 5 days. To study a possible cumulative effect, this procedure was sequentially repeated 4 times with each group. Water and food were available ad libitum throughout the experiment. RESULTS After each period of 7 days of Ntx use, alcohol consumption increased significantly with respect to the baseline and each equivalent period in the control group. When the subjects were exposed to alcohol again 1 week after the last of the 4 sequential periods, alcohol drinking was higher than the baseline in the Ntx group, but not in the control group. Water consumption was decreased during Ntx treatment in the control group in periods 1, 2, and 4. Food intake and body weight did not show differences between groups throughout the study; however, a decrease in food intake was observed over time regardless of treatment. CONCLUSION These results show that alcohol intake may increase after the Ntx treatment, particularly when alcohol is not available during treatment with the OA, and that this may be due to a higher availability of opioid receptors in that period.
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Affiliation(s)
- Jorge Juárez
- Laboratorio de Farmacología y Conducta, Instituto de Neurociencias, CUCBA, Universidad de Guadalajara, Guadalajara, México.
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20
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Abstract
Brainstem parasympathetic circuits that modulate digestive functions of the stomach are comprised of afferent vagal fibers, neurons of the nucleus tractus solitarius (NTS), and the efferent fibers originating in the dorsal motor nucleus of the vagus (DMV). A large body of evidence has shown that neuronal communications between the NTS and the DMV are plastic and are regulated by the presence of a variety of neurotransmitters and circulating hormones as well as the presence, or absence, of afferent input to the NTS. These data suggest that descending central nervous system inputs as well as hormonal and afferent feedback resulting from the digestive process can powerfully regulate vago-vagal reflex sensitivity. This paper first reviews the essential "static" organization and function of vago-vagal gastric control neurocircuitry. We then present data on the opioidergic modulation of NTS connections with the DMV as an example of the "gating" of these reflexes, i.e., how neurotransmitters, hormones, and vagal afferent traffic can make an otherwise static autonomic reflex highly plastic.
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21
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Appleyard SM, Bailey TW, Doyle MW, Jin YH, Smart JL, Low MJ, Andresen MC. Proopiomelanocortin neurons in nucleus tractus solitarius are activated by visceral afferents: regulation by cholecystokinin and opioids. J Neurosci 2006; 25:3578-85. [PMID: 15814788 PMCID: PMC6725389 DOI: 10.1523/jneurosci.4177-04.2005] [Citation(s) in RCA: 148] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The nucleus tractus solitarius (NTS) receives dense terminations from cranial visceral afferents, including those from the gastrointestinal (GI) system. Although the NTS integrates peripheral satiety signals and relays this signal to central feeding centers, little is known about which NTS neurons are involved or what mechanisms are responsible. Proopiomelanocortin (POMC) neurons are good candidates for GI integration, because disruption of the POMC gene leads to severe obesity and hyperphagia. Here, we used POMC-enhanced green fluorescent protein (EGFP) transgenic mice to identify NTS POMC neurons. Intraperitoneal administration of cholecystokinin (CCK) induced c-fos gene expression in NTS POMC-EGFP neurons, suggesting that they are activated by afferents stimulated by the satiety hormone. We tested the synaptic relationship of these neurons to visceral afferents and their modulation by CCK and opioids using patch recordings in horizontal brain slices. Electrical activation of the solitary tract (ST) evoked EPSCs in NTS POMC-EGFP neurons. The invariant latencies, low failure rates, and substantial paired-pulse depression of the ST-evoked EPSCs indicate that NTS POMC-EGFP neurons are second-order neurons directly contacted by afferent terminals. The EPSCs were blocked by the glutamate antagonist 2,3-dihydroxy-6-nitro-7-sulfonyl-benzo[f]quinoxaline. CCK increased the amplitude of the ST-stimulated EPSCs and the frequency of miniature EPSCs, effects attenuated by the CCK1 receptor antagonist lorglumide. In contrast, the orexigenic opioid agonists [D-Ala(2), N-Me-Phe(4), Gly-ol(5)]-enkephalin and met-enkephalin inhibited both ST-stimulated EPSCs and the frequency of miniature EPSCs. These findings identify a potential satiety pathway in which visceral afferents directly activate NTS POMC-EGFP neurons with excitatory inputs that are appropriately modulated by appetite regulators.
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Affiliation(s)
- Suzanne M Appleyard
- Department of Physiology and Pharmacology, Oregon Health and Science University, Portland, Oregon 97239-3098, USA.
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22
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Naleid AM, Grace MK, Cummings DE, Levine AS. Ghrelin induces feeding in the mesolimbic reward pathway between the ventral tegmental area and the nucleus accumbens. Peptides 2005; 26:2274-9. [PMID: 16137788 DOI: 10.1016/j.peptides.2005.04.025] [Citation(s) in RCA: 303] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/11/2005] [Revised: 04/20/2005] [Accepted: 04/20/2005] [Indexed: 11/25/2022]
Abstract
Ghrelin, a powerful orexigenic peptide released from the gut, stimulates feeding when injected centrally and has thus far been implicated in regulation of metabolic, rather than hedonic, feeding behavior. Although ghrelin's effects are partially mediated at the hypothalamic arcuate nucleus, via activation of neurons that co-express neuropeptide Y and agouti-related protein (NPY/Agrp neurons), the ghrelin receptor is expressed also in other brain sites. One of these is the ventral tegmental area (VTA), a primary node of the mesolimbic reward pathway, which sends dopaminergic projections to the nucleus accumbens (Acb), among other sites. We injected saline or three doses of ghrelin (0, 0.003, 0.03, or 0.3 nmol) into the VTA or Acb of rats. We found a robust feeding response with VTA injection of ghrelin, and a more moderate response with Acb injection. Because opioids modulate feeding in the VTA and Acb, we hypothesized that ghrelin's effects in one site were dependent on opioid signaling in the opposite site. The general opioid antagonist, naltrexone (NTX), injected into the Acb did not affect feeding elicited by ghrelin injection into the VTA, and NTX in the VTA did not affect feeding elicited by ghrelin injected into the Acb. These results suggest interaction of a metabolic factor with the reward system in feeding behavior, indicating that hedonic responses can be modulated by homeostatic factors.
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Affiliation(s)
- Amy M Naleid
- Graduate Program in Neuroscience, University of Minnesota, Minneapolis, MN 55415, USA
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23
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Kiwaki K, Kotz CM, Wang C, Lanningham-Foster L, Levine JA. Orexin A (hypocretin 1) injected into hypothalamic paraventricular nucleus and spontaneous physical activity in rats. Am J Physiol Endocrinol Metab 2004; 286:E551-9. [PMID: 14656716 DOI: 10.1152/ajpendo.00126.2003] [Citation(s) in RCA: 113] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In humans, nonexercise activity thermogenesis (NEAT) increases with positive energy balance. The mediator of the interaction between positive energy balance and physical activity is unknown. In this study, we address the hypothesis that orexin A acts in the hypothalamic paraventricular nucleus (PVN) to increase nonfeeding-associated physical activity. PVN-cannulated rats were injected with either orexin A or vehicle during the light and dark cycle. Spontaneous physical activity (SPA) was measured using arrays of infrared activity sensors and night vision videotaped recording (VTR). O(2) consumption and CO(2) production were measured by indirect calorimetry. Feeding behavior was assessed by VTR. Regardless of the time point of injection, orexin A (1 nmol) was associated with dramatic increases in SPA for 2 h after injection (orexin A: 6.27 +/- 1.95 x 10(3) beam break count, n = 24; vehicle: 1.85 +/- 1.13 x 10(3), n = 38). This increase in SPA was accompanied by compatible increase in O(2) consumption. Duration of feeding was increased only when orexin A was injected in the early light phase and accounted for only 3.5 +/- 2.5% of the increased physical activity. In a dose-response experiment, increases in SPA were correlated with dose of orexin A linearly up to 2 nmol. PVN injections of orexin receptor antagonist SB-334867 were associated with decreases in SPA and attenuated the effects of PVN-injected orexin A. Thus orexin A can act in PVN to increase nonfeeding-associated physical activity, suggesting that this neuropeptide might be a mediator of NEAT.
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Affiliation(s)
- Kohji Kiwaki
- Endocrine Research Unit, Joseph 5-194, Mayo Clinic Rochester, 200 First Street SW, Rochester, MN 55905, USA
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24
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Levine AS, Jewett DC, Cleary JP, Kotz CM, Billington CJ. Our journey with neuropeptide Y: effects on ingestive behaviors and energy expenditure. Peptides 2004; 25:505-10. [PMID: 15134869 DOI: 10.1016/j.peptides.2004.01.005] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Clark and colleagues first described the robust orexigenic effects of neuropeptide Y (NPY) in 1984. Our group as well as Stanley et al. confirmed these effects in the same year. During the next 20 years, we investigated the effects of NPY on diet preferences, opioid-related feeding, distributed neural feeding networks, energy metabolism, motivation and discriminative stimulus effects. These data together with data from other laboratories indicate that NPY increases feeding, even when rats work for food; that NPY decreases energy expenditure, particularly by altering thermogenesis; and that NPY's effects on energy metabolism are mediated by a widely distributed neural network involving other neuroregulators known to be involved in energy regulation.
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Affiliation(s)
- Allen S Levine
- Minnesota Obesity Center, Veterans Affairs Medical Center, and Department of Psychology, University of Minnesota, Minneapolis 55455, USA.
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25
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Wilson JD, Nicklous DM, Aloyo VJ, Simansky KJ. An orexigenic role for mu-opioid receptors in the lateral parabrachial nucleus. Am J Physiol Regul Integr Comp Physiol 2003; 285:R1055-65. [PMID: 14557237 DOI: 10.1152/ajpregu.00108.2003] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The pontine parabrachial nucleus (PBN) has been implicated in regulating ingestion and contains opioids that promote feeding elsewhere in the brain. We tested the actions of the selective mu-opioid receptor (mu-OR) agonist [d-Ala2,N-Me-Phe4,Gly5-ol]enkephalin (DAMGO) in the PBN on feeding in male rats with free access to food. Infusing DAMGO (0.5-4.0 nmol/0.5 microl) into the lateral parabrachial region (LPBN) increased food intake. The hyperphagic effect was anatomically specific to infusions within the LPBN, dose and time related, and selective for ingestion of chow compared with (nonnutritive) kaolin. The nonselective opioid antagonist naloxone (0.1-10.0 nmol intra-PBN) antagonized DAMGO-induced feeding, with complete blockade by 1.0 nmol and no effect on baseline. The highly selective mu-opioid antagonist d-Phe-Cys-Trp-Arg-Thr-Pen-Thr-NH2 (CTAP; 1.0 nmol) also prevented this action of DAMGO, but the kappa-antagonist nor-binaltorphimine did not. Naloxone and CTAP (10.0 nmol) decreased intake during scheduled feeding. Thus stimulating mu-ORs in the LPBN increases feeding, whereas antagonizing these sites inhibits feeding. Together, our results implicate mu-ORs in the LPBN in the normal regulation of food intake.
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Affiliation(s)
- John D Wilson
- Dept. of Pharmacology and Physiology, Drexel Univ. College of Medicine, Mailstop 488, 245 N. 15th St., Philadelphia, PA 19102-1192, USA
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26
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Thorpe AJ, Mullett MA, Wang C, Kotz CM. Peptides that regulate food intake: regional, metabolic, and circadian specificity of lateral hypothalamic orexin A feeding stimulation. Am J Physiol Regul Integr Comp Physiol 2003; 284:R1409-17. [PMID: 12736178 DOI: 10.1152/ajpregu.00344.2002] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Orexin A (OX-A) administered in the lateral hypothalamus (LH) increases feeding in a dose-dependent manner. The LH is a relatively large neural structure with a heterogeneous profile of neural inputs, efferent projections, and orexin receptor distribution. We sought to determine the LH region most sensitive to the feeding stimulatory effect of OX-A injection. Fifty-six male Sprague-Dawley rats were fitted with cannulas 1 mm above four separate LH regions approximately 1 mm apart in the rostral-caudal direction. There were 14-16 animals/LH region. After recovery, animals received either artificial cerebrospinal fluid or OX-A (250, 500, or 1,000 pmol). To determine whether there is a circadian effect of LH OX-A on the feeding response, we performed injections at 0200, 0900, 1400, and 2100. Food intake was measured at 1, 2, and 4 h after injection. The most rostral extent of the LH was the only region in which injection of OX-A significantly stimulated feeding. Within this region, feeding was increased at all times of the day, although the most robust and only significant feeding response occurred after the afternoon injection (1400) of OX-A. To determine the extent to which the metabolic status of the rat contributed to the circadian specificity of orexin-induced feeding, animals were placed on a restricted diet and injected with OX-A in the most rostral region of the LH. Under these conditions, OX-A significantly increased feeding and more robustly when compared with animals on a nonrestricted diet. These data suggest that the rostral LH is the only region of the LH sensitive to the injection of OX-A, and the metabolic status of the animal at the time of injection may influence the feeding response to OX-A.
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Affiliation(s)
- Andrew J Thorpe
- Veterans Affairs Medical Center and Minnesota Obesity Center, Minneapolis 55417, USA
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27
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Glass MJ, Briggs JE, Billington CJ, Kotz CM, Levine AS. Opioid receptor blockade in rat nucleus tractus solitarius alters amygdala dynorphin gene expression. Am J Physiol Regul Integr Comp Physiol 2002; 283:R161-7. [PMID: 12069941 DOI: 10.1152/ajpregu.00480.2001] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
It has been suggested that an opioidergic feeding pathway exists between the nucleus of the solitary tract (NTS) and the central nucleus of the amygdala. We studied the following three groups of rats: 1) artificial cerebrospinal fluid (CSF) infused in the NTS, 2) naltrexone (100 microg/day) infused for 13 days in the NTS, and 3) artificial CSF infused in the NTS of rats pair fed to the naltrexone-infused group. Naltrexone administration resulted in a decrease in body weight and food intake. Also, naltrexone infusion increased dynorphin, but not enkephalin, gene expression in the amygdala, independent of the naltrexone-induced reduction in food intake. Gene expression of neuropeptide Y in the arcuate nucleus and neuropeptide Y peptide levels in the paraventricular nucleus did not change because of naltrexone infusion. However, naltrexone induced an increase in serum leptin compared with pair-fed controls. Thus chronic administration of naltrexone in the NTS increased dynorphin gene expression in the amygdala, further supporting an opioidergic feeding pathway between these two brain sites.
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Affiliation(s)
- Michael J Glass
- Weill Medical College, Cornell University, New York, NY 10021, USA
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28
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Opioid peptides inhibit excitatory but not inhibitory synaptic transmission in the rat dorsal motor nucleus of the vagus. J Neurosci 2002. [PMID: 11943802 DOI: 10.1523/jneurosci.22-08-02998.2002] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Opioid peptides produce gastrointestinal inhibition and increase feeding when applied to the brainstem. The present studies were designed to determine the actions of opioid peptides on synaptic transmission within the dorsal motor nucleus of the vagus (DMV) and the localization of mu-opioid receptors. Whole-cell recordings were made from identified gastrointestinal-projecting DMV neurons in thin brainstem slices of the rat. Electrical stimulation of the nucleus of the tractus solitarius evoked EPSCs and IPSCs. In all neurons tested, methionine (Met)-enkephalin (0.003-30 microm) inhibited the peak amplitude of the EPSCs. The effect was prevented by naloxone (1 microm) as well as by naloxonazine (0.2 microm). An increase in the ratio of the evoked paired pulses indicated that the inhibition was attributable to actions at presynaptic receptors. This presynaptic inhibitory action was mimicked by [d-Ala(2), N-Me-Phe(4), Gly(5)-ol]-enkephalin (0.1 microm) and the analgesic dipeptide kyotorphin (10 microm) but not by cyclic[d-Pen(2), d-Pen(5)]-enkephalin (1 microm) and trans-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl]benzeneacetamide methanesulfonate (1 microm). In contrast, the amplitude of evoked IPSCs was not altered either by Met-enkephalin or by any of the opioid receptor-selective agonists. Immunohistochemical studies revealed that nerve terminals apposing DMV neurons showed immunoreactivity to mu-opioid receptors colocalized with glutamate immunoreactivity but not glutamic acid decarboxylase immunoreactivity. These results suggest that within the DMV, mu-opioid receptors are present on the nerve terminals of excitatory but not inhibitory inputs to GI motoneurons. Such specificity may imply that the central inhibitory action of opioid peptides on gastrointestinal function targets selected pathways.
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29
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Affiliation(s)
- Gerald F DiBona
- Department of Internal Medicine, University of Iowa College of Medicine and Veterans Administration Medical Center, Iowa City, Iowa 52242, USA
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30
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Abstract
The hypothalamic feeding-center model, articulated in the 1950s, held that the hypothalamus contains the interoceptors sensitive to blood-borne correlates of available or stored fuels as well as the integrative substrates that process metabolic and visceral afferent signals and issue commands to brainstem mechanisms for the production of ingestive behavior. A number of findings reviewed here, however, indicate that sensory and integrative functions are distributed across a central control axis that includes critical substrates in the basal forebrain as well as in the caudal brainstem. First, the interoceptors relevant to energy balance are distributed more widely than had been previously thought, with a prominent brainstem complement of leptin and insulin receptors, glucose-sensing mechanisms, and neuropeptide mediators. The physiological relevance of this multiple representation is suggested by the demonstration that similar behavioral effects can be obtained independently by stimulation of respective forebrain and brainstem subpopulations of the same receptor types (e.g., leptin, CRH, and melanocortin). The classical hypothalamic model is also challenged by the integrative achievements of the chronically maintained, supracollicular decerebrate rat. Decerebrate and neurologically intact rats show similar discriminative responses to taste stimuli and are similarly sensitive to intake-inhibitory feedback from the gut. Thus, the caudal brainstem, in neural isolation from forebrain influence, is sufficient to mediate ingestive responses to a range of visceral afferent signals. The decerebrate rat, however, does not show a hyperphagic response to food deprivation, suggesting that interactions between forebrain and brainstem are necessary for the behavioral response to systemic/ metabolic correlates of deprivation in the neurologically intact rat. At the same time, however, there is evidence suggesting that hypothalamic-neuroendocrine responses to fasting depend on pathways ascending from brainstem. Results reviewed are consistent with a distributionist (as opposed to hierarchical) model for the control of energy balance that emphasizes: (i) control mechanisms endemic to hypothalamus and brainstem that drive their unique effector systems on the basis of local interoceptive, and in the brainstem case, visceral, afferent inputs and (ii) a set of uni- and bidirectional interactions that coordinate adaptive neuroendocrine, autonomic, and behavioral responses to changes in metabolic status.
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Affiliation(s)
- Harvey J Grill
- Graduate Group of Psychology, University of Pennsylvania, Philadelphia, 19104, USA
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31
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Abstract
This paper is the twenty-third installment of the annual review of research concerning the opiate system. It summarizes papers published during 2000 that studied the behavioral effects of the opiate peptides and antagonists, excluding the purely analgesic effects, although stress-induced analgesia is included. The specific topics covered this year include stress; tolerance and dependence; learning, memory, and reward; eating and drinking; alcohol and other drugs of abuse; sexual activity, pregnancy, and development; mental illness and mood; seizures and other neurological disorders; electrical-related activity; general activity and locomotion; gastrointestinal, renal, and hepatic function; cardiovascular responses; respiration and thermoregulation; and immunological responses.
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Affiliation(s)
- A L Vaccarino
- Department of Psychology, University of New Orleans, New Orleans, LA 70148, USA.
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32
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Hagan MM, Rushing PA, Benoit SC, Woods SC, Seeley RJ. Opioid receptor involvement in the effect of AgRP- (83-132) on food intake and food selection. Am J Physiol Regul Integr Comp Physiol 2001; 280:R814-21. [PMID: 11171662 DOI: 10.1152/ajpregu.2001.280.3.r814] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Agouti-related peptide (AgRP) is a receptor antagonist of central nervous system (CNS) melanocortin receptors and appears to have an important role in the control of food intake since exogenous CNS administration in rats and overexpression in mice result in profound hyperphagia and weight gain. Given that AgRP is heavily colocalized with neuropeptide Y (NPY) and that orexigenic effects of NPY depend on activity at opioid receptors, we hypothesized that AgRP's food-intake effects are also mediated by opioid receptors. Subthreshold doses of the opioid receptor antagonist naloxone blocked AgRP-induced intake when given simultaneously but not 24 h after AgRP injection. Opioids not only influence food intake but food selection as well. Hence, we tested AgRP's effect to alter food choice between matched diets with differing dietary fat content. AgRP selectively enhanced intake of the high-fat but not the low-fat diet. Additionally, AgRP selectively increased chow intake in rats given ad libitum access to a 20% sucrose solution and standard rat chow. The current results indicate that AgRP influences not only caloric intake but food selection as well and that the early effects of AgRP depend critically on an interaction with opioid receptors.
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Affiliation(s)
- M M Hagan
- Department of Psychology, University of Alabama at Birmingham, Birmingham, Alabama 35294-1170, USA
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Glass MJ, Billington CJ, Levine AS. Naltrexone administered to central nucleus of amygdala or PVN: neural dissociation of diet and energy. Am J Physiol Regul Integr Comp Physiol 2000; 279:R86-92. [PMID: 10896868 DOI: 10.1152/ajpregu.2000.279.1.r86] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
There is evidence that opioids may affect food consumption through mechanisms as diverse as reward or energy metabolism. However, these hypotheses are derived from studies employing peripheral or, more rarely, intracerebroventricular administration of drugs. Opioid receptors have a wide distribution in the central nervous system and include a number of regions implicated in food intake such as the hypothalamic paraventricular nucleus (PVN) and the central nucleus of the amygdala (ACe). It is not known whether local opioid receptor blockade in either of these regions will produce similar effects on food intake. To examine this issue, a chronic cannula was aimed at either the PVN or ACe of rats that were fed a choice of a high-fat and high-carbohydrate diet, which allows for the measurement of both preference and total energy consumption. Naltrexone influenced preferred and nonpreferred food consumption, depending on the site of administration. Consumption of both preferred and nonpreferred diets was suppressed after PVN naltrexone administration, whereas only preferred diet intake was reduced after ACe injection of naltrexone. The present evidence indicates that direct stimulation of different brain regions with naltrexone may be associated with diverse effects on diet selection, which may be accounted for by manipulation of specific functional neural circuitry.
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Affiliation(s)
- M J Glass
- Minnesota Obesity Center, Departments of Psychiatry, Psychology, and Medicine, Veterans Affairs Medical Center and the University of Minnesota, Minneapolis, Minnesota, 55417, USA
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