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Kirk SL, Samuelsson AM, Argenton M, Dhonye H, Kalamatianos T, Poston L, Taylor PD, Coen CW. Maternal obesity induced by diet in rats permanently influences central processes regulating food intake in offspring. PLoS One 2009; 4:e5870. [PMID: 19516909 PMCID: PMC2690656 DOI: 10.1371/journal.pone.0005870] [Citation(s) in RCA: 264] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2009] [Accepted: 05/12/2009] [Indexed: 01/21/2023] Open
Abstract
Hypothalamic systems which regulate appetite may be permanently modified during early development. We have previously reported hyperphagia and increased adiposity in the adult offspring of rodents fed an obesogenic diet prior to and throughout pregnancy and lactation. We now report that offspring of obese (OffOb) rats display an amplified and prolonged neonatal leptin surge, which is accompanied by elevated leptin mRNA expression in their abdominal white adipose tissue. At postnatal Day 30, before the onset of hyperphagia in these animals, serum leptin is normal, but leptin-induced appetite suppression and phosphorylation of STAT3 in the arcuate nucleus (ARC) are attenuated; the level of AgRP-immunoreactivity in the hypothalamic paraventricular nucleus (PVH), which derives from neurones in the ARC and is developmentally dependent on leptin, is also diminished. We hypothesise that prolonged release of abnormally high levels of leptin by neonatal OffOb rats leads to leptin resistance and permanently affects hypothalamic functions involving the ARC and PVH. Such effects may underlie the developmental programming of hyperphagia and obesity in these rats.
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Affiliation(s)
- Shona L. Kirk
- Division of Reproduction and Endocrinology, King's College London, London, United Kingdom
| | - Anne-Maj Samuelsson
- Division of Reproduction and Endocrinology, King's College London, London, United Kingdom
| | - Marco Argenton
- Division of Reproduction and Endocrinology, King's College London, London, United Kingdom
| | - Hannah Dhonye
- Division of Reproduction and Endocrinology, King's College London, London, United Kingdom
| | - Theodosis Kalamatianos
- Division of Reproduction and Endocrinology, King's College London, London, United Kingdom
| | - Lucilla Poston
- Division of Reproduction and Endocrinology, King's College London, London, United Kingdom
| | - Paul D. Taylor
- Division of Reproduction and Endocrinology, King's College London, London, United Kingdom
| | - Clive W. Coen
- Division of Reproduction and Endocrinology, King's College London, London, United Kingdom
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The vagus nerve, food intake and obesity. ACTA ACUST UNITED AC 2008; 149:15-25. [PMID: 18482776 DOI: 10.1016/j.regpep.2007.08.024] [Citation(s) in RCA: 211] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2006] [Accepted: 08/08/2007] [Indexed: 01/01/2023]
Abstract
Food interacts with sensors all along the alimentary canal to provide the brain with information regarding its composition, energy content, and beneficial effect. Vagal afferents innervating the gastrointestinal tract, pancreas, and liver provide a rapid and discrete account of digestible food in the alimentary canal, as well as circulating and stored fuels, while vagal efferents, together with the sympathetic nervous system and hormonal mechanisms, codetermine the rate of nutrient absorption, partitioning, storage, and mobilization. Although vagal sensory mechanisms play a crucial role in the neural mechanism of satiation, there is little evidence suggesting a significant role in long-term energy homeostasis. However, increasing recognition of vagal involvement in the putative mechanisms making bariatric surgeries the most effective treatment for obesity should greatly stimulate future research to uncover the many details regarding the specific transduction mechanisms in the periphery and the inter- and intra-neuronal signaling cascades disseminating vagal information across the neuraxis.
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Nillni EA. Regulation of prohormone convertases in hypothalamic neurons: implications for prothyrotropin-releasing hormone and proopiomelanocortin. Endocrinology 2007; 148:4191-200. [PMID: 17584972 DOI: 10.1210/en.2007-0173] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Recent evidence demonstrated that posttranslational processing of neuropeptides is critical in the pathogenesis of obesity. Leptin or other physiological changes affects the biosynthesis and processing of many peptides hormones as well as the regulation of the family of prohormone convertases responsible for the maturation of these hormones. Regulation of energy balance by leptin involves regulation of several proneuropeptides such as proTRH and proopiomelanocortin. These proneuropeptide precursors require for their maturation proteolytic cleavage by the prohormone convertases 1 and 2 (PC1/3 and PC2). Because biosynthesis of mature peptides in response to leptin requires prohormone processing, it is hypothesized that leptin might regulate hypothalamic PC1/3 and PC2 expression, ultimately leading to coordinated processing of prohormones into mature peptides. Leptin has been shown to increase PC1/3 and PC2 promoter activities, and starvation of rats, leading to low serum leptin levels, resulted in a decrease in PC1/3 and PC2 gene and protein expression in the paraventricular and arcuate nucleus of the hypothalamus. Changes in nutritional status also changes proopiomelanocortin processing in the nucleus of the solitary tract, but this is not reversed by leptin. The PCs are also physiologically regulated by states of hyperthyroidism, hyperglycemia, inflammation, and suckling, and a recently discovered nescient helix-loop-helix-2 transcription factor is the first one to show an ability to regulate the transcription of PC1/3 and PC2. Therefore, the coupled regulation of proneuropeptide/processing enzymes may be a common process, by which cells generate more effective processing of prohormones into mature peptides.
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Affiliation(s)
- Eduardo A Nillni
- Division of Endocrinology, Department of Medicine, Brown Medical School/Rhode Island Hospital, 55 Claverick Street, Third floor, Room 320, Providence, Rhode Island 02903, USA.
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Perello M, Stuart RC, Nillni EA. Differential effects of fasting and leptin on proopiomelanocortin peptides in the arcuate nucleus and in the nucleus of the solitary tract. Am J Physiol Endocrinol Metab 2007; 292:E1348-57. [PMID: 17227963 DOI: 10.1152/ajpendo.00466.2006] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The alpha-melanocyte-stimulating hormone (alpha-MSH), derived from proopiomelanocortin (POMC), is generated by a posttranslational processing mechanism involving the prohormone convertases (PCs) PC1/3 and PC2. In the brain, alpha-MSH is produced in the arcuate nucleus (ARC) of the hypothalamus and in the nucleus of the solitary tract (NTS) of the medulla. This peptide is key in controlling energy balance, as judged by changes observed at transcriptional level. However, little information is available regarding the biosynthesis of the precursor POMC and the production of its processed peptides during feeding, fasting, and fasting plus leptin in the ARC compared with the NTS in conjunction with the PC activity. In this study we found that, in the ARC, pomc mRNA, POMC-derived peptides, and PC1/3 all decreased during fasting, and administration of leptin reversed these effects. In contrast, in the NTS, where there is a large amount of a 28.1-kDa peptide similar in size to POMC, the 28.1-kDa peptide and other POMC-derived peptides, including alpha-MSH, were further accumulated in fasting conditions, whereas pomc mRNA decreased. These changes were not reversed by leptin. We also observed that, during fasting, PC2 levels decreased in the NTS. These data suggest that, in the NTS, fasting induced changes in POMC biosynthesis, and processing is independent of leptin. These observations indicate that changes in energy status affect POMC in the brain in a tissue-specific manner. This represents a novel aspect in the regulation of energy balance and may have implications in the pathophysiology of obesity.
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Affiliation(s)
- Mario Perello
- Division of Endocrinology, Department of Medicine, Brown University, Rhode Island Hospital, Providence, Rhode Island 02903, USA
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Abstract
The central melanocortin system plays a key role in the regulation of energy homeostasis. Neurons containing the peptide precursor proopiomelanocortin (POMC) are found at two sites in the brain, the arcuate nucleus of the hypothalamus (ARC) and the caudal region of the nucleus of the solitary tract (NTS). ARC POMC neurons, which also express cocaine- and amphetamine-regulated transcript (CART), are known to mediate part of the response to factors regulating energy homeostasis, such as leptin and ghrelin. In contrast, the physiological role(s) of the POMC neurons in the caudal brainstem are not well characterized. However, development of a transgenic mouse expressing green fluorescent protein under the control of the POMC promoter [POMC-enhanced green fluorescent protein (EGFP) mouse] has aided the study of these neurons. Indeed, recent studies have shown significant activation of NTS POMC-EGFP cells by the gut released satiety factor cholecystokinin (CCK). Here we show that peripheral leptin administration induces the expression of phospho-signal transducer and activator of transcription 3 immunoreactivity (pSTAT3-IR), a marker of leptin receptor signaling, in more than 50% of NTS POMC-EGFP neurons. Furthermore, these POMC-EGFP neurons comprise 30% of all pSTAT3-IR cells in the NTS. Additionally, we also show that in contrast to the ARC population, NTS POMC-EGFP neurons do not coexpress CART immunoreactivity. These data suggest that NTS POMC neurons may participate with ARC POMC cells in mediating some of the effects of leptin and thus comprise a novel cell group regulated by both long-term adipostatic signals and satiety factors such as CCK.
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Affiliation(s)
- Kate L J Ellacott
- Center for the Study of Weight Regulation and Associated Disorders and Vollum Institute, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, 97239-3098, USA
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Schuhler S, Ebling FJP. Role of melanocortin in the long-term regulation of energy balance: lessons from a seasonal model. Peptides 2006; 27:301-9. [PMID: 16269204 DOI: 10.1016/j.peptides.2005.03.060] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/30/2004] [Accepted: 03/18/2005] [Indexed: 11/29/2022]
Abstract
Siberian hamsters express photoperiod-regulated seasonal cycles of body weight and food intake, providing an opportunity to study the role of melanocortin systems in regulating long-term adaptive changes in energy metabolism. These hamsters accumulate intraperitoneal fat reserves when kept in long summer photoperiods, but show a profound long-term decrease in food intake and body weight when exposed to a short winter photoperiod. Icv administration of a MC3/4-R agonist (MTII) potently suppresses food intake in hamsters in both the obese and lean state, indicating the potential for melanocortin systems to regulate energy metabolism in the hypothalamus of the Siberian hamster. Icv treatment with the melanocortin antagonist SHU9119 increases food intake in both seasonal states. Moreover, hamsters bearing neurotoxic lesions, which destroy the majority of POMC expressing neurons in the arcuate nucleus are still able to show seasonal regulation of body weight. These studies in a seasonal model substantiate the view that endogenous melanocortin systems exert a tonic inhibition of food intake in mammals. The observations that this melanocortin tone occurs to a similar extent in both an anabolic state induced by a long day photoperiod, and in a catabolic state induced by a short day photoperiod, suggests that alterations in endogenous melanocortin tone are not the primary cause of the lipolysis, weight-loss and hypophagia which characterize the establishment of the short day-induced overwintering state.
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Affiliation(s)
- Sandrine Schuhler
- School of Biomedical Sciences, University of Nottingham Medical School, Queens Medical Centre, Nottingham NG7 2UH, UK.
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7
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Cone RD. Anatomy and regulation of the central melanocortin system. Nat Neurosci 2005; 8:571-8. [PMID: 15856065 DOI: 10.1038/nn1455] [Citation(s) in RCA: 1087] [Impact Index Per Article: 57.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2005] [Accepted: 03/15/2005] [Indexed: 12/12/2022]
Abstract
The central melanocortin system is perhaps the best-characterized neuronal pathway involved in the regulation of energy homeostasis. This collection of circuits is unique in having the capability of sensing signals from a staggering array of hormones, nutrients and afferent neural inputs. It is likely to be involved in integrating long-term adipostatic signals from leptin and insulin, primarily received by the hypothalamus, with acute signals regulating hunger and satiety, primarily received by the brainstem. The system is also unique from a regulatory point of view in that it is composed of fibers expressing both agonists and antagonists of melanocortin receptors. Given that the central melanocortin system is an active target for development of drugs for the treatment of obesity, diabetes and cachexia, it is important to understand the system in its full complexity, including the likelihood that the system also regulates the cardiovascular and reproductive systems.
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Affiliation(s)
- Roger D Cone
- Vollum Institute and the Center for the Study of Weight Regulation, Oregon Health and Science University, 3181 SW Sam Jackson Park Road, Portland, Oregon 97239, USA.
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Rónai AZ, Kató E, Al-Khrasani M, Hajdú M, Müllner K, Elor G, Gyires K, Fürst S, Palkovits M. Age and monosodium glutamate treatment cause changes in the stimulation-induced [3H]-norepinephrine release from rat nucleus tractus solitarii-dorsal vagal nucleus slices. Life Sci 2004; 74:1573-80. [PMID: 14738902 DOI: 10.1016/j.lfs.2003.05.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
In nucleus tractus solitarii-dorsal vagal nucleus slices prepared from young adult rats (180-260 g) 10(-3) M L-glutamate and 10(-5) M baclofen caused a 2-3-fold increase of field stimulation-induced [3H]-norepinephrine release without affecting the resting release. In slices prepared from rats treated neonatally with monosodium glutamate neither L-glutamate nor baclofen had any effect on stimulation-induced norepinephrine release, tested between postnatal days 74-99 (350-530 g). In untreated littermates used in the same period (460-580 g) L-glutamate was fully effective whereas baclofen was ineffective. The tritium content in tissue extracts did not differ significantly in the three experimental groups. It is concluded that i) the loss of GABA(B) receptor-mediated disinhibitory stimulation of norepinephrine release is an age-related phenomenon and ii) neonatal monosodium glutamate treatment causes a damage in the local neural circuitry characterized by the loss of glutamate receptor-mediated mechanism that stimulates the release of norepinephrine.
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Affiliation(s)
- András Z Rónai
- Department of Pharmacology and Pharmacotherapy, Semmelweis University, P.O. Box 370, H-1445 Budapest, Hungary.
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Rónai AZ, Gyires K, Barna I, Müllner K, Palkovits M. Neonatal monosodium glutamate treatment abolishes both delta opioid receptor-induced and alpha-2 adrenoceptor-mediated gastroprotection in the lower brainstem in rats. JOURNAL OF PHYSIOLOGY, PARIS 2001; 95:215-20. [PMID: 11595440 DOI: 10.1016/s0928-4257(01)00028-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Neonatal monosodium glutamate treatment reduced immunoreactive beta-endorphin content in the mediobasal hypothalamus by 50% in adult, male Wistar rats as compared to hypertonic saline-treated littermates; there was also a moderate (approx. 25%) reduction in the rostral part of the nucleus of the solitary tract. In sham-treated adults the intracisternally injected alpha-2 adenoceptor stimulant clonidine (0.47 nmol/rat) and the delta opioid receptor type agonist (D-Ala(2), D-Leu(5))-enkephalin (0.8 nmol/rat) reduced acidified ethanol-induced mucosal lesions in the stomach by 84.1 and 77.5%, respectively, whereas the same doses were completely ineffective in rats treated neonatally by monosodium glutamate. The data taken together with the results of previous studies with the same substances in rats with retroarcuate knife cuts suggest that neuronal damage in the nucleus of the solitary tract region rather than in the arcuate nucleus is responsible for the changes seen in the pharmacological responsiveness.
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Affiliation(s)
- A Z Rónai
- Department of Pharmacology and Pharmacotherapy, Semmelweis University, Nagyvárad tér 4, H-1089 Budapest, Hungary.
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Lin JY, Pan JT. Single-unit activity of dorsomedial arcuate neurons and diurnal changes of tuberoinfundibular dopaminergic neuron activity in female rats with neonatal monosodium glutamate treatment. Brain Res Bull 1999; 48:103-8. [PMID: 10210175 DOI: 10.1016/s0361-9230(98)00153-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Neonatal monosodium glutamate (MSG)-treated rats were used in this study to answer two questions: (1) whether or not the dopamine-responsive dorsomedial arcuate (dm-ARN) neurons are tuberoinfundibular dopaminergic (TIDA) neurons, and (2) whether or not the remaining TIDA neurons in MSG-treated rats are functioning normally. MSG (4 mg/g b. wt., subcutaneously [s.c.]) or saline was given to neonatal Sprague-Dawley rats on days 1, 3, 5, 7, and 9 after birth. The female rats were ovariectomized at 50 days of age and treated with estrogen for 1 week before they were used between 65-90 days of age. The tyrosine hydroxylase-immunoreactive (TH-ir) neurons located in the dm and ventrolateral (vl) parts of the ARN were significantly reduced in MSG-treated rats, as determined by immunohistochemical method. Some TH-ir cells, however, were visible along the border of the third ventricle. Using single-unit recording in brain slices, we found that dopamine inhibited significantly fewer percentage of dm-ARN neurons in MSG-treated (28.2%, n = 39) than in saline-treated rats (73.3%, n = 15). In contrast, bombesin exhibited similar effects (over 70% excitation) in both groups. Using neurochemical means, neonatal MSG treatment produced significant decreases of both 3,4-dihydroxyphenylacetic acid and dopamine levels, but not their ratios, in the median eminence. Moreover, the diurnal change of TIDA neuronal activity persisted in the MSG-treated rats; so did the estrogen-induced afternoon prolactin surge. All these results indicate that neonatal MSG-treatment reduced the number and altered the location of TIDA and dopamine-responsive dm-ARN neurons. The remaining TIDA neurons seemed to be able to maintain their basal activities and diurnal rhythm.
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Affiliation(s)
- J Y Lin
- Department of Medical Technology, Chung-Tai Institute of Medical Science and Technology, Taichung, Taiwan
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11
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Brainstem application of melanocortin receptor ligands produces long-lasting effects on feeding and body weight. J Neurosci 1998. [PMID: 9822766 DOI: 10.1523/jneurosci.18-23-10128.1998] [Citation(s) in RCA: 203] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Recent evidence suggests that the central melanocortin (MC) system is a prominent contributor to food intake and body weight control. MC receptor (MC-R) populations in the arcuate and paraventricular nuclei are considered probable sites of action mediating the orexigenic effects of systemically or intracerebroventricularly administered ligands. Yet, the highest MC4-R density in the brain is found in the dorsal motor nucleus of the vagus nerve, situated subjacent to the commissural nucleus of the solitary tract, a site of pro-opiomelanocortin mRNA expression. We evaluated the contribution of the caudal brainstem MC system by (1) performing respective dose-response analyses for an MC-R agonist (MTII) and antagonist (SHU9119) delivered to the fourth ventricle, (2) comparing, in the same rats, the fourth intracerebroventricular dose-response profiles to those obtained with lateral intracerebroventricular delivery, and (3) delivering an effective dose of MTII or SHU9119 to rats before a 24 hr period of food deprivation. Fourth intracerebroventricular agonist treatment yielded a dose-dependent reduction of short-term (2 and 4 hr) and longer-term (24 hr) food intake and body weight. Fourth intracerebroventricular antagonist treatment produced the opposite pattern of results: dose-related increases in food intake and corresponding increases in body weight change for the 24-96 hr observation period. Comparable dose-response functions for food intake and body weight were observed when these compounds were delivered to the lateral ventricle. Results from deprived rats (no effect of MTII or SHU9119 on weight loss) support the impression derived from the dose-response analyses that the body weight change that follows MC treatments is secondary to their respective effects on food intake. Results support the relevance of the brainstem MC-R complement to the control of feeding.
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Ebling FJ, Arthurs OJ, Turney BW, Cronin AS. Seasonal neuroendocrine rhythms in the male Siberian hamster persist after monosodium glutamate-induced lesions of the arcuate nucleus in the neonatal period. J Neuroendocrinol 1998; 10:701-12. [PMID: 9744488 DOI: 10.1046/j.1365-2826.1998.00253.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The aim of these experiments was to examine the role of the arcuate nucleus in the control of seasonal cycles of body weight, feed intake, moulting and reproduction in the Siberian hamster. The arcuate nucleus has previously been implicated as a central site where systemic feedback signals (e.g. leptin) might act to regulate feed intake and body weight, so it was predicted that hamsters with lesions of this structure would be unable to display the inhibitory effects of short days on these parameters. In the first series of studies, lesions that destroyed approximately 80% of the cells in the arcuate nucleus were produced by treating hamsters neonatally with monosodium glutamate (MSG; 4 mg/g body weight sc), and vehicle- and MSG-treated males were raised from birth in long days (LD) or short days (SD). In hamsters raised in LD, the initial gain in body weight and testicular growth were significantly reduced by MSG treatment, however, growth rate and testis weight were still significantly greater than in vehicle- or MSG-treated hamsters raised in SD. In the second study, hamsters treated neonatally with vehicle or MSG were raised in LD for 8 weeks and, subsequently, approximately half in each group were transferred to SD for 18 weeks. As expected, vehicle-treated hamsters showed a characteristic decline in body weight when exposed to SD, while those remaining in LD continued to increase body weight. Feed intake decreased in parallel with the decline in body weight in SD, a complete moult to the white winter pelage occurred by 16 weeks in SD, and testicular regression occurred. Responses to SD also occurred in the MSG-treated hamsters: body weight decreased in SD but increased in their lesioned litter mates remaining in LD, and feed intake paralleled body weight changes in these groups. The moult to winter pelage was significantly retarded in MSG-treated hamsters transferred to SD. The testes were completely regressed in sham- and MSG-treated hamsters exposed to SD, whereas testes weights in MSG-treated hamsters maintained in LD were intermediate between those in vehicle-treated hamsters in SD and LD. Thus, despite initial effects on growth, the MSG-treated hamsters bearing substantial lesions of the arcuate nucleus were able to show appropriate responses to photoperiod, although not always of the same magnitude as the unlesioned controls. We conclude that feedback mechanisms operating via the arcuate nucleus are not the major regulators of seasonal cycles of body weight, feed intake, pelage and reproduction.
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Affiliation(s)
- F J Ebling
- Department of Anatomy, University of Cambridge, Downing Site, UK
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Abstract
Efferent projections of the commissural nucleus tractus solitarius (cNTS0 in the region containing opiocortin-immunoreactive (-IR) neurons were identified using Phaseolus vulgaris leucoagglutinin (PHA-L). Efferents were identified in the bed nucleus of the stria terminalis, preoptic area, amygdala, hypothalamus, periaqueductal gray, parabrachial nucleus, locus coeruleus, medullary catecholaminergic groups, and NTS. The PHA-L-IR varicosities in lateral parabrachial nucleus were identified in close association with CRF-IR and enkephalin-IR cells. These data on cNTS projections are consistent with our previous immunocytochemical and lesion studies on opiocortin connectivity and provide anatomical evidence that neurons in the cNTS may influence cardiovascular and sympathetic nervous system function via connectivity with nuclei in the lateral brain stem.
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Affiliation(s)
- L J Sim
- Neuroendocrine Unit, University of Rochester School of Medicine and Dentistry, NY 14642
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Phelix CF, Hartle DK. Systemic glutamate induces degeneration of a subpopulation of tyrosine hydroxylase-immunoreactive neurons in the rat area postrema. Brain Res 1990; 516:335-40. [PMID: 1973067 DOI: 10.1016/0006-8993(90)90938-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Neuronal damage in the area postrema (AP) of 12-14-week-old male rats was induced by subcutaneous administration of monosodium glutamate (MSG). An immunocytochemical method was used to visualize catecholaminergic neurons in the AP after MSG-treatment. Some tyrosine hydroxylase-immunoreactive neurons exhibited marked signs of degeneration, while others appeared undamaged. We conclude that catecholamine-synthesizing neurons in the AP are differentially sensitive to the neuroexcitotoxic effect of systemic glutamate.
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Affiliation(s)
- C F Phelix
- Department of Pharmacology and Toxicology, College of Pharmacy, University of Georgia, Athens 30602
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Joseph SA, Michael GJ. Efferent ACTH-IR opiocortin projections from nucleus tractus solitarius: a hypothalamic deafferentation study. Peptides 1988; 9:193-201. [PMID: 2834701 DOI: 10.1016/0196-9781(88)90027-7] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The distribution of opiocortin (OR-ir) immunoreactive fibers was examined immunocytochemically throughout the brain in rats following surgical isolation of the arcuate opiocortin-ir neuronal pool in the medial basal hypothalamus (MBH). Fibers which emanate from this pool were completely severed and thus eliminated from the rest of the brain, leaving intact those which can be identified immunocytochemically as opiocortin-ir projections from the medullary pool located in the nucleus tractus solitarius (NTS). These studies reveal a unique organizational pattern of proopiomelanocortin (POMC) peptidergic neuronal systems and demonstrate that several pontine and medullary regions receive projections from both the hypothalamic (arcuate) and medullary (NTS) opiocortin-ir perikarya. Comparative analyses of deafferented and control brains reveal that certain brainstem autonomic centers such as parabrachial (PB), locus coeruleus (LC), nucleus paragiganticellularis (PGi) are recipients of fibers which emanate from both arcuate and NTS opiocortin-ir perikarya. Areas which receive projections from arcuate opiocortin-ir neurons alone include forebrain and hypothalamic nuclei as well as the periaqueductal grey.
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Affiliation(s)
- S A Joseph
- Neuroendocrine Unit, University of Rochester, School of Medicine and Dentistry, NY 14642
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Palkovits M, Mezey E, Eskay RL. Pro-opiomelanocortin-derived peptides (ACTH/beta-endorphin/alpha-MSH) in brainstem baroreceptor areas of the rat. Brain Res 1987; 436:323-38. [PMID: 2829991 DOI: 10.1016/0006-8993(87)91676-3] [Citation(s) in RCA: 121] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Relatively high concentrations of adrenocorticotropic hormone (ACTH), beta-endorphin and alpha-melanocyte-stimulating hormone (alpha-MSH) were determined by radioimmunoassay in the nucleus of the solitary tract (NTS) of rats. Dense networks of immunoreactive fibers for these peptides were most prominent in the commissural part of the nucleus, where immunostained perikarya (8-15 per section) were also seen in colchicine-treated rats. Moderate peptide levels and moderately dense immunoreactive networks of these peptides were found in the lateral reticular nucleus (including the A1 and A5-C1 catecholaminergic cell groups) and the nucleus ambiguus. Ten different types of surgical lesions or transections were performed in the hypothalamus and the lower brainstem to determine the origin of ACTH, beta-endorphin and alpha-MSH in the brainstem baroreceptor centers. Except the commissural part of the NTS, the baroreceptor areas receive ACTH, beta-endorphin and alpha-MSH innervations from both the hypothalamic arcuate cells and local neurons in the NTS. Fibers in the commissural part of the NTS seem to be of local origin. Hypothalamic fibers to the rostral part of the NTS and the vasomotor A5-C1 cell groups descend in both a medial (through the periaqueductal central gray) and a lateral (ventrolateral tegmental fibers) pathway, whereas fibers to the caudal lateral reticular nucleus (A1 cell group) and the nucleus ambiguus may run only in the lateral pathway. The descending fibers may decussate somewhere in the caudal hypothalamus-rostral midbrain, but caudal to that level they run and terminate ipsilaterally. Fibers from the ACTH-, beta-endorphin- and alpha-MSH-containing cells in the NTS form a bundle arching between the NTS and the ventrolateral medulla and partially (40-55%) innervate the vasomotor and the vasodepressor areas, as well as the nucleus ambiguus.
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Affiliation(s)
- M Palkovits
- Laboratory of Cell Biology, National Institute of Mental Health, Bethesda, MD 20892
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Abstract
Unilateral microinjections of alpha-MSH (0.3, 1.2 and 12 pmol) into the nucleus tractus solitarius (NTS) of urethane-anaesthetized rats did not modify blood pressure or heart rate (HR). Using a dual microinjection technique, it has been shown that prior injection of alpha-MSH (0.3 pmol) attenuated the pressor effect of a similar injection of dynorphin 1-9 (18 pmol) but did not modify the cardiovascular effects of [Met]enkephalin (14 pmol). Since alpha-MSH has been localized in the NTS, the results indicate that this peptide may play a role in central cardiovascular control, possibly acting in an antagonistic manner to the endogenous opioid peptides.
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Affiliation(s)
- D A Carter
- Medical Unit, Charing Cross and Westminster Medical School, Westminster Hospital, London, England
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Palkovits M, Eskay RL. Distribution and possible origin of beta-endorphin and ACTH in discrete brainstem nuclei of rats. Neuropeptides 1987; 9:123-37. [PMID: 3033542 DOI: 10.1016/0143-4179(87)90051-5] [Citation(s) in RCA: 68] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Immunoreactive ACTH and beta-endorphin in the lower brainstem nuclei of intact and brainstem-hemisected rats were quantified by radioimmunoassay. The distribution of these peptides was almost identical throughout the lower brainstem. The concentrations of ACTH and beta-endorphin were essentially equal when expressed on a molar basis. Both peptides were distributed unevenly in the lower brainstem. High concentrations were found in the periaqueductal central gray matter and the dorsal raphe nucleus, and moderate levels were present in the locus coeruleus, the parabrachial nuclei, the nucleus raphe magnus and in the nucleus of the solitary tract. beta-Endorphin was measurable in all 43 brainstem nuclei investigated; ACTH was non-detectable in the red and lateral cuneate nuclei. Except in certain areas in the medulla oblongata (nucleus of the solitary tract, lateral reticular nucleus, reticular formation) ACTH and beta-endorphin declined in brainstem nuclei 10 days after midbrain hemisections. Retrograde accumulation of ACTH and beta-endorphin was found in the arcuate nucleus 3 days after midbrain hemisection, which was mainly ipsilateral to the lesion. Data from brainstem-hemisected rats also indicated that ACTH and beta-endorphin in the nucleus of the solitary tract are primarily of local origin, whereas the lateral reticular nucleus (A1 and A5 catecholaminergic cell groups) and medullary reticular formation may receive ACTH and beta-endorphin innervation from both hypothalamic and medullary neurons.
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