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Routh VH, Horwitz BA, Gietzen DW, Stern JS. Hypothalamic Monoaminergic Activity in 11-Week-Old Cold-Exposed Female Lean(Fa/Fa)and Obese(fa/fa)Zucker Rats. ACTA ACUST UNITED AC 2012; 2:28-37. [PMID: 16355483 DOI: 10.1002/j.1550-8528.1994.tb00041.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
We previously reported that serotonergic activity was reduced in the ventromedial hypothalamic nucleus (VMN) of obese vs. lean male Zucker rats. To verify that this reduction was associated with genotype rather than gender, we measured monoamines and their major metabolites in hypothalamic nuclei of 11-week-old female lean (Fa/Fa) and obese (fa/fa) Zucker rats. In addition, since the thermic response to cold is reported to differ between lean and obese rats, some rats were also exposed to 9 degrees or 22 degrees C for 2h to determine if cold exposure altered hypothalamic monoaminergic activity. As in males, levels of 5-hydroxyindoleacetic acid [5-HIAA; major metabolite of serotonin (5-HT)] and the ratio of 5-HIAA/5-HT were lower in the VMN of obese vs. lean females (P = 0.008, 0.001, respectively). 5-HIAA/5-HT was also reduced in the paraventricular (PVN) and suprachiasmatic nuclei (SCN) of the obese compared to the lean females. Cold exposure significantly stimulated brown fat mitochondrial GDP binding in lean but not obese rats. Similarly, levels of norepinephrine, dopamine (DA), 5-HIAA, and 5-HT in the PVN, and 5-HIAA in the SCN increased in cold-exposed lean but not obese rats. In contrast, VMN and preoptic 3,4-dihydroxyphenylacetic acid (DOPAC; major metabolite of DA) increased in the cold-exposed obese but not lean animals. We conclude that: (1) the blunted peripheral response to cold in obese vs. lean Zucker rats is accompanied by altered hypothalamic monoaminergic activity, the physiological role of which needs further evaluation; and 2) depressed VMN serotonergic activity is associated with the obese genotype (fa/fa) rather than gender and as such may contribute to the reduced sympathetic and enhanced parasympathetic outflow from the VMN.
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Affiliation(s)
- V H Routh
- Section of Neurobiology, Physiology, and Behavior, Division of Biological Sciences, Univ. of California, Davis, 95616, USA
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Bruder ED, Jacobson L, Raff H. Plasma leptin and ghrelin in the neonatal rat: interaction of dexamethasone and hypoxia. J Endocrinol 2005; 185:477-84. [PMID: 15930174 PMCID: PMC1249478 DOI: 10.1677/joe.1.06159] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Ghrelin, leptin, and endogenous glucocorticoids play a role in appetite regulation, energy balance, and growth. The present study assessed the effects of dexamethasone (DEX) on these hormones, and on ACTH and pituitary proopiomelanocortin (POMC) and corticotropin-releasing hormone receptor-1 (CRHR1) mRNA expression, during a common metabolic stress - neonatal hypoxia. Newborn rats were raised in room air (21% O2) or under normobaric hypoxia (12% O2) from birth to postnatal day (PD) 7. DEX was administered on PD3 (0.5 mg/kg), PD4 (0.25 mg/kg), PD5 (0.125 mg/kg), and PD6 (0.05 mg/kg). Pups were studied on PD7 (24 h after the last dose of DEX). DEX significantly increased plasma leptin and ghrelin in normoxic pups, but only increased ghrelin in hypoxic pups. Hypoxia alone resulted in a small increase in plasma leptin. Plasma corticosterone and pituitary POMC mRNA expression were decreased 24 h following the last dose of DEX, whereas plasma ACTH and pituitary CRHR1 mRNA expression had already increased (normoxia and hypoxia). Hypoxia alone increased corticosterone, but had no effect on ACTH or pituitary POMC and CRHR1 mRNA expression. Neonatal DEX treatment, hypoxia, and the combination of both affect hormones involved in energy homeostasis. Pituitary function in the neonate was quickly restored following DEX-induced suppression of the hypothalamic-pituitary-adrenal axis. The changes in ghrelin, leptin, and corticosterone may be beneficial to the hypoxic neonate through the maintenance of appetite and shifts in intermediary metabolism.
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Affiliation(s)
- Eric D. Bruder
- Endocrine Research Laboratory, St. Luke’s Medical Center, Milwaukee, WI 53215
| | - Lauren Jacobson
- Center for Neuropharmacology and Neurosciences, Albany Medical College, Albany NY 12208
| | - Hershel Raff
- Endocrine Research Laboratory, St. Luke’s Medical Center, Milwaukee, WI 53215
- Department of Medicine, Medical College of Wisconsin, Milwaukee, WI 53226
- Correspondence and Reprint Requests: Hershel Raff, Ph.D., Endocrinology, St. Luke’s Physician’s Office Building, 2801, W. KK River Pky, Suite 245, Milwaukee, WI 53215 USA, Phone: (414) 649-6421, Fax: (414) 649-5747, E-mail:
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Zippel U, Plagemann A, Davidowa H. Altered action of dopamine and cholecystokinin on lateral hypothalamic neurons in rats raised under different feeding conditions. Behav Brain Res 2003; 147:89-94. [PMID: 14659574 DOI: 10.1016/s0166-4328(03)00140-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Single-unit activity was recorded in the lateral hypothalamus (LH) of adult Wistar rats anaesthetized with urethane. The rats were differently nourished till weaning by raising in small (SL), control (CL) or large litters (LL). They gained significantly different body weight leading to overweight in SL (mean: 428.4 g on day 90) and underweight in LL rats (mean 399.5 g) compared to CLs (414.5 g). The mean basal firing rate of LH neurons differed, it was lowest in SL and highest in LL rats. The proportion of neurons changing their firing rate by more than 30% in response to iontophoretically administered dopamine (DA) was significantly greater in SL (76%) than LL rats (54%). Effects of DA were significantly more often blocked by a D1 receptor antagonist in LL than CLs. The responsiveness to cholecystokinin (CCK) alone and coadministered with DA was also greater in SL than LL. Furthermore, the proportion of neurons inhibited by DA alone and in the presence of CCK was significantly greater in SL than LL rats. In conclusion, litter size and difference in nourishment during early postnatal development of rats seem to determine LH basal firing rate. The increased neuronal responsiveness to exogenous DA and CCK in neonatally overfed SL rats may indicate a decreased activity of these endogenous signals which normally contribute to limitation of energy intake.
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Affiliation(s)
- Ursula Zippel
- Johannes Mueller Institute of Physiology, Charité, Humboldt University Berlin, Tucholskystr. 2, D-10117 Berlin, Germany
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Svec F, Thompson H, Corll C, Porter J. Levels of hypothalamic neurotransmitters in lean and obese Zucker rats. Nutr Neurosci 2002; 5:321-6. [PMID: 12385594 DOI: 10.1080/1028415021000033785] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Hypothalamic neurotransmitter levels were compared between groups of Zucker rats. Animals were grouped by gender, phenotype and preference for dietary fat. Before sacrifice all animals consumed a standard rat chow diet and were fasted overnight. Five rats from each of eight groups were assayed. Hypothalamic regions (lateral, LH; ventromedial, VMH; paraventricular, PVN) and the raphe were isolated and analyzed for dopamine, norepinephrine, epinephrine, serotonin and 5-hydroxyindoleacetic acid. A factorial analysis of variance was used to compare the concentrations of these biogenic amines in the four regions across phenotypic, gender and fat preference profiles. No differences were demonstrated between groups based upon fat food preference. Epinephrine and 5-HIAA content varied between lean and obese animals but there were no differences in the content of serotonin, norepinephrine or dopamine. The results are consistent with the hypothesis that the obese animal eats more because it releases less of the satiety-inducing neurotransmitter serotonin in the hypothalamus.
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Affiliation(s)
- Frank Svec
- Obesity Research Program Department of Medicine, Louisiana State University Health Sciences Center, New Orleans 70112, USA.
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Davidowa H, Heidel E, Plagemann A. Differential involvement of dopamine D1 and D2 receptors and inhibition by dopamine of hypothalamic VMN neurons in early postnatally overfed juvenile rats. Nutr Neurosci 2002; 5:27-36. [PMID: 11929195 DOI: 10.1080/10284150290007056] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Dopamine is among the neurotransmitters involved in central regulation of food intake, and body weight control. To study possible changes in neuronal responses to dopamine, single unit activity of the ventromedial hypothalamic nucleus (VMN) was recorded in brain slices of normal and obese rats. The latter had developed overweight throughout juvenile life (p < 0.05) by early postnatal over-nourishment due to a reduction of litter size from 3rd to 21st day of life (small litters, SL). With effective concentrations of about 100-500 nM/I dopamine inhibited significantly more VMN neurons in obese than normal rats (Chi-square p < 0.05). While D2 receptors in the VMN are reported to mediate inhibition of food intake, the responses to dopamine were blocked by D2 receptor antagonists in significantly fewer neurons of SL than normal rats (p < 0.05). Furthemore, including results of action of D1 receptor agonists we found that significantly more neurons in SL than NL rats seem to express D1 receptors. Thus, increased suppression by dopamine of firing of VMN neurons that signal satiety with a rise in the discharge rate, and changed expression or activity of dopamine receptors might contribute to increased feeding behavior in juvenile rats hyperphagic and overweight due to early postnatal overfeeding.
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Affiliation(s)
- Helga Davidowa
- Johannes-Mueller-Institute of Physiology, Faculty of Medicine, Charité, Humboldt University Berlin, Germany.
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De Fanti BA, Gavel DA, Hamilton JS, Horwitz BA. Extracellular hypothalamic serotonin levels after dorsal raphe nuclei stimulation of lean (Fa/Fa) and obese (fa/fa) Zucker rats. Brain Res 2000; 869:6-14. [PMID: 10865053 DOI: 10.1016/s0006-8993(00)02308-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Serotonin (5-HT), acting in the medial hypothalamus (MH), is involved in appetite/satiety and sympathetic stimulation of thermogenesis. This study tested the hypothesis that the enhanced energetic efficiency of obese Zucker rats is associated with a reduced capacity of activated dorsal raphe (DR) neurons to release 5-HT in the MH. We used microdialysis and HPLC-EC to measure dynamic changes in extracellular 5-HT levels in the MH of urethane-anesthetized, 10-14 week old male lean and obese Zucker rats. These concentrations did not differ significantly between the two genotypes prior to stimulation (mean+/-S.E.M.=3.8+/-0.5 fmol/microl, lean; 3.6+/-1.0 fmol/microl, obese) or following DR stimulation at 25 Hz (200 microA). The latter elicited initial net increases of 0.54+/-0.15 fmol/microl in lean and 0.58+/-0.20 fmol/microl in obese rats; and 20 min post-stimulus, 5-HT values were still elevated and comparable in the two genotypes. Although a 50-Hz (200 microA) stimulus evoked initial increases that were similar in lean (1.37+/-0.23 fmol/microl) and obese (0.95+/-0.24 fmol/microl,) rats, the net increase in 5-HT concentration during the next 20-40 min period was higher in the lean (2.03+/-0.55 fmol/microl vs. 1.18+/-0.24 fmol/microl in the obese animals). Also, in the lean, but not obese rats, extracellular 5-HT levels were significantly greater at 50 vs. 25 Hz. These results support the hypothesis that the capacity of midbrain serotonergic neurons to release 5-HT at the MH is reduced in obese Zucker rats, consistent with their blunted responsiveness to dietary stimuli and greater energetic efficiency.
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Affiliation(s)
- B A De Fanti
- University of California, Division of Biological Sciences, Neurobiology, Physiology and Behavior, One Shields Avenue, Davis, CA 95616-8519, USA
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Horwitz BA, Hamilton JS, Routh VH, Green K, Havel P, Chan A. Adiposity and serum leptin increase in fatty (fa/fa) BNZ neonates without decreased VMH serotonergic activity. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 274:E1009-17. [PMID: 9611150 DOI: 10.1152/ajpendo.1998.274.6.e1009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Decreased ventromedial hypothalamic (VMH) serotonergic activity occurs in genetic and diet-induced animal models of obesity. We previously found that this activity was lower in adult and in 12-day-old Zucker fa/fa vs. Fa/Fa pups, the fa/fa animals being identified by their greater adiposity. In the present study, we evaluated fa/fa rats (Brown Norway-Zucker hybrids) at ages 2, 4, 7, and 12 days to test the hypothesis that lower VMH serotonergic activity occurs before increased adiposity and/or attenuated energy expenditure. Our results negate this hypothesis. VMH serotonergic activity showed no consistent genotype differences even at 12 days of age. In contrast, by day 7, fa/fa vs. Fa/Fa pups had higher serum leptin concentrations, greater percent body fat, lower resting and cold-induced energy expenditure, and lower activity of brown fat thyroxine 5'-deiodinase, an enzyme that converts thyroxine to triiodothyronine. We conclude that the onset of increased adiposity induced by the fa gene does not require decreased VMH serotonergic activity and that the lower serotonergic activity seen in older fa/fa pups may be secondary to metabolic consequences of the disruption of the leptin regulatory pathway.
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Affiliation(s)
- B A Horwitz
- Section of Neurobiology, Physiology, and Behavior, University of California, Davis, California 95616, USA
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Routh VH, Stern JS, Horwitz BA. Physiological Responses of Mammals to Overnutrition. Compr Physiol 1996. [DOI: 10.1002/cphy.cp040262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Routh VH, Stern JS, Horwitz BA. Adrenalectomy increases serotonin turnover in brains of obese Zucker rats. Physiol Behav 1995; 58:491-9. [PMID: 8587957 DOI: 10.1016/0031-9384(95)00079-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Because adrenalectomy tends to normalize many metabolic abnormalities of obese Zucker rats, we hypothesized that it would also normalize the depressed serotonergic turnover in their ventromedial nucleus (VMN). Lean (Fa/Fa) and obese (fa/fa) male Zucker rats were adrenalectomized or sham operated when 5 wks old and sacrificed at 11 wks. Their brains were frozen, and 13 areas were dissected for HPLC-EC analysis of monoamines and metabolites. Consistent with previous studies, VMN serotonin turnover (indexed by 5-HIAA/5-HT) was lower in obese than lean sham-operated rats. Monoamine and metabolite concentrations were altered in several other brain areas as well. Adrenalectomy reduced percent body fat and elevated VMN serotonergic turnover more in obese than in lean rats. It also stimulated serotonergic turnover in almost every brain area examined. We conclude that in obese Zucker rats: monoaminergic activity is altered in several brain areas involved in regulating energy balance; adrenalectomy normalizes the reduced VMN serotonergic turnover seen in the obese rats; and adrenalectomy results in a generalized increase in central serotonergic turnover. These data are consistent with serotonin's role in inhibiting food intake and enhancing sympathetic stimulation of energy metabolism.
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Affiliation(s)
- V H Routh
- Department of Nutrition, University of California at Davis 95616, USA
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