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Mohammad S, Ozaki T, Takeuchi K, Unno K, Yamoto K, Morioka E, Takiguchi S, Ikeda M. Functional compensation between cholecystokinin-1 and -2 receptors in murine paraventricular nucleus neurons. J Biol Chem 2012; 287:39391-401. [PMID: 23038256 PMCID: PMC3501058 DOI: 10.1074/jbc.m112.416214] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Revised: 10/02/2012] [Indexed: 01/11/2023] Open
Abstract
Cholecystokinin (CCK) and its receptor subtypes CCK-1 and -2 have diverse homeostatic functions. CCK-1 and -2 receptors share a common phosphatidylinositol signaling pathway, yet little is known regarding their possible functional coupling. We focused on CCK-mediated Ca(2+) signaling in parvocellular paraventricular nucleus (PVN) cells, which control satiety and other autonomic functions. Analysis of mouse hypothalamic slices demonstrated that the general CCK receptor agonist CCK-8s (10 nM) triggered Ca(2+) transients most significantly in the posterior subregion of the PVN (PaPo). This 10 nM CCK-8s-induced response was absent in CCK-1 receptor knock-out (CCK1R(-/-)) slices, showing that the response is mediated by CCK-1 receptors. CCK-8s concentrations higher than 30 nM triggered a Ca(2+) rise similarly in wild-type and CCK1R(-/-) slices. The large CCK-8s (100 nM)-induced Ca(2+) responses in CCK1R(-/-) slices were blocked by a CCK-2 receptor antagonist (CI-988), whereas those in wild-type slices required a mixture of CI-988 and lorglumide (a CCK-1 receptor antagonist) for complete antagonism. Therefore, CCK-1 and -2 receptors may function synergistically in single PaPo neurons and deletion of CCK-1 receptors may facilitate CCK-2 receptor signaling. This hypothesis was supported by results of real-time RT-PCR, immunofluorescence double labeling and Western blotting assays, which indicated CCK-2 receptor overexpression in PaPo neurons of CCK1R(-/-) mice. Furthermore, behavioral studies showed that intraperitoneal injections of lorglumide up-regulated food accesses in wild-type but not in CCK1R(-/-) mice, whereas CI-988 injections up-regulated food accesses in CCK1R(-/-) but not in wild-type mice. Compensatory CCK signaling via CCK-2 receptors in CCK1R(-/-) mice shed light on currently controversial satiety-controlling mechanisms.
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Affiliation(s)
| | - Tomoya Ozaki
- From the Graduate School of Innovative Life Science and
| | - Kouhei Takeuchi
- the Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama-city, Toyama 930-8555 and
| | - Katsuya Unno
- the Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama-city, Toyama 930-8555 and
| | - Kurumi Yamoto
- the Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama-city, Toyama 930-8555 and
| | - Eri Morioka
- From the Graduate School of Innovative Life Science and
| | - Soichi Takiguchi
- the Institute for Clinical Research, National Kyushu Cancer Center, 3-1-1 Notame, Minami-ku, Fukuoka 811-1395, Japan
| | - Masayuki Ikeda
- From the Graduate School of Innovative Life Science and
- the Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama-city, Toyama 930-8555 and
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Schneider JE, Klingerman CM, Abdulhay A. Sense and nonsense in metabolic control of reproduction. Front Endocrinol (Lausanne) 2012; 3:26. [PMID: 22649413 PMCID: PMC3355988 DOI: 10.3389/fendo.2012.00026] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/06/2011] [Accepted: 02/04/2012] [Indexed: 12/16/2022] Open
Abstract
An exciting synergistic interaction occurs among researchers working at the interface of reproductive biology and energy homeostasis. Reproductive biologists benefit from the theories, experimental designs, and methodologies used by experts on energy homeostasis while they bring context and meaning to the study of energy homeostasis. There is a growing recognition that identification of candidate genes for obesity is little more than meaningless reductionism unless those genes and their expression are placed in a developmental, environmental, and evolutionary context. Reproductive biology provides this context because metabolic energy is the most important factor that controls reproductive success and gonadal hormones affect energy intake, storage, and expenditure. Reproductive hormone secretion changes during development, and reproductive success is key to evolutionary adaptation, the process that most likely molded the mechanisms that control energy balance. It is likely that by viewing energy intake, storage, and expenditure in the context of reproductive success, we will gain insight into human obesity, eating disorders, diabetes, and other pathologies related to fuel homeostasis. This review emphasizes the metabolic hypothesis: a sensory system monitors the availability of oxidizable metabolic fuels and orchestrates behavioral motivation to optimize reproductive success in environments where energy availability fluctuates or is unpredictable.
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Affiliation(s)
- Jill E Schneider
- Department of Biological Sciences, Lehigh University Bethlehem, PA, USA.
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Klingerman CM, Williams WP, Simberlund J, Brahme N, Prasad A, Schneider JE, Kriegsfeld LJ. Food Restriction-Induced Changes in Gonadotropin-Inhibiting Hormone Cells are Associated with Changes in Sexual Motivation and Food Hoarding, but not Sexual Performance and Food Intake. Front Endocrinol (Lausanne) 2011; 2:101. [PMID: 22649396 PMCID: PMC3355909 DOI: 10.3389/fendo.2011.00101] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/03/2011] [Accepted: 12/01/2011] [Indexed: 12/20/2022] Open
Abstract
We hypothesized that putative anorectic and orexigenic peptides control the motivation to engage in either ingestive or sex behaviors, and these peptides function to optimize reproductive success in environments where energy fluctuates. Here, the putative orexigenic peptide, gonadotropin-inhibiting hormone (GnIH, also known as RFamide-related peptide-3), and the putative anorectic hormones leptin, insulin, and estradiol were examined during the course of food restriction. Groups of female Syrian hamsters were restricted to 75% of their ad libitum food intake or fed ad libitum for 4, 8, or 12 days. Two other groups were food-restricted for 12 days and then re-fed ad libitum for 4 or 8 days. After testing for sex and ingestive behavior, blood was sampled and assayed for peripheral hormones. Brains were immunohistochemically double-labeled for GnIH and the protein product of the immediate early gene, c-fos, a marker of cellular activation. Food hoarding, the number of double-labeled cells, and the percent of GnIH-Ir cells labeled with Fos-Ir were significantly increased at 8 and 12 days after the start of food restriction. Vaginal scent marking and GnIH-Ir cell number significantly decreased after the same duration of restriction. Food hoarding, but not food intake, was significantly positively correlated with cellular activation in GnIH-Ir cells. Vaginal scent marking was significantly negatively correlated with cellular activation in GnIH-Ir cells. There were no significant effects of food restriction on plasma insulin, leptin, estradiol, or progesterone concentrations. In the dorsomedial hypothalamus (DMH) of energetically challenged females, strong projections from NPY-Ir cells were found in close apposition to GnIH-Ir cells. Together these results are consistent with the idea that metabolic signals influence sexual and ingestive motivation via NPY fibers that project to GnIH cells in the DMH.
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Affiliation(s)
| | - Wilbur P. Williams
- Department of Psychology, Helen Wills Neuroscience Institute, University of CaliforniaBerkeley, CA, USA
| | | | - Nina Brahme
- Department of Psychology, Helen Wills Neuroscience Institute, University of CaliforniaBerkeley, CA, USA
| | - Ankita Prasad
- Department of Psychology, Helen Wills Neuroscience Institute, University of CaliforniaBerkeley, CA, USA
| | - Jill E. Schneider
- Department of Biological Sciences, Lehigh UniversityBethlehem, PA, USA
- *Correspondence: Jill E. Schneider, Department of Biological Sciences, Lehigh University,111 Research Drive, Bethlehem, PA 18015, USA. e-mail:
| | - Lance J. Kriegsfeld
- Department of Psychology, Helen Wills Neuroscience Institute, University of CaliforniaBerkeley, CA, USA
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Hobbs NJ, Aven AM, Ferkin MH. Self-Grooming Response of Meadow Voles to the Odor of Opposite-Sex Conspecifics in Relation to the Dietary Protein Content of Both Sexes. Ethology 2008. [DOI: 10.1111/j.1439-0310.2008.01573.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Abstract
PURPOSE OF REVIEW To summarize the physiological bases of infertility during undernutrition. RECENT FINDINGS When energy expenditure consistently exceeds intake, survival receives temporary priority over fertility, and reproduction is deferred until conditions are more favorable. This nutritional infertility is due to inhibition of both gonadotropin-releasing hormone secretion and copulatory behaviors. Recent work has focused on the nature of the metabolic signals to the brain, detection of these signals, and the neural circuitry involved. This work is reviewed and summarized. SUMMARY It was once erroneously believed that female mammals had to maintain a particular body fat content to remain fertile. We now know that the primary metabolic factor is short-term availability of glucose and fatty acids for oxidation. Metabolic fuel availability is detected in the caudal hindbrain and possibly elsewhere. This information is relayed to the forebrain via projections containing catecholamines and neuropeptide-Y, where they activate corticotropin-releasing hormone neurons. Acting as a neurotransmitter, this hormone inhibits gonadotropin-releasing hormone secretion and estrous behavior. Conversely, corticotropin-releasing hormone antagonists reverse the effects of food deprivation on both measures, indicating that corticotropin-releasing hormone is vital in the nutritional suppression of reproduction. Leptin may modulate reproductive responses to changes in short-term fuel availability.
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Affiliation(s)
- Maria Furman
- Division of Endocrinology, Diabetes, and Hypertension, Brigham and Women's Hospital, Boston, Massachusetts, USA
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Pierce AA, Iwueke I, Ferkin MH. Food deprivation and the role of estradiol in mediating sexual behaviors in meadow voles. Physiol Behav 2006; 90:353-61. [PMID: 17112551 PMCID: PMC1855151 DOI: 10.1016/j.physbeh.2006.09.034] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2005] [Revised: 09/11/2006] [Accepted: 09/22/2006] [Indexed: 11/21/2022]
Abstract
Female mammals are particularly sensitive to changes in food availability. The mechanisms that affect sexual behavior and food intake are closely related to one another; chief among the mechanisms that control sexual behaviors in females is estradiol. In order to understand how food deprivation results in inhibition of sexual behavior (attractivity, proceptivity, and receptivity), we measured the effects of food deprivation on circulating concentrations of estradiol. We also determined whether estradiol treatment was sufficient to restore sexual behaviors in food-deprived female meadow voles. We found that estradiol titers of food-deprived female voles are significantly lower than those of ad lib-fed female voles. Further, we found that estradiol treatment was sufficient to restore proceptivity and receptivity in food-deprived, ovariectomized female voles. However, estradiol treatment was not able to overcome the food deprivation-induced inhibition of attractivity. Thus, decreases in estradiol titer of food-deprived female voles may be related to the suppression of their proceptive and receptive behaviors, and may be a mechanism that allows females to avoid mating when conditions are not propitious for their survival and that of their offspring.
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Affiliation(s)
- Andrew A Pierce
- University of Memphis, Department of Biology, Memphis, TN 38152, United States.
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Seymour PL, Dettloff SL, Jones JE, Wade GN. Corticotropin-releasing factor receptor subtypes mediating nutritional suppression of estrous behavior in Syrian hamsters. Am J Physiol Regul Integr Comp Physiol 2005; 289:R418-R423. [PMID: 15831766 DOI: 10.1152/ajpregu.00168.2005] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Caloric deprivation inhibits reproduction, including copulatory behaviors, in female mammals. Decreases in metabolic fuel availability are detected in the hindbrain, and this information is relayed to the forebrain circuits controlling estrous behavior by neuropeptide Y (NPY) projections. In the forebrain, the nutritional inhibition of estrous behavior appears to be mediated by corticotropin-releasing factor (CRF) or urocortin-signaling systems. Intracerebroventricular (ICV) infusion of the CRF antagonist, astressin, prevents the suppression of lordosis by food deprivation and by NPY treatment in Syrian hamsters. These experiments sought to determine which CRF receptor type(s) is involved. ICV infusion of the CRF receptor subtype CRFR2-selective agonists urocortin 2 and 3 (UCN2, UCN3) inhibited sexual receptivity in hormone-primed, ovariectomized hamsters. Furthermore, the CRFR2-selective antagonist, astressin 2B, prevented the inhibition of estrous behavior by UCN2 and by NPY, consistent with a role for CRFR2. On the other hand, astressin 2B did not prevent the inhibition of behavior induced by 48-h food deprivation or ICV administration of CRF, a mixed CRFR1 and CRFR2 agonist, suggesting that activation of CRFR1 signaling is sufficient to inhibit sexual receptivity in hamsters. Although administration of CRFR1-selective antagonists (NBI-27914 and CP-154,526) failed to reverse the inhibition of receptivity by CRF treatment, we could not confirm their biological effectiveness in hamsters. The most parsimonious interpretation of these findings is that, although NPY inhibits estrous behavior via downstream CRFR2 signaling, food deprivation may exert its inhibition via both CRFR1 and CRFR2 and that redundant neuropeptide systems may be involved.
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Affiliation(s)
- Patricia L Seymour
- Center for Neuroendocrine Studies, University of Massachusetts, 135 Hicks Way, Amherst, MA 01003, USA
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Wade GN, Jones JE. Neuroendocrinology of nutritional infertility. Am J Physiol Regul Integr Comp Physiol 2005; 287:R1277-96. [PMID: 15528398 DOI: 10.1152/ajpregu.00475.2004] [Citation(s) in RCA: 164] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Natural selection has linked the physiological controls of energy balance and fertility such that reproduction is deferred during lean times, particularly in female mammals. In this way, an energetically costly process is confined to periods when sufficient food is available to support pregnancy and lactation. Even in the face of abundance, nutritional infertility ensues if energy intake fails to keep pace with expenditure. A working hypothesis is proposed in which any activity or condition that limits the availability of oxidizable fuels (e.g., undereating, excessive energy expenditure, diabetes mellitus) can inhibit both gonadotropin-releasing hormone (GnRH)/luteinizing hormone secretion and female copulatory behaviors. Decreases in metabolic fuel availability appear to be detected by cells in the caudal hindbrain. Hindbrain neurons producing neuropeptide Y (NPY) and catecholamines (CA) then project to the forebrain where they contact GnRH neurons both directly and also indirectly via corticotropin-releasing hormone (CRH) neurons to inhibit GnRH secretion. In the case of estrous behavior, the best available evidence suggests that the inhibitory NPY/CA system acts primarily via CRH or urocortin projections to various forebrain loci that control sexual receptivity. Disruption of these signaling processes allows normal reproduction to proceed in the face of energetic deficits, indicating that the circuitry responds to energy deficits and that no signal is necessary to indicate that there is an adequate energy supply. While there is a large body of evidence to support this hypothesis, the data do not exclude nutritional inhibition of reproduction by other pathways and processes, and the full story will undoubtedly be more complex than this.
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Affiliation(s)
- George N Wade
- Center for Neuroendocrine Studies, University of Massachusetts, 135 Hicks Way, Amherst, MA 01003, USA.
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Abstract
In female mammals reproduction is highly sensitive to the food supply. During lean times, females suspend reproductive attempts in favor of maintaining processes necessary for survival; fertility is restored once the food supply is again abundant. Nearly all aspects of reproduction are affected, including puberty, adult ovulatory cycles, and reproductive behaviors. Work with experimental animals reveals that caloric restriction inhibits release of luteinizing hormone (LH) and female sexual behavior via similar, although separate, processes. The primary metabolic event affecting LH release as well as female sexual behavior is the short-term (minute-to-minute, hour-to-hour) availability of oxidizable metabolic fuels, rather than any aspect of body size or composition (e.g., body fat content). Metabolic fuel availability is detected in the hindbrain and perhaps in peripheral tissues. Metabolic information is then transmitted synaptically from the visceral hindbrain to the forebrain effector circuits. In the forebrain, signaling via corticotropin-releasing hormone receptors appears to be crucial for inhibition of both LH secretion and female sexual behavior.
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Affiliation(s)
- George N Wade
- Center for Neuroendocrine Studies, University of Massachusetts, Amherst, MA 01003, USA.
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Keene AC, Jones JE, Wade GN, Corp ES. Forebrain sites of NPY action on estrous behavior in Syrian hamsters. Physiol Behav 2003; 78:711-6. [PMID: 12782227 DOI: 10.1016/s0031-9384(03)00048-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Food deprivation and similar metabolic challenges inhibit estrous behavior in female Syrian hamsters. The relevant metabolic cues appear to be detected in the hindbrain, and this information is then relayed synaptically to the forebrain circuits controlling estrous behavior. Neuropeptide Y (NPY) may be one of the neuropeptides/neurotransmitters serving this function. Infusion of NPY or the Y2/Y5 agonist, peptide YY3-36 (PYY3-36), into the lateral ventricles rapidly inhibits estrous behavior in ovariectomized, steroid-primed hamsters. This experiment sought to determine the neural loci where NPY acts to inhibit estrous behavior. Steroid-primed animals received infusions of artificial cerebrospinal fluid (aCSF) vehicle, 0.024 nmol PYY3-36 and 0.24 nmol PYY3-36 in separate tests 30 min prior to testing for sexual receptivity. Infusion of 0.24 nmol, but not 0.024 nmol, of PYY3-36 reduced lordosis duration when infused into the paraventricular nucleus of the hypothalamus (PVN), the caudal part of the medial preoptic area (MPO), the anterior hypothalamus (AH) or the lateral ventricles. Placements in the ventromedial hypothalamus (VMH), the arcuate nucleus (ARC) and the fourth ventricle were generally without effect. These data suggest that increased endogenous release of NPY into the caudal MPO-AH-PVN continuum during food deprivation could contribute to the observed inhibition of sexual receptivity. The possible contributions of other neuropeptides and neural estrogen receptors to this action of NPY are discussed.
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Affiliation(s)
- Alex C Keene
- Center for Neuroendocrine Studies, University of Massachusetts, 135 Hicks Way, Amherst, MA 01003, USA
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Jones JE, Pick RR, Davenport MD, Keene AC, Corp ES, Wade GN. Disinhibition of female sexual behavior by a CRH receptor antagonist in Syrian hamsters. Am J Physiol Regul Integr Comp Physiol 2002; 283:R591-7. [PMID: 12184992 DOI: 10.1152/ajpregu.00233.2002] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Several conditions that inhibit female sexual behavior are thought to be associated with altered corticotropin-releasing hormone (CRH) activity in the brain. The present experiments examined the hypothesis that endogenous CRH receptor signaling mediates the inhibition of estrous behavior by undernutrition and in other instances of sexual dysfunction. Intracerebroventricular (ICV) infusion of CRH or urocortin inhibited estrous behavior in ovariectomized steroid-primed hamsters. Conversely, ICV infusion of the CRH receptor antagonist astressin prevented the suppression of estrous behavior by food deprivation or by ICV administration of neuropeptide Y. Astressin treatment also induced sexual receptivity in nonresponders, animals that do not normally come into heat when treated with hormones, and this effect persisted in subsequent weekly tests in the absence of any further astressin treatment. Activation of the hypothalamo-pituitary-adrenocortical axis was neither necessary nor sufficient to inhibit estrous behavior, indicating that this phenomenon is due to other central actions of CRH receptor agonists. This is the first direct evidence that CRH receptor signaling may be a final common pathway by which undernutrition and other conditions inhibit female sexual behavior.
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Affiliation(s)
- Juli E Jones
- Center for Neuroendocrine Studies, University of Massachusetts, Amherst, Massachusetts 01003, USA.
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Corp ES, Gréco B, Powers JB, Marín Bivens CL, Wade GN. Neuropeptide Y inhibits estrous behavior and stimulates feeding via separate receptors in Syrian hamsters. Am J Physiol Regul Integr Comp Physiol 2001; 280:R1061-8. [PMID: 11247828 DOI: 10.1152/ajpregu.2001.280.4.r1061] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Central injections of neuropeptide Y (NPY) increase food intake in Syrian hamsters; however, the effect of NPY on sexual behavior in hamsters is not known nor are the receptor subtypes involved in feeding and sexual behaviors. We demonstrate that NPY inhibits lordosis duration in a dose-related fashion after lateral ventricular injection in ovariectomized, steroid-primed Syrian hamsters. Under the same conditions, we compared the effect of two receptor-differentiating agonists derived from peptide YY (PYY), PYY-(3-36) and [Leu(31),Pro(34)]PYY, on lordosis duration and food intake. PYY-(3-36) produced a 91% reduction in lordosis duration at 0.24 nmol. [Leu(31),Pro(34)]PYY was less potent, producing a reduction in lordosis duration (66%) only at 2.4 nmol. These results suggest NPY effects on estrous behavior are principally mediated by Y2 receptors. PYY-(3-36) and [Leu(31),Pro(34)]PYY stimulated comparable dose-related increases in total food intake (2 h), suggesting Y5 receptors are involved in feeding. The significance of different NPY receptor subtypes controlling estrous and feeding behavior is highlighted by results on expression of Fos immunoreactivity (Fos-IR) elicited by either PYY-(3-36) or [Leu(31),Pro(34)]PYY at a dose of each that differentiated between the two behaviors. Some differences were seen in the distribution of Fos-IR produced by the two peptides. Overall, however, the patterns of expression were similar. Our behavioral and anatomic results suggest that NPY-containing pathways controlling estrous and feeding behavior innervate similar nuclei, with the divergence in pathways controlling the separate behaviors characterized by linkage to different NPY receptor subtypes.
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Affiliation(s)
- E S Corp
- Center for Neuroendocrine Studies, Neuroscience and Behavior Program and Department of Psychology,, Box 37720, University of Massachusetts-Amherst, Amherst, MA 01003, USA.
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Bae HH, Stamper JL, Heydorn EC, Zucker I, Dark J. Role of area postrema in control of torpor in Siberian hamsters. Am J Physiol Regul Integr Comp Physiol 2000; 279:R591-8. [PMID: 10938250 DOI: 10.1152/ajpregu.2000.279.2.r591] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Siberian hamsters undergo torpor during the short days of winter and in response to glucoprivation or food restriction. We tested whether the area postrema and the adjacent nucleus of the solitary tract (hereafter the AP), which monitor metabolic fuel availability, also control the onset of torpor. Siberian hamsters that had manifested torpor spontaneously or had entered torpor in response to 2-deoxy-D-glucose (2-DG) treatment were subjected to area postrema ablations (APx). Hamsters continued to display torpor postoperatively; most features of torpor were unaffected by APx. The AP is not necessary for expression of torpor elicited by short day lengths or metabolic challenge. In contrast, decreases in food intake manifested by hamsters treated with 2-DG were counteracted by APx. In Siberian hamsters, the AP appears to mediate effects of 2-DG on food intake but not torpor.
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Affiliation(s)
- H H Bae
- Group in Endocrinology, University of California, Berkeley 94720, USA.
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