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Selected hormonal and neurotransmitter mechanisms regulating feed intake in sheep

Published online by Cambridge University Press:  22 July 2010

J. L. Sartin ,
J. A. Daniel ,
B. K. Whitlock  and
R. R. Wilborn
J. L. Sartin*
Affiliation:
Department of Anatomy, Physiology & Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, USA
J. A. Daniel
Affiliation:
Department of Animal Science, Berry College, Mt. Berry, GA 30149, USA
B. K. Whitlock
Affiliation:
Department of Large Animal Clinical Sciences, College of Veterinary Medicine, The University of Tennessee, Knoxville, TN 37996, USA
R. R. Wilborn
Affiliation:
Department of Clinical Sciences, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, USA
*
†E-mail: [email protected]
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Abstract

Appetite control is a major issue in normal growth and in suboptimal growth performance settings. A number of hormones, in particular leptin, activate or inhibit orexigenic or anorexigenic neurotransmitters within the arcuate nucleus of the hypothalamus, where feed intake regulation is integrated. Examples of appetite regulatory neurotransmitters are the stimulatory neurotransmitters neuropeptide Y (NPY), agouti-related protein (AgRP), orexin and melanin-concentrating hormone and the inhibitory neurotransmitter, melanocyte-stimulating hormone (MSH). Examination of messenger RNA (using in situ hybridization and real-time PCR) and proteins (using immunohistochemistry) for these neurotransmitters in ruminants has indicated that physiological regulation occurs in response to fasting for several of these critical genes and proteins, especially AgRP and NPY. Moreover, intracerebroventricular injection of each of the four stimulatory neurotransmitters can increase feed intake in sheep and may also regulate either growth hormone, luteinizing hormone, cortisol or other hormones. In contrast, both leptin and MSH are inhibitory to feed intake in ruminants. Interestingly, the natural melanocortin-4 receptor (MC4R) antagonist, AgRP, as well as NPY can prevent the inhibition of feed intake after injection of endotoxin (to model disease suppression of appetite). Thus, knowledge of the mechanisms regulating feed intake in the hypothalamus may lead to mechanisms to increase feed intake in normal growing animals and prevent the wasting effects of severe disease in animals.

Keywords

appetiteneuropeptide Yproopiomelanocortinleptinsheep
Type
EAAP-ASAS-ADSA Growth and Development Symposium 2008
Information
animal , Volume 4 , Issue 11 , November 2010 , pp. 1781 - 1789
Copyright
Copyright © The Animal Consortium 2010

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References

Adam, CL, Findlay, PA, Miller, DW 2006. Blood-brain leptin transport and appetite and reproductive neuroendocrine responses to intracerebroventricular leptin injection in sheep: influence of photoperiod. Endocrinology 147, 4589–4598.CrossRefGoogle ScholarPubMed
Adam, CL, Archer, ZA, Findlay, PA, Thomas, L, Marie, M 2002. Hypothalamic gene expression in sheep for cocaine-and amphetamine-regulated transcript, pro-opiomelanocortin, neuropeptide Y, agouti-related peptide and leptin receptor and responses to negative energy balance. Neuroendocrinology 75, 250–256.CrossRefGoogle ScholarPubMed
Altmann, M, Sauerwein, H, Borell, E 2005. Relationship between plasma leptin concentrations and carcass composition in fattening mutton: a comparison with ultrasound results. Journal of Animal Physiology and Animal Nutrition (Berlin) 89, 326–330.CrossRefGoogle Scholar
Anukulkitch, C, Rao, A, Dunchea, FR, Clarke, IJ 2009. A test of the lipostat theory in a seasonal (ovine) model under natural conditions reveals a close relationship between adiposity and melanin concentrating hormone expression. Domestic Animal Endocrinology 36, 138–151.CrossRefGoogle Scholar
Anukulkitch, C, Rao, A, Periera, A, McEwan, J, Clarke, IJ 2010. Expression of genes for appetite-regulating peptides in the hypothalamus of genetically selected lean and fat sheep. Neuroendocrinology 91, 223–238. (doi: 10.1159/000262283).CrossRefGoogle ScholarPubMed
Archer, ZA, Rhind, SM, Findlay, PA, Kyle, CE, Thomas, L, Marie, M, Adam, CL 2002a. Contrasting effects of different levels of food intake and adiposity on LH secretion and hypothalamic gene expression in sheep. Journal of Endocrinology 175, 383–393.CrossRefGoogle ScholarPubMed
Archer, ZA, Findlay, PA, Rhind, SM, Mercer, JG, Adam, CL 2002b. Orexin gene expression and regulation by photoperiod in the sheep hypothalamus. Regulatory Peptides 104, 41–45.CrossRefGoogle ScholarPubMed
Archer, ZA, Findlay, PA, McMillen, SR, Rhind, SM, Adam, CL 2004. Effects of nutritional status and gonadal steroids on expression of appetite-regulatory genes in the hypothalamic arcuate nucleus of sheep. Journal of Endocrinology 182, 409–419.CrossRefGoogle ScholarPubMed
Archer, ZA, Rhind, SM, Findlay, PA, Kyle, CE, Barber, MC, Adam, CL 2005. Hypothalamic responses to peripheral glucose infusion in food-restricted sheep are influenced by photoperiod. Journal of Endocrinology 184, 515–525.CrossRefGoogle ScholarPubMed
Backholer, K, Smith, J, Clarke, IJ 2009. Melanocortins may stimulate reproduction by activating orexin neurons in the dorsomedial hypothalamus and kisspeptin neurons in the preoptic area of the ewe. Endocrinology 150, 5488–5497.CrossRefGoogle ScholarPubMed
Chaillou, E, Tillet, Y 2005. Nutrition and hypothalamic neuropeptides in sheep: histochemical studies. Histology and Histopathology 20, 1209–1225.Google ScholarPubMed
Chaillou, E, Baumont, R, Tramu, G, Tillet, Y 2000. Effect of feeding on Fos protein expression in sheep hypothalamus with special reference to the supraoptic and paraventricular nuclei: an immunohistochemical study. European Journal of Neuroscience 12, 4515–4524.CrossRefGoogle Scholar
Chaillou, E, Baumont, R, Chilliard, Y, Tillet, Y 2002. Several subpopulations of neuropeptide Y-containing neurons exist in the infundibular nucleus of sheep: an immunohistochemical study of animals on different diets. Journal of Comparative Neurology 444, 129–143.CrossRefGoogle ScholarPubMed
Chaillou, E, Baumont, R, Fellman, D, Tramu, G, Tillet, Y 2003. Sensitivity of galanin- and melanin concentrating hormone-containing neurons to nutritional status: an immunohistochemical study in the ovariectomized ewe. Journal of Neuroendocrinology 15, 459–467.CrossRefGoogle ScholarPubMed
Chilliard, Y, Delavaud, C, Bonnet, M 2005. Leptin expression in ruminants: nutritional and physiological regulation in relation with energy metabolism. Domestic Animal Endocrinology 29, 3–22.CrossRefGoogle ScholarPubMed
Clarke, IJ 2008. Models of ‘obesity’ in large animals and birds. Frontiers of Hormone Research (Karger, Basel) 36, 107–117.CrossRefGoogle ScholarPubMed
Clarke, IJ, Backholer, K, Tilbrook, AJ 2005. Y2 receptor-selective agonist delays the estrogen-induced luteinizing hormone surge in ovariectomized ewes, but Y1-receptor-selective agonist stimulates voluntary food intake. Endocrinology 146, 769–775.CrossRefGoogle ScholarPubMed
Clarke, IJ, Scott, CJ, Rao, A, Pompolo, S, Baker-Gibb, ML 2000. Seasonal changes in the expression of neuropeptide Y and pro-opiomelanocortin mRNA in the arcuate nucleus of the ovariectomized ewe: relationship to the seasonal appetite and breeding cycles. Journal of Neuroendocrinology 12, 1105–1111.CrossRefGoogle Scholar
Clarke, IJ, Tilbrook, AJ, Turner, AI, Doughton, BW, Goding, JW 2001. Sex, fat and the tilt of the earth: effects of sex and season on the feeding response to centrally administered leptin in sheep. Endocrinology 142, 2725–2728.CrossRefGoogle ScholarPubMed
Clarke, IJ, Rao, A, Chilliard, Y, Delavaud, C, Lincoln, GA 2003. Photoperiod effects on gene expression for hypothalamic appetite-regulating peptides and food intake in the ram. American Journal of Physiology – Regulatory, Integrative and Comparative Physiology 284, R101–R115.CrossRefGoogle ScholarPubMed
Daniel, JA, Whitlock, BK, Baker, JA, Steele, BP, Morrison, CD, Keisler, DH, Sartin, JL 2002. Effect of body fat mass and nutritional status n 24-hour leptin profiles in ewes. Journal of Animal Science 80, 1083–1089.CrossRefGoogle Scholar
Daniel, JA, Elsasser, TH, Morrison, CD, Keisler, DH, Whitlock, BK, Steele, BP, Pugh, D, Sartin, JL 2003. Leptin, tumor necrosis factor-alpha (TNF), and CD14 in ovine adipose tissue and changes in circulating TNF in lean and fat sheep. Journal of Animal Science 81, 2590–2599.CrossRefGoogle ScholarPubMed
Delavaud, C, Bocquier, F, Baumont, R, Chaillou, E, Ban-Tokuda, T, Chilliard, Y 2007. Body fat content and feeding level interact strongly in the short- and medium-term regulation of plasma leptin during underfeeding and re-feeding in adult sheep. British Journal of Nutrition 98, 106–115.CrossRefGoogle Scholar
Dobbins, A, Lubbers, LS, Jackson, GL, Kuehl, DE, Hileman, SM 2004. Neuropeptide Y gene expression in male sheep: influence of photoperiod and testosterone. Neuroendocrinology 79, 82–89.CrossRefGoogle ScholarPubMed
Dyer, CJ, Simmons, JM, Matteri, RL, Keisler, DH 1997. cDNA cloning and tissue- specific gene expression of ovine leptin, NPY-Y1 receptor, and NPY-Y2 receptor. Domestic Animal Endocrinology 14, 295–303.CrossRefGoogle ScholarPubMed
Ehrhardt, RA, Greenwood, PL, Bell, AW, Boisclair, YR 2003. Plasma leptin is regulated predominantly by nutrition in preruminant lambs. Journal of Nutrition 133, 4196–4201.CrossRefGoogle ScholarPubMed
El-Haddad, MA, Ismail, Y, Guerra, C, Day, L, Ross, MG 2003. Neuropeptide Y administration into cerebral ventricles stimulates sucrose ingestion in the near-trem ovine fetus. American Journal of Obstetrics and Gynecology 189, 949–952.CrossRefGoogle ScholarPubMed
Ellacott, KL, Cone, RD 2004. The central melanocortin system and the integration of short- and long-term regulators of energy homeostasis. Recent Progress in Hormone Research 59, 395–408.CrossRefGoogle Scholar
Greer, AW, Boisclair, YR, Stankiewicz, M, McAnulty, RW, Jay, NP, Sykes, AR 2009. Leptin concentrations and the immune-mediated reduction of feed intake in sheep infected with nematode Trichostrongylus colubriformis. British Journal of Nutrition 102, 954–957.CrossRefGoogle ScholarPubMed
Henry, BA, Rao, A, Ikenasio, BA, Mountjoy, KG, Tilbrook, AJ, Clarke, IJ 2001a. Differential expression of cocaine-and amphetamine-regulated transcript and agouti related-protein in chronically food-restricted sheep. Brain Research 918, 40–50.CrossRefGoogle ScholarPubMed
Henry, BA, Goding, JW, Tilbrook, AJ, Dunshea, FR, Clarke, IJ 2001b. Intracerebroventricular infusion of leptin elevates the secretion of luteinising hormone without affecting food intake in long-term food-restricted sheep, but increases growth hormone irrespective of bodyweight. Journal of Endocrinology 168, 67–77.CrossRefGoogle ScholarPubMed
Henry, BA, Tilbrook, AJ, Dunshea, FR, Rao, A, Blache, D, Martin, GB, Clarke, IJ 2000. Long-term alterations in adiposity affect the expression of melanin-concentrating hormone and enkephalin but not proopiomelanocortin in the hypothalamus of ovariectomized ewes. Endocrinology 141, 1506–1514.CrossRefGoogle Scholar
Henry, BA, Goding, JW, Alexander, WS, Tilbrook, AJ, Canny, BJ, Dunshea, FR, Rao, A, Mansell, A, Clarke, IJ 1999. Central administration of leptin to ovariectomized ewes inhibits food intake without affecting the secretion f hormones from the pituitary gland: evidence for a dissociation of effects on appetite and neuroendocrine function. Endocrinology 140, 1175–1182.CrossRefGoogle Scholar
Hileman, SM, Kuehl, DE, Jackson, GL 1998. Photoperiod affects the ability of testosterone to alter proopiomelanocortin mRNA, but not luteinizing hormone-releasing hormone mRNA, levels in male sheep. Journal of Neuroendocrinology 10, 587–592.CrossRefGoogle Scholar
Iqbal, J, Manley, TR, Ciofi, P, Clarke, IJ 2005. Reduction in adiposity affects the extent of afferent projections to growth hormone releasing hormone and somatostatin neurons and the degree of colocalization of neuropeptides in growth hormone-releasing hormone and somatostatin cells in the ovine hypothalamus. Endocrinology 146, 4776–4785.CrossRefGoogle ScholarPubMed
Iqbal, J, Henry, BA, Pompolo, S, Rao, A, Clarke, IJ 2003. Long-term alterations in bodyweight and food restriction does not affect gene expression of either preproorexin or prodynorphin in the sheep. Neuroscience 118, 217–226.CrossRefGoogle ScholarPubMed
Iqbal, J, Pompolo, S, Dumont, LM, Wu, CS, Mountjoy, KG, Henry, BA, Clarke, IJ 2001a. Long-term alterations in body weight do not affect the expression of melanocortin receptor-3 and -4 mRNA in the ovine hypothalamus. Neuroscience 105, 931–940.CrossRefGoogle Scholar
Iqbal, J, Pompolo, S, Murakami, T, Grouzmann, E, Sakurai, T, Meister, B, Clarke, IJ 2001b. Immunohistochemical characterization of localization of long-form leptin receptor (OB-Rb) in neurochemically defined cells in the ovine hypothalamus. Brain Research 920, 55–64.CrossRefGoogle ScholarPubMed
Iqbal, J, Pompolo, S, Sakurai, T, Clarke, IJ 2001c. Evidence that orexin-containing neurons provide direct input to gonadotropin-releasing hormone neurons in the ovine hypothalamus. Journal of Neuroendocrinology 13, 1033–1041.CrossRefGoogle ScholarPubMed
Kumar, B, Francis, SM, Suttie, JM, Thompson, MP 1998. Expression of obese mRNA in genetically lean and fat selection lines of sheep. Comparative Biochemistry and Physiology – Part B, Biochemistry and Molecular Biology 120, 543–548.CrossRefGoogle ScholarPubMed
Kurose, Y, Iqbal, J, Rao, A, Murata, Y, Hasegawa, Y, Terashima, Y, Kojima, M, Kangawa, K, Clarke, IJ 2005. Changes in expression of the genes for the leptin receptor and the growth hormone-releasing peptide/ghrelin receptor in the hypothalamic arcuate nucleus with long-term manipulation of adiposity by dietary means. Journal of Neuroendocrinology 17, 331–340.CrossRefGoogle ScholarPubMed
Lincoln, GA, Rhind, SM, Pompolo, S, Clarke, IJ 2001. Hypothalamic control of photoperiod-induced cycles in food intake, body weight, and metabolic hormones in rams. American Journal of Physiology – Regulatory, Integrative and Comparative Physiology 281, R76–R90.CrossRefGoogle ScholarPubMed
Marie, M, Findlay, PA, Thomas, L, Adam, CL 2001. Daily patterns of plasma leptin in sheep: effects of photoperiod and food intake. Journal of Endocrinology 170, 277–286.CrossRefGoogle ScholarPubMed
McMahon, CD, Buxton, DF, Elsasser, TH, Gunter, DR, Sanders, LG, Steele, BP, Sartin, JL 1999. Neuropepide Y restores appetite and alters concentrations of GH after central administration to endotoxic sheep. Journal of Endocrinology 161, 333–339.CrossRefGoogle Scholar
McMillen, IC, Edwards, LJ, Duffiels, J, Mülhaüsler, BS 2006. Regulation of leptin synthesis and secretion before birth: implications for early programming of adult obesity. Reproduction 131, 415–427.CrossRefGoogle ScholarPubMed
McShane, TM, May, T, Miner, JL, Keisler, DH 1992. Central actions of neuropeptide-Y may provide a neuromodulatory link between nutrition and reproduction. Biology of Reproduction 46, 1151–1157.CrossRefGoogle ScholarPubMed
McShane, TM, Petersen, SL, McCrone, S, Keisler, DH 1993. Influence of food restriction on neuropeptide-Y, proopiomelanocortin, and luteinizing hormone-releasing hormone gene expression in sheep hypothalami. Biology of Reproduction 49, 831–839.CrossRefGoogle ScholarPubMed
Miller, DW, Findlay, PA, Morrison, MA, Raver, N, Adam, CL 2002. Seasonal and dose-dependent effects of intracerebroventricular leptin on 1 h secretion and appetite in sheep. Journal of Endocrinology 175, 395–404.CrossRefGoogle ScholarPubMed
Miller, DW, Harrison, JL, Bennett, EJ, Findlay, PA, Adam, CL 2007. Nutritional influences on reproductive neuroendocrine output: insulin, leptin, and orexigenic neuropeptide signaling in the ovine hypothalamus. Endocrinology 148, 5313–5322.CrossRefGoogle ScholarPubMed
Miner, JL, Della-Fera, MA, Paterson, JA 1990. Blockade of satiety factors by central injection of neuropeptide Y in sheep. Journal of Animal Science 68, 3805–3811.CrossRefGoogle ScholarPubMed
Miner, JL, Della-Fera, MA, Paterson, JA, Baile, CA 1989. Lateral cerebroventricular injection of neuropeptide Y stimulates feeding in sheep. American Journal of Physiology 257, R383–R387.Google ScholarPubMed
Morrison, CD, Wood, R, McFadin, EL, Whiley, NC, Keisler, DH 2002. Effect of intravenous infusion of recombinant ovine leptin on feed intake and serum concentrations of GH, LH, insulin, IGF-1, cortisol, and thyroxine in growing prepubertal ewe lambs. Domestic Animal Endocrinology 22, 103–112.CrossRefGoogle ScholarPubMed
Morrison, CD, Daniel, JA, Holmberg, BJ, Djiane, J, Raver, N, Gertler, A, Keisler, DH 2001. Central infusion of leptin into well-fed and undernourished ewe lambs: effects on feed intake and serum concentrations of growth hormone and luteinizing hormone. Journal of Endocrinology 168, 317–324.CrossRefGoogle ScholarPubMed
Morrison, CD, Daniel, JA, Hampton, JH, Buff, PR, McShane, TM, Thomas, MG, Keisler, DH 2003. Luteinizing hormone and growth hormone secretion in ewes infused intracerebroventricularly with neuropeptide Y. Domestic Animal Endocrinology 24, 69–80.CrossRefGoogle ScholarPubMed
Mülhaüsler, BS, Adam, CL, Findlay, PA, Duffield, JA, McMillen, IC 2006. Increased maternal nutrition alters development of the appetite regulating network in the brain. FASEB Journal 20, 1257–1259.Google Scholar
Mülhaüsler, BS, McMillen, IC, Rouzaud, G, Findlay, PA, Marrocco, EM, Rhind, SM, Adam, CL 2004. Appetite regulatory neuropeptides are expressed in the sheep hypothalamus before birth. Journal of Neuroendocrinology 16, 502–507.CrossRefGoogle Scholar
Mülhaüsler, BS, Adam, CL, Marrocco, EM, Findlay, PA, Roberts, CT, McFarlane, JR, Kauter, KG, McMillen, IC 2005. Impact of glucose infusion on the structural and functional characteristics of adipose tissue and on hypothalamic gene expression for appetite regulatory neuropeptides in the sheep fetus during late gestation. Journal of Physiology 565, 185–195.CrossRefGoogle Scholar
Parkes, DG 1996. Diuretic and natriuretic actions of melanin concentrating hormone in conscious sheep. Journal of Neuroendocrinology 8, 57–63.CrossRefGoogle ScholarPubMed
Pillon, D, Caraty, A, Fabian-Nys, C, Bruneau, G 2003. Early decrease of proopiomelanocortin but not neuropeptide Y mRNA expression in the mediobasal hypothalamus of the ewe, during the estradiol-induced preovulatory LH surge. General and Comparative Endocrinology 134, 264–272.CrossRefGoogle Scholar
Polkowska, J, Gladysz, A 2001. Effect of food manipulation on the neuropeptide Y neuronal system in the diencephalon of ewes. Journal of Chemical Neuroanatomy 21, 149–159.CrossRefGoogle ScholarPubMed
Polkowska, J, Wańkowska, M, Wójcik-Gładysz, A 2006a. Expression of NPY-immunoreactive neurons in the hypothalamus of the cycling ewe. Folia Histochemica et Cytobiologica 44, 13–16.Google ScholarPubMed
Polkowska, J, Wójcik-Gładysz, A, Wańkowska, M 2006b. The effect of intracerebroventricular infusions of leptin on the immunoreactivity of neuropeptide Y and gonadotropin releasing hormone neurons in the hypothalamus of prepubertal sheep in conditions of short fasting. Journal of Chemical Neuroanatomy 31, 130–138.Google Scholar
Qi, Y, Iqbal, J, Oldfield, BJ, Clarke, IJ 2008. Neural connectivity in the medialbasal hypothalamus of the sheep brain. Neuroendocrinology 87, 91–112.CrossRefGoogle Scholar
Qi, Y, Henry, BA, Oldfield, BJ, Clarke, IJ 2010. The action of leptin on appetite-regulating cells in the ovine hypothalamus: demonstration of direct action in the absence of the arcuate nucleus. Endocrinology 151, 2106–2116.CrossRefGoogle ScholarPubMed
Relling, AE, Pate, JL, Reynolds, CK, Loerch, SC 2010. Effect of feed restriction and supplemental dietary fat on gut peptide and hypothalamic neuropeptide mRNA concentrations in growing wethers. Journal of Animal Science 88, 737–748.CrossRefGoogle ScholarPubMed
Sartin, JL, Wagner, CG, Marks, DL, Daniels, J, McMahon, CD, Obese, FY, Partridge, C 2005. Appetite regulation in sheep: a potential site for therapeutic intervention in disease models. Domestic Animal Endocrinology 29, 446–455.CrossRefGoogle ScholarPubMed
Sartin, JL, Marks, DL, McMahon, CD, Daniel, JA, Levasseur, P, Wagner, CG, Whitlock, BK 2008. Central role of the melanocortin-4 receptors in appetite regulation after endotoxin. Journal of Animal Science 86, 2557–2567.CrossRefGoogle ScholarPubMed
Sartin, JL, Dyer, C, Matteri, R, Buxton, D, Buonomo, F, Shores, M, Baker, J, Osbourne, JA, Braden, T, Steele, B 2001. Effect of intracerebroventricular orexin-B on food intake in sheep. Journal of Animal Science 79, 1573–1577.CrossRefGoogle ScholarPubMed
Schwartz, MW, Woods, SC, Porte, D, Seely, RJ, Baskin, DG 2000. Central nervous system control of food intake. Nature 404, 661–671.CrossRefGoogle ScholarPubMed
Soliman, M, Abdelhady, S, Fattou, I, Ishioka, K, Kitamura, H, Kimura, K, Saito, M 2001. No alteration in serum leptin levels during acute endotoxemia in sheep. Journal of Veterinary Medical Science 63, 1143–1145.CrossRefGoogle ScholarPubMed
Sorenson, A, Adam, CL, Findlay, PA, Marie, M, Thomas, L, Travers, MT, Vernon, RG 2002. Leptin secretion and hypothalamic neuropeptide and receptor gene expression in sheep. American Journal of Physiology – Regulatory, Integrative and Comparative Physiology 282, R1227–R1235.CrossRefGoogle Scholar
Thomas, MG, Gazal, OS, Williams, GL, Stanko, RL, Keisler, DH 1999. Injection of neuropeptide Y into the third cerebroventricle differentially influences pituitary secretion of luteinizing hormone and growth hormone in ovariectomized cows. Domestic Animal Endocrinology 16, 159–169.CrossRefGoogle ScholarPubMed
Thomas, SA, Preston, JE, Wilson, MR, Farrell, CL, Segal, MB 2001. Leptin transport at the blood – cerebrospinal fluid barrier using the perfused sheep choroid plexus model. Brain Research 895, 283–290.CrossRefGoogle ScholarPubMed
Tillet, Y, Batailler, M, Fellman, D 1996. Distribution of melanin-concentrating hormone (MCH)-like immunoreactivity in neurons of the diencephalon of sheep. Journal of Chemical Neuroanatomy 12, 135–145.CrossRefGoogle ScholarPubMed
Valassi, E, Scacchi, M, Cavagnini, F 2008. Neuroendocrine control of food intake. Nutrition, Metabolism and Cardiovascular Diseases 18, 158–168.CrossRefGoogle ScholarPubMed
Wagner, CG, McMahon, CD, Marks, DL, Daniel, JA, Steele, B, Sartin, JL 2004. A role for agouti-related protein in appetite regulation in a species with continuous nutrient delivery. Neuroendocrinology 80, 210–218.CrossRefGoogle Scholar
Whitlock, BK, Daniel, JA, McMahon, CD, Buonomo, VC, Wagner, CG, Steele, B, Sartin, JL 2005. Intracerebroventricular melanin-concentrating hormone stimulates food intake in sheep. Domestic Animal Endocrinology 28, 224–232.CrossRefGoogle ScholarPubMed
Williams, LM, Adam, CL, Mercer, JG, Moar, KM, Slater, D, Hunter, L, Findlay, PA, Hoggard, N 1999. Leptin receptor and neuropeptide Y gene expression in the sheep. Journal of Neuroendocrinology 11, 165–169.CrossRefGoogle ScholarPubMed
Xu, R, Roh, SG, Gong, C, Hernandez, M, Ueta, Y, Chen, C 2003. Orexin-B augments voltage-gated L-type Ca(2+) current via protein kinase C-mediated signaling pathway in ovine somatotropes. Neuroendocrinology 77, 141–152.CrossRefGoogle ScholarPubMed
Xu, R, Wang, Q, Yan, M, Hernandez, M, Gong, C, Boon, WC, Murata, Y, Ueta, Y, Chen, C 2002. Orexin-A augments voltage-gated Ca2+ currents and synergistically increases growth hormone (GH) secretion with GH-releasing hormone in primary cultured ovine somatotropes. Endocrinology 143, 4609–4619.CrossRefGoogle ScholarPubMed
Yildiz, S, Blache, D, Celebi, F, Kaya, I, Saatci, M, Cenesiz, M, Guven, B 2003. Effects of short-term high carbohydrate or fat intakes on leptin, growth hormone and luteinizing hormone secretions in prepubertal fat-tailed Tuj lambs. Reproduction in Domestic Animals 38, 182–186.CrossRefGoogle ScholarPubMed
Zaralis, K, Tolkamp, BJ, Houdijk, JG, Wylie, AR, Kyriazakis, I 2008. Changes in food intake and circulating leptin due to gastrointestinal parasitism in lambs of two breeds. Journal of Animal Science 86, 1891–1903.CrossRefGoogle ScholarPubMed
Zaralis, K, Tolkamp, BJ, Houdijk, JG, Wylie, AR, Kyriazakis, I 2009. Consequences of protein supplementation for anorexia, expression of immunity and plasma leptin concentrations in parasitized ewes of two breeds. British Journal of Nutrition 101, 499–509.CrossRefGoogle ScholarPubMed
Zhang, S, Blache, D, Veroe, PE, Adam, CL, Blackberry, MA, Findlay, PA, Eidne, KA, Martin, GB 2005. Expression of orexin receptors in the brain and peripheral tissues of the male sheep. Regulatory Peptides 124, 81–87.CrossRefGoogle ScholarPubMed