Leptin can act as a satiety factor and exert neuroendocrine effects, but most studies have been performed in fasted animals. We aimed to determine the effect of chronic under-nutrition on the response to a 3-day intracerebroventricular infusion of leptin with regard to food intake and the secretion of pituitary hormones. Ovariectomised ewes (n=6) had a mean (+/-s.e.m. ) bodyweight of 56+/-0.8 kg on a diet available ad libitum (ad lib) or 33.4+/-1 kg on a restricted diet. The differential bodyweight was achieved by dietary means over a period of 6 months prior to the commencement of the study. Leptin (4 microg/h) or vehicle (artificial cerebrospinal fluid (aCSF)) was infused into the third cerebral ventricle for 3 days. Blood samples were taken prior to commencement and on day 3 of infusion for the assay of plasma hormone levels. The experiment was repeated one week later in a cross-over design. Food intake and metabolic status were monitored daily. The luteinising hormone (LH) pulse amplitude was lower (P<0.05) but plasma growth hormone (GH) levels were higher (P<0.05) in the food-restricted animals. Plasma levels of glucose, lactate, insulin, urea and triglycerides were similar in the two groups but non-esterified fatty acid levels were higher (P<0.01) in the animals on an ad lib diet. Leptin reduced (P<0.05) food intake only in the animals fed an ad lib diet. Leptin increased (P<0.05) the secretion of LH in the food-restricted group only and increased (P<0.05) GH irrespective of bodyweight. In conclusion, leptin does not alter food intake in animals on a restricted diet but can increase the secretion of LH in the same animals. The treatment of leptin was not sufficient to reduce plasma GH levels in the food-restricted animals, suggesting that other factors or mechanisms must be involved in the regulation of this axis.

This article has been cited by other articles:

				C. L. Adam, P. A. Findlay, and D. W. Miller Blood-Brain Leptin Transport and Appetite and Reproductive Neuroendocrine Responses to Intracerebroventricular Leptin Injection in Sheep: Influence of Photoperiod Endocrinology, October 1, 2006; 147(10): 4589 - 4598. [Abstract] [Full Text] [PDF]

				H. Kadokawa, D. Blache, and G. B. Martin Plasma leptin concentrations correlate with luteinizing hormone secretion in early postpartum Holstein cows. J Dairy Sci, August 1, 2006; 89(8): 3020 - 3027. [Abstract] [Full Text] [PDF]

				C R. Barb, R. R Kraeling, G. B Rampacek, and G. J Hausman The role of neuropeptide Y and interaction with leptin in regulating feed intake and luteinizing hormone and growth hormone secretion in the pig. Reproduction, June 1, 2006; 131(6): 1127 - 1135. [Abstract] [Full Text] [PDF]

				M Mitchell, D T Armstrong, R L Robker, and R J Norman Adipokines: implications for female fertility and obesity Reproduction, November 1, 2005; 130(5): 583 - 597. [Abstract] [Full Text] [PDF]

				J. Iqbal, T. R. Manley, P. Ciofi, and I. J. Clarke 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 of the Ovine Hypothalamus Endocrinology, November 1, 2005; 146(11): 4776 - 4785. [Abstract] [Full Text] [PDF]

				Z A Archer, S M Rhind, P A Findlay, C E Kyle, M C Barber, and C L Adam Hypothalamic responses to peripheral glucose infusion in food-restricted sheep are influenced by photoperiod J. Endocrinol., March 1, 2005; 184(3): 515 - 525. [Abstract] [Full Text] [PDF]

				I. J. Clarke, K. Backholer, and A. J. Tilbrook Y2 Receptor-Selective Agonist Delays the Estrogen-Induced Luteinizing Hormone Surge in Ovariectomized Ewes, but Y1-Receptor-Selective Agonist Stimulates Voluntary Food Intake Endocrinology, February 1, 2005; 146(2): 769 - 775. [Abstract] [Full Text] [PDF]

				G. N. Wade and J. E. Jones Neuroendocrinology of nutritional infertility Am J Physiol Regulatory Integrative Comp Physiol, December 1, 2004; 287(6): R1277 - R1296. [Abstract] [Full Text] [PDF]

				M. N. Maciel, D. A. Zieba, M. Amstalden, D. H. Keisler, J. P. Neves, and G. L. Williams Chronic administration of recombinant ovine leptin in growing beef heifers: Effects on secretion of LH, metabolic hormones, and timing of puberty J Anim Sci, October 1, 2004; 82(10): 2930 - 2936. [Abstract] [Full Text] [PDF]

				D.A. Zieba, M. Amstalden, S. Morton, M.N. Maciel, D.H. Keisler, and G.L. Williams Regulatory Roles of Leptin at the Hypothalamic-Hypophyseal Axis Before and after Sexual Maturation in Cattle Biol Reprod, September 1, 2004; 71(3): 804 - 812. [Abstract] [Full Text] [PDF]

				G. S. Fraley, J. M. Scarlett, I. Shimada, D. N. Teklemichael, B. V. Acohido, D. K. Clifton, and R. A. Steiner Effects of Diabetes and Insulin on the Expression of Galanin-Like Peptide in the Hypothalamus of the Rat Diabetes, May 1, 2004; 53(5): 1237 - 1242. [Abstract] [Full Text] [PDF]

				M.N. Maciel, D.A. Zieba, M. Amstalden, D.H. Keisler, J.P. Neves, and G.L. Williams Leptin Prevents Fasting-Mediated Reductions in Pulsatile Secretion of Luteinizing Hormone and Enhances Its Gonadotropin-Releasing Hormone-Mediated Release in Heifers Biol Reprod, January 1, 2004; 70(1): 229 - 235. [Abstract] [Full Text] [PDF]

				M. E. Wilson, J. Fisher, K. Chikazawa, R. Yoda, A. Legendre, D. Mook, and K. G. Gould Leptin Administration Increases Nocturnal Concentrations of Luteinizing Hormone and Growth Hormone in Juvenile Female Rhesus Monkeys J. Clin. Endocrinol. Metab., October 1, 2003; 88(10): 4874 - 4883. [Abstract] [Full Text] [PDF]

				I. J. Clarke, A. Rao, Y. Chilliard, C. Delavaud, and G. A. Lincoln Photoperiod effects on gene expression for hypothalamic appetite-regulating peptides and food intake in the ram Am J Physiol Regulatory Integrative Comp Physiol, January 1, 2003; 284(1): R101 - R115. [Abstract] [Full Text] [PDF]

				M. L. Barker-Gibb, A. Sahu, C. R. Pohl, and T. M. Plant Elevating Circulating Leptin in Prepubertal Male Rhesus Monkeys (Macaca mulatta) Does Not Elicit Precocious Gonadotropin-Releasing Hormone Release, Assessed Indirectly J. Clin. Endocrinol. Metab., November 1, 2002; 87(11): 4976 - 4983. [Abstract] [Full Text] [PDF]

				H. Watanobe and S. Habu Leptin Regulates Growth Hormone-Releasing Factor, Somatostatin, and alpha -Melanocyte-Stimulating Hormone But Not Neuropeptide Y Release in Rat Hypothalamus In Vivo: Relation with Growth Hormone Secretion J. Neurosci., July 15, 2002; 22(14): 6265 - 6271. [Abstract] [Full Text] [PDF]