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Galanin-Like Peptide as a Possible Link between Metabolism and Reproduction in the Macaque

Graduate Program in Neurobiology and Behavior (M.J.C.) and Departments of Physiology and Biophysics (M.J.C., R.A.S.) and Obstetrics and Gynecology (J.M.S., D.K.C., R.A.S.), University of Washington, Seattle, Washington 98195; Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine (M.S., T.M.P.), Pittsburgh, Pennsylvania 15261; and Division of Neuroscience, Oregon National Primate Research Center (K.L.G., J.L.C., M.S.S.), Beaverton, Oregon 97006

Address all correspondence and requests for reprints to: Dr. Robert A. Steiner, Department of Physiology and Biophysics, University of Washington, Box 357290, Seattle, Washington 98195-7290. E-mail: steiner{at}u.washington.edu.

Galanin-like peptide (GALP) is a hypothalamic neuropeptide that has been implicated in the control of feeding, metabolism, and reproduction. The goal of this study was to examine the effects of central infusions of GALP on GnRH and LH secretion and to identify physiological factors that influence the expression of GALP mRNA in the brain of a primate species. Infusions of GALP into the lateral cerebroventricle of the macaque caused a significant increase in LH secretion, which was blocked by administration of the GnRH receptor antagonist acyline. However, the expression of GALP mRNA in the arcuate nucleus, as determined by in situ hybridization, was not regulated by either estradiol or progesterone. Compared with feeding ad libitum, fasting for 48 h produced a significant reduction in the hypothalamic expression of GALP mRNA. GALP neurons were found to express both neuropeptide Y Y1 receptor and serotonin 2C receptor by double-label in situ hybridization. Taken together, these results suggest that GALP neurons play a role of integrating metabolic signals, which are relayed to circuits controlling GnRH release in the macaque.

This work was supported by the NICHD, National Institutes of Health, through cooperative agreement (U54-HD-012629, U54-HD-18185, and U54-HD-08610) as part of the Specialized Cooperative Centers Program in Reproductive Research as well as by Grants R01-DK-061517, R01-HD-027142, R01-HD-13254, NSF 0110686, P01-DK-055819, P51-RR-000163, and R01-MH-062677.

Abbreviations: aCSF, Artificial cerebrospinal fluid; Arc, arcuate nucleus; BW, body weight; E, estradiol; GALP, galanin-like peptide; 5-HT2C, serotonin 2C; ICV, intracerebroventricular; ISH, in situ hybridization; NPY, neuropeptide Y; P, progesterone; POMC, proopiomelanocortin; RNase, ribonuclease; SBR, signal to background ratio.

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