Leptin acts centrally to induce the prepubertal secretion of luteinizing hormone in the female rat

Recent data generated from adult male and female rats indicates that leptin is capable of stimulating luteinizing hormone (LH) secretion via a hypotha lamic action. Consequently, we hypothesized that this peptide may similarly play a role in controlling LH secretion during late juvenile and peripuber tal development; hence, contributing to hypothalamic-pituitary function dur ing sexual maturation. Therefore, this study was conducted to determine if leptin is capable of stimulating LH release during this critical time of de velopment and, if so, to determine whether this action is due to an effect at the hypothalamic level. Results showed that leptin, when administered di rectly into the brain third ventricle (3V), can stimulate (P < 0.01) LH rel ease in late juvenile animals at doses of 0.01-1.0 mu g. A higher dose of 1 0 mu g was ineffective in stimulating LH release. Immunoneutralization of l uteinizing hormone-releasing hormone (LHRH) via 3V administration of LHRH a ntiserum to late juvenile animals indicated a hypothalamic site of action, since the leptin-induced LH release was blocked in the animals that receive d anti-LHRH, but not in the control animals that received normal rabbit ser um. Leptin did not significantly stimulate LH release from animals in first proestrus, estrus, or diestrus. We also report that the serum levels of le ptin increase (P < 0.05) during the late juvenile period of development, th en decrease (P < 0.05) once the animal enters the peripubertal period. Coll ectively, our results show that leptin is capable of acting centrally to st imulate LH release, but only during late juvenile development; thus, we sug gest the peptide likely plays a facilitatory role on late juvenile LH secre tion, but does not drive the LHRH/LH releasing system to first ovulation an d hence, sexual maturity. (C) 2000 Elsevier Science inc. All rights reserve d.