Leptin acts centrally to induce the prepubertal secretion of luteinizing hormone in the female rat: a potential early role in the pubertal process

Abstract

Recent data generated from adult male and female rats indicates that lepton is capable of stimulating luteinizing hormone (LH) secretion via a hypothalamic action. Consequently, we hypothesized that this peptide may similarly play a role in controlling LH secretion during late juvenile and peripubertal development, hence contributing to hypothalamic-pituitary function during sexual maturation. Therefore, this study was conducted to determine if lepton is capable of stimulating LH release during this critical time of development and, if so, to determine whether this action is due to an effect at the hypothalamic level. Results showed that lepton, when administered directly into the third ventricle (3V) of the brain, can stimulate (P<0.01) LH release in late juvenile animals at doses of 0.01-1.0[]g. A higher dose of 10[]g was ineffective in stimulating LH release. Immunoneutralization of luteinizing hormone-releasing hormone (LHRH) via 3V administration of LHRH antiserum to late juvenile animals indicated a hypothalamic site of action, since the leptin-induced LH release was blocked in the animals that received anti-tell-RH, but not in the control animals that received normal rabbit serum. Leptin did not significantly stimulate LH release from animals in first proestrus, estrus or fiestas. We also report that the serum levels of lepton increase (P<O.O5) during the late juvenile period of development, then decrease (P<0.05) once the animal enters the peripubertal period. Collectively, our results show that leptin is capable of acting centrally to stimulate LH release during late juvenile development, a time when serum lepton levels were shown to be elevated. Also, our results suggest that since lepton did not simulate LH release during the peripubertal phase of development, the peptide likely plays an early role in the pubertal process.