A Significant Role of Leptin in the Generation of Steroid-Induced Luteinizing Hormone and Prolactin Surges in Female Rats

Abstract

Recent evidence suggests that leptin, the product of obese (ob) gene, may play an important role in the regulation of reproductive function. However, a possible role of leptin in the preovulatory surges of luteinizing hormone (LH) and prolactin (PRL) in rodents has yet to be explored, and thus examined in this study. Experiments were performed on both normally fed and 3-day starved rats, which were ovariectomized and primed with estradiol and progesterone. At 11:00 h on the day of the experiments, normally fed rats received an intracerebroventricular injection of artificial cerebrospinal fluid, anti-leptin serum, or normal rabbit serum. Three-day starved rats were given artificial cerebrospinal fluid or recombinant human leptin (2.5 μg) via the same route. From 11:00 to 18:00 h, blood was collected every 30 min to measure LH and PRL. The 3-day starvation completely abolished both LH and PRL surges, but leptin resumed these hormonal surges to the levels of normally fed rats. In addition, anti-leptin serum given to normally fed rats significantly depressed LH surge and delayed the onset of PRL surge. This study is the first to demonstrate that leptin plays a physiologically important role in the generation of steroid-induced LH and PRL surges in female rats.