A significant participation of orexin-A, a potent orexigenic peptide, in the preovulatory luteinizing hormone and prolactin surges in the rat

Orexins are novel hypothalamic peptides which stimulate food intake. In view of the well-known tight connection between the nutritional state and the reproductive function, in this study we examined a possible role of orexin-A in the generation of ovarian steroid-induced luteinizing hormone (LH) and prolactin (PRL) surges in ovariectomized rats. Experiments were performed on both normally-fed and 3-day-fasted rats. Although fasting led to abolition of both LH and PRL surges, intracerebroventricular administration of orexin-A (0.3 and 3.0 nmol) resulted in a dose-dependent recovery of the hormonal surges. In addition, anti-orexin-A antisera given to normally-fed rats completely abrogated the surges of both hormones. These results demonstrate for the first time a significant participation of orexin-A in the preovulatory LH and PRL surges in the rat. (C) 2001 Elsevier Science B.V. All rights reserved.