Effects of neuropeptide Y (NPY), galanin and vasoactive intestinal peptide (VIP) on pituitary hormone release and on ovarian steroidogenesis.

Ovarian folliculogenesis is regulated by the gonadotrophins, but in recent years other peptides have been found to serve as local regulators of ovarian function. The aim of this study is to evaluate the effects of NPY, galanin and VIP on pituitary and gonadal hormone release. Effects of NPY, galanin and VIP on progesterone, estradiol production by cultured rat granulosa and effects of these peptides on pituitary hormone release by cultured pituitary cells were examined according to methods previously described. Maximal effects of NPY, galanin and VIP on pituitary hormone release and on gonadal steroids were observed after administration of 10 nM of these peptides during 60 mins incubation. VIP and NPY, but not galanin, stimulated PRL release from cultured pituitary cells. VIP increased also LH release whenever NPY and galanin did not change LH release from pituitary cells. Galanin, but not NPY and VIP, leads to an increase of GH production. VIP, NPY and galanin did not change TSH and FSH release. NPY, galanin and VIP markedly stimulated progesterone release from cultured granulosa cells. NPY, galanin and VIP did not change estradiol and testosterone release. Conclusions. Direct effects of NPY, galanin and VIP on pituitary hormone release may indicate their role in the mechanism of pituitary hormone release. A marked increase of progesterone from cultured granulosa cells after VIP, NPY and galanin suggests that these peptides may be involved in the local ovarian steroidogenesis.