Inhibitory effect of pituitary adenylate cyclase activating polypeptide on the initial stages of rat follicle development.

Pituitary adenylate cyclase activating polypeptide (PACAP) is transiently expressed in preovulatory follicles of different species and positively affects parameters correlated with the ovulatory process. It has also been shown to be expressed in the interstitial tissue and in interstitial glandular cells in the proximity of primordial and preantral follicles. The aim of the present study was to investigate whether PACAP influences the recruitment of primordial follicles and the growth and differentiation of preantral follicles. Rat ovaries from 2-day-old animals were cultured for 5 days in the presence of PACAP. This treatment significantly inhibited the primordial to primary follicle transition. PACAP inhibited granulosa cell proliferation without affecting cell viability. PACAP also inhibited the growth of isolated preantral follicles cultured under basal conditions or in the presence of follicle-stimulating hormone (FSH). These results suggest that PACAP is significantly involved in the cyclic recruitment of primordial follicles and in the FSH-dependent growth of preantral follicles.