Effects of constant infusion of gonadotrophin-releasing hormone in ovariectomized ewes with hypothalamo-pituitary disconnection: Further evidence for differential control of LH and FSH secretion and the lack of a priming effect

Abstract

Experiments were conducted in ovariectomized ewes after hypothalamo-pituitary disconnection (HPD) (a) to examine LH and FSH secretion during constant infusion of gonadotrophin-releasing hormone (GnRH) or physiological saline and (b) to determine whether or not a constant GnRH background enhances or diminishes pituitary responsiveness to GnRH pulses. Whereas pulsatile GnRH infusions maintained LH and FSH secretion, constant infusions (125 or 250 ng/h) led to the complete cessation of LH secretion and reduced FSH secretion. The rate of decline of plasma FSH concentrations was significantly (P < 0.01) greater in animals receiving 250 ng GnRH/h than in saline-treated animals, whereas that in ani..