Exposure to ram wool stimulates gonadotropin-releasing hormone pulse generator activity in the female goat

Abstract

In the sheep and goat, exposure of anestrous females to a conspecific male odor enhances reproductive activity. Interestingly, a previous report indicated that male goat hair stimulated pulsatile luteinizing hormone (LH) secretion in the ewe. In the present study, we addressed whether ram wool affects the gonadotropin-releasing hormone (GnRH) pulse generator activity in the female goat. Five ovariectomized (OVX) goats were chronically implanted with recording electrodes in the mediobasal hypothalamus, and manifestations of the GnRH pulse generator were monitored as characteristic increases in multiple-unit activity (MUA volleys). Wool or hair samples were collected from a mature ram, ewe and male goat, and their effects on the MUA volley were examined. The exposure to ram wool induced an MUA volley within 1 min in all five OVX goats, as did the exposure to male goat hair. The ewe wool had no effect on the timing of an MUA volley occurrence. An invariable association of MUA volleys with LH pulses in the peripheral circulation was also confirmed in two OVX goats exposed to ram wool. The present results clearly indicate that exposure to ram wool stimulates pulsatile GnRH/LH release in the female goat. Since exposure to male goat hair enhances pulsatile LH secretion in the ewe, it is likely that very similar, if not identical, molecules are contained in the male-effect pheromone in the sheep and goat.