Abstract
Male pheromones in ruminant species such as sheep and goats are known to reactivate quiescent ovarian function in seasonally anestrous females. We have previously shown that only a few minutes exposure to the male pheromone can accelerate the GnRH pulse generator activity immediately in the female goat. In this study the effect of 4 h continuous exposure to the male pheromone on the GnRH pulse generator activity was examined by recording the specific multiple unit acitivity (MUA) from the medial basal hypothalamus. Pooled buck hair was used as the source of male pheromone. Six ovariectomized estradiol-primed does were fitted with a nose-mask for 8 h, and during the latter 4 h period 2.0 g of pooled male hair was set in the chamber at the rostral end of the mask. As compared with the period when only an empty mask was put on, the exposure to the male hair resulted in a shortening (p<0.05) of the interval between the MUA volleys, namely the electrophysiological manifestation of the pulsatile GnRH neurosecretion. This stimulatory effect was observed throughout the time when animals were exposed to the male pheromone. This result demonstrates that the hypothalamic GnRH pulse generator of the recipient female is accelerated as long as the exposure to the male pheromone continues.
