Development of a practical means for pheromonal manipulation of reproduction.

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The aim of this study was to collect necessary information for the development of feasible measures of artificially manipulating reproductive endocrine function of domestic ruminants by using their naturally-produced pheromones.We focused on the pheromone (s) responsible for the "male effect", a phenomenon known as the ovarian reactivation induced by male pheromones in seasonally anestrous ewes and does. As the first step of approach, a specific bioassay system was established. Namely, the electrophysiological manifestation of the hypothalamic GnRH pulse generator activity was monitored from conscious ovariectomized goats by recording the multiple unit activity (MUA). The existence of primer pheromone activity was assessed based on the observation whether of not the exposure to tested-material resulted in an acceleration of the GnRH pulse generator activity in ovariectomized goats, which had been primed with estradiol and kept under 16L8D photoperiod.By means of this specific bioassay we were able to show that ether extracts from hair or skin samples obtained from head and/or neck regions possess strong pheromone activity in terms of stimulating the hypothalamic GnRH pulse generator. Thus identified pheromonal substances were also shown to be produced androgen dependently at the sebaceous glands of male goats, and the molecular weight of these volatile pheromones would be less than 400. The present results strongly suggest that pheromone (s) responsible for the male effect in sheep and goats is a molecule which largely shares chemical characteristics with either fatty acids or steroid delivertives. The information obtained in this study appears essential for further purifying mammalian pheromones.