Isolation and Characterization of Mammalian Reproductive Pheromones

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It has been well-known that the chemical communication through the olfactory system between individual animals plays an essential role in various aspects of reproductive behavior in mammals, such as territorial behavior, mating behavior and maternal behavior. Isolation and characterization of pheromone molecules are, therefore, important not only because the obtained information can be readily applied to improving the reproductive efficiency and solving reproductive problems in domestic animals but also because the isolated or synthesized pheromones could be used as potent tools in the research field of neuroscience for studying the mystery of brain functions. Unlike in invertebrate species, however, the research on mammalian pheromones has not yet been advanced much so far mainly due to the lack of appropriate bioassay system to assess the pheromonal activity in higher vertebrates such as mammalian species.In the present study, we have established a novel bioassay system with high specificity and reproducibility for mammalian reproductive pheromones, known as the cause of "male effect" in domestic ruminant, using the electrophysiological manifestation of hypothalamic GnRH pulse generator activity as a parameter. By using this unique bioassay, we have been able to demonstrate that the odor of male goat hair or its ether extract accelerates GnRH pulse generator instantaneously in ovariectomized goats treated with estradiol and kept under longday photoperiod. In contrast, hair odor from castrated goats had no effect indicating the androgen dependent production and secretion of pheromones. Since the application of pheromone substance can be accurately timed in relation to the GnRH pulses and also the effect can be assessed on the real-time basis, this procedure will provide us with opportunity to isolate mammalian pheromones. Further study for the chemical characterization of substance (s) is now ongoing.