Mammalian Reproductive Pheromone : Isolation and Study on Central Action

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In this study, the neurophysiological bioassay system for mammalian reproductive pheromones has been established by means of hypothalamic multipleunit activiry (MUA) recording, by which the GnRH pulse generator activity can be monitored conveniently. The porposes of the present study were [1] to purify the pheromonal substance responsible for the "male effect" known in domestic ruminant species such as sheep and goats, and [2] reveal the central mechanism of pheromone actions which not only stimulate reproductive activities but also modify various other behaviors including feeding and exploring. Obtained results can be summarized as follows.Recording electrodes were stereotaxically placed in the medial basal hypothalamus of ovariectomized goats, which were subcutaneously implanted with estradiol containing capsules to keep steroidal milieu constant. The specific MUA volleys, which coincided with LH pulses in the peripheral circulation, were regarded as the electrophysiological manifest … More ation of the GnRH pulse generator activity. The exposure of the tested-goat to hair sample, or its ether extract, obtained from sexually-active male goats resulted in the accleleration of the GnRH pulse generator activity, clearly indicating the existence of primer-pheromone activity. On the other hand, hair samples from castrated male did not have such a progonadal activity, which was then resumed after treating the castrated one with testosterone for several weeks. Sebaceous gland was suggested to be the potential source of androgen dependently produced male pheromones.In addition to single (short-term) appliation, more prolonged exposure (e.g.4 hours continuously) to pheromes was also effective in terms of stimulating the reproductive neuroendocrine system. Another interesting finding was that the goat developed a state of reflactory to the pheromonal stimulation following continuous exposure for several hours. Based on the neurophysiological bioassay means developed in this study, the isolation study of pheromone (s) is proceeding. Less