α-Melanocyte stimulating hormone and the release of sex attractant odors in the female rat

Abstract

Sexually experienced male rats were used to test the attractiveness of odors of hypophysectomized females the male rats showed a clear preference for 4 days failed to alter the attractiveness of odors of hypophysectomized females and male rats showed a clear preference for the odors of females that had received 10 micrograms EB. Daily administration of 50 micrograms alpha-MSH failed to increase the attractiveness of odors of hypophysectomized females the male rats showed a clear preference for the odors of females that had received 10 micrograms EB. Daily administration of 50 micrograms alpha-MSH failed to increase the attractiveness of odors from females that received 2 microgram EB but was effective in females that had received 10 micrograms EB. However, no effect was seen in female rats that had been preputialectomized. alpha-MSH also increased the attractiveness of odors of posterior hypophysectomized rats in proestrus. Moreover, the reduction in odor attractiveness found after posterior hypophysectomy in female rats in proestrus was almost restored by alpha-MSH treatment. On the other hand, when the alpha-MSH treated posterior hypophysectomized females were in diestrus their odors were less attractive to male rats than those of the untreated controls. A similar reduction in odor attractiveness occurred in alpha-MSH treated posterior hypophysectomized females in proestrus after a single injection of progesterone. These results suggest that in the female rat alpha-MSH has a physiological role in controlling sexual odors from the preputial glands and by interacting with estrogen and progesterone can either enhance or reduce the attractiveness of these odors to male rats.