Depressant Effects of Sexual Rest on Reproductive Behavior and Physiology in Male Rats

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Abstract
Previous studies have shown that sexual experience stimulates reproductive behavior and physiology in male rats. The purpose of the present study was to determine the effects of sexual rest on the reproductive behavior and physiology of sexually experienced, male rats. Sexual experience was provided by five single-ejaculation mating tests. On the fifth mating test, the males were individually paired with a virgin, naturally estrous rat. Mating behavior and sperm transport were measured. Males were then randomly assigned to one of two groups. The group designated Sexually Active was mated 14 times during the subsequent 42 days. The other group of males was termed Sexually Rested during that 42 day period. On Day 46, all males were individually paired with a virgin, naturally estrous rat. Mating behavior and sperm transport were again measured. The behavioral measures revealed that sexual rest depressed the inter-intromission interval and ejaculation latency in sexually experienced males. In addition, sperm transport within the female reproductive tract was also reduced in females mated with Sexually Rested males. The weight of selected reproductive tissues in Sexually Active and Sexually Rested groups, and in a group of Sexually Inexperienced males was also determined. Sexual rest depressed the weight of the seminal vesicles, but not of the d. bulbocavernosus. However, the weight of both the seminal vesicles and d. bulbocavernosus of Sexually Rested rats was still greater than that of Sexually Inexperienced rats. The results of this experiment demonstrate that sexual rest causes a decline in measures of both reproductive behavior and physiology. The relevance of these findings to the lowered fecundity of seasonal breeders, at the start of the breeding period, is discussed.