Influence of Copulation on Ovulation in the Cycling Rat

Abstract

Female rats with a record of regular 4-day estrous cycles received different quantities of coital stimulation at specified times on the afternoon of proe3trus. The effects of copulation on numbers of ova ovulated were evaluated on the following morning of estrus between 0930 and 1055. The results show that the amount of copulation received between the hours of 1230 and 1730 failed to produce increases in the normal number of ova ovulated. If, however, intromissions were received between 1750 and 1830 on the afternoon of proestrus, there were increased numbers of ova released. It was suggested that the increases result from an additional release of LH acting on mature follicles which would not ordinarily ovulate. Those subjects responding early in the afternoon had significantly higher uterine weights than those responsive later, suggesting a relationship between high preovulatory estrogen titers and the timing of sexual behavior. The present experiment provides evidence that, if the mating stimulus is pro...