Triggering of Ovulation by Coitus in the Rat

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Publisher Summary Demonstration of the ovulatory action of early coitus during the estrous cycle in the rat and of the fertilizability of the oocytes thus ovulated in 5-day cyclic rats has essentially biological significance. It shows that the neural structures involved in determining spontaneous ovulation in the rat, structures normally activated by environmental and hormonal factors, can, as in reflex ovulators, be activated by coital stimulus. There is therefore no sharp borderline between reflex and spontaneous ovulators. The rat plays a pre-eminent role among laboratory rodents because of its extensive use in experiments concerning neural factors involved in spontaneous ovulation. The chapter determines if coitus could play a physiological role during the reproductive cycle in the rat. Three conditions essential for the study of the ovulatory action of coitus in physiological conditions (that is, during the estrous cycle in the rat). First, a precise determination of the beginning of spontaneous ovulation in female rats is made, even though different estimates already existed on this point. Second, conditions favorable to the induction of precocious sexual receptivity in female rats during the cycle. Third, choice of an accurate criterion of ovulation that would clearly distinguish between the ovulatory and the luteotropic effects of coitus. Beyond its biological implications, demonstration of the ovulatory action of coitus in the rat has methodological interest as a potential means of studying various factors in mammalian ovulation.