Provoked Ovulation or Long-Delayed Pseudopregnancy from Coital Stimuli in Barbiturate-Blocked Rats

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Abstract
When spontaneous release of the ovulation quota of hypophysial gonadotropin was blocked in female rats by pentobarbital or phenobarbital on 2 successive days, 91 of 170 (53.5%) copulated when placed with potent males during the night following proestrus, indicating that estrous behavior does not depend on the proestrous surge of ovulating hormone. Among 74 females that copulated, 14 (19%) became pregnant as the result of ovulations clearly invoked by the copulatory stimulus. This confirms other evidence that "reflex" ovulation can occur in rats under special conditions. In the remaining animals copulation had 2 bizarre effects: the current set of graaflan follicles became atretic instead of ovulating on the third night as expected; pseudopregnancy usually followed the formation of new corpora lutea during the next cyclic estrus 5 or 6 days after the copulatory stimulus. Thus, information from the stimulus was apparently retained within the central nervous system long after being received. Whether prolactin secretion is at once increased and maintained at high level while awaiting formation of competent corpora lutea remains to be determined.