Abstract
We previously reported that persistent estrus was induced in rats by PMSG administration at a specified period during the estrous cycle. This was again undertaken to clarify the characteristics of gonadotropin secretion during the persistent estrus induced by PMSG and to investigate the possibility of restoration to the normal cycle by various treatments. During the persistent estrus, the LH levels were lower and the FSH higher than in the controls. Following ovariectomy the LH and FSH secretions were delayed as a negative feedback response. When estradiol was implanted in these rats, LH was secreted as a low positive feedback response. Progesterone and hCG injections induced ovulation and then the restoration of the cycle. However, no copulation occurred when females so treated were paired with male rats for a week. Stimulation of the uterine cervix also failed to restore the normal cycle. Based on these results, the following conclusions were drawn : 1) during the persistent estrus, low negative and positive feedback responses are indicative of abnormal secretion of LH and FSH ; 2) there is an apparent dysfunction of the central nervous system in relation to mating ; and 3) the regular estrous cycle can be restored through appropriate treatments.
