Abstract
Summary
Old female rats in constant estrus were given different treatments in an attempt to induce ovulation. Subcutaneous injections of progesterone for 3 days or epinephrine for 10 days, induced ovulation in 6 out of 10 and 11 out of 22 rats respectively, with normal appearing estrous cycles observed in many epinephrine-treated rats. Electrical stimulation of the preoptic area of the hypothalamus produced ovulation in 3 out of 5 old rats. Injections of reserpine, thyroxine or cyproterone acetate, and cervical stimulation, failed to induce ovulation, whereas ovariectomy resulted in anestrus. These observations suggest that changes in hypothalamic function account for constant estrus in old female rats.
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