Abstract
Summary
The incidence of ovulation and number of ova shed in 25-day-old rats induced to ovulate by PMS injection at 22 days of age was significantly reduced by administration of sodium barbital at 1:30 p.m. on the 24th day of life. However, when barbital administration was delayed until 5:30 p.m., ovulation occurred more frequently and the number of ova resembled that of non-barbiturate treated controls. Similarly, hypophysectomy before 1:30 p.m. inhibited ovulation while hypophysectomy between 5:00 and 5:30 p.m. did not. These data are interpreted to mean that ovulating hormone is released from the pituitary gland between 1:30 and 5:30 p.m. on the 24th day of life.
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