TIMING OF LH RELEASE AND OVULATION IN THE CYCLIC MOUSE

Abstract

Summary. The time at which ovulation occurred on the morning of oestrus in unmated cyclic mice was investigated. Ovulation was found to occur during the late part of the dark period and early part of the light period (lights on from 05.00 to 19.00 hours). Barbital was administered at different times before the expected time of ovulation in an effort to determine the time of the ovulatory release of lh. Barbital injection at 17.00 hours, but not at 21.00 hours, on the day of pro-oestrus prevented the appearance of ovarian evidence of lh release as indicated by the absence both of ovulation and of stimulated follicles.