The time at which ovulation occurred on the morning of oestrus in unmated cyclic mice was investigated; the majority housed with males exhibited 4-day cycles and the majority housed in the absence of males exhibited 5-day cycles. Regardless of housing condition or cycle length, most animals ovulated between 03.00 and 08.00 hours (lights on from 05.00 to 19.00 hours) on the morning of oestrus. The majority of animals injected with barbital at 17.00 hours on the day of pro-oestrus did not ovulate, nor did their ovaries contain stimulated follicles on the morning of 'oestrus.' These results suggest that the critical period for the ovulatory release of LH is similar in 4-day cyclic mice housed in the presence of males and 5-day cyclic mice housed in the absence of males.
If the inline PDF is not rendering correctly, you can download the PDF file here.