SUMMARY
The effects of an injection of pregnant mares' serum (PMS), human chorionic gonadotrophin (HCG), or of superovulation treatment with both of these gonadotrophins on subsequent reproductive behaviour of adult mice and on their response to a second superovulation treatment given shortly afterwards have been studied.
An injection of PMS had induced ovulation, but not superovulation, in dioestrous mice autopsied 24 hr later. The injection also induced oestrus and superovulation in many mice (c. 30%) 60–62 hr later, a positive correlation being found between mating and ovulation in these mice. The resumption of the natural oestrous cycle after an injection of PMS was delayed in some of the mice. HCG had induced ovulation in mice in metoestrus-II and dioestrus autopsied 24 hr later. Most mice quickly resumed their natural oestrous cycle after the injection of HCG.
If mice were not paired with males after the full superovulation treatment with PMS and HCG, they resumed their natural oestrous cycle within 3–6 days. Ovulation, fertilization and pregnancy during or after this natural oestrus were quite normal. These mice were also capable of further induced oestrus and superovulation when given a second course 1–3 days after the first treatment, though the number of mice that ovulated was lower, and the variability between mice in the number of eggs ovulated was higher, if the second treatment was given 1–2 days after the first.
The corpora lutea formed in mice that mated after a superovulation treatment were fully active. A second treatment induced superovulation in most mice, but failed to induce oestrus in the majority of them, especially when given during mid-pseudopregnancy. Fertilization and embryonic development were quite normal in the few mice that mated.
Studies on the Oestrous Cycle of Camel (Camelus dromedarius)
