Vaginal Cytology, Induced Ovulation and Gestation in the Squirrel Monkey (Saimiri sciureus)

Abstract

A study designed to analyze changes in vaginal cytology of the squirrel monkey (Saimiri sciureus) during the ovulatory and anovulatory seasons in the presence or absence of exgenous hormonal stimulation is presented. There were 2 spring sessions April 9-May 9 and May 16-June 16 in which treated animals received a standard ovulation induction regimen consisting of 5 days pretreatment with progesterone followed by 4 days of follicle stimulating hormone (FHS) with 500 IU of human chorionic gonadotropin (HCG) given on the evening of the last FSH injection. The squirrel monkey is unresponsive to this method during the summer months so that a different regimen is used. This consists of 4 days of estradiol followed by progesterone and the standard ovulation induction regimen given above. Laparoscopic examinations were carried out 22 days after the administration of HCG. Daily observations were made 3 times during each day to study the sexual behavior of treated and control animals. Vaginal smears were collected every other day from all animals beginning on the day of 1st hormonal injections in the treated animals. There was a total absence of menstruation. During the spring season the attempts to mate were greatest on the day following HCG administration with a secondary rise 8 days later. During the 1st summer session the attempts to mate were again highest immediately following HCG but at a level only 1/3 of the spring session. A secondary rise took place 15 days later. But the last summer session showed that attempts to mate were only made on the day after HCG injection. During the spring season 6 of 8 treated and 5 of 9 control females ovulated at least once. 2 treated and 4 control females become pregnant. During the summer season 3 of 6 treated animals and 3 of 7 control animals ovulated at least once. 2 treated and 4 control females became pregnant. It is suggested that there is a decreased responsiveness of squirrel monkeys to FSH stimulation during the summer months.