Biology of Reproduction, Vol 21, 1115-1124, Copyright © 1979 by Society for the Study of Reproduction

Influence of Photoperiod and Neonatally Administered Androgen on Estrous Cycles and Behavior in Hamsters

¹ Department of Psychology, Tulane University, New Orleans, Louisiana 70118

Transient or permanent disruptions of estrous cycles were studied in golden hamsters injected with oil, 1 or 10 µg testosterone propionate 4 days after birth and reared in rooms maintained on short (6L:18D or 12L:12D) or long (14L:10D) photoperiods. The duration of 2 transient episodes of vaginal acyclicity, one related to age and the other to season, was longer in the animals reared in the short photoperiod conditions and independent of exogenous hormone administered neonatally. A more enduring acyclicity, detected in vaginal smears, started at 250 days. Its age of occurrence was related directly to androgen dosage and inversely to the light/dark ratio. Degree of receptivity, measured after ovariectomy and injection of estradiol benzoate and progesterone, was lower in hamsters injected neonatally with androgen than with oil and in those in short than in long photoperiods. Ovaries of acyclic animals were devoid of corpora lutea; a few were polyfollicular in 14L:10D or 6L:18D conditions. Thus, neonatal administration of androgen induces premature absence of cyclicity in hamsters as it does in rats. Short photoperiods instigate both temporary and permanent loss of estrous cycles. Vaginal smears similar to those of the diestrous stage in combination with ovarian cells with a luteinized appearance suggest that progesterone levels are higher in the acyclic hamster than in the acyclic rat.