Olfactory bulbectomy prevents short photoperiod-induced anestrus in female golden hamsters

Abstract

When female golden hamsters are maintained on a photoperiod of less than 12.5 h of light per day, they go into a pineal gland-induced anestrus in 6–10 weeks. This acyclicity is similar in certain respects to the testicular regression which occurs in male golden hamsters maintained on a short photoperiod. A recent study has indicated that pre-pubertal olfactory bulbectomy (BX) will prevent the testicular regression in adult male hamsters exposed to a short photoperiod. The present study tested the effect of pre-pubertal or adult BX on the anestrus associated with maintenance of adult female golden hamsters on short photoperiod. In Expt. 1, hamsters were pre-pubertally sham BX (SH) or BX (23–25 days of age) and then maintained on LD 14:10 or LD 6:18 for 15 weeks. In Expt. 2, hamsters were SH or BX as adults (63–65 days of age) and maintained on LD 6:18 for 13 weeks. The estrous cycles of all animals were monitored on a daily basis. In Expt. 1, all animals on LD 14:10 had regular estrous cycles for the duration of the study. Sixty percent of the SH group on LD 6:18 became anestrous, whereas 87.5% of the BX group on LD 6:18 continued having regular cycles. In Expt. 2, 80% of the SH group became anestrous while 90% of the BX group continued having regular estrous cycles. The possible mechanisms whereby BX affects the cyclicity of female hamsters is discussed. The fact that BX resulted in increased morning gonadotropin levels and ovarian weight in animals on LD 14:10, as well as in the hamsters on short photoperiod, suggests that there is a relationship between the olfactory bulb and the reproductive system that is independent of the photoperiod, in addition to more dramatic effects of olfaction on reproduction in animals on a short photoperiod.