Photoperiodic modulation of steroid-induced lordosis in golden hamsters

The photoperiodic modulation of steroid-induced receptive behavior was investigated using ovariectomized female hamsters (Mesocricetus auratus) kept in short (6 hr of light/day) or long (16 hr of light/day) photoperiods. When a low dose of estradiol (E) was used, a significantly larger percentage of animals housed in long days displayed lordosis behavior than did animals housed in short days in tests with intact males as stimuli. This effect of photoperiod was reduced when a high dose of E was employed and was absent when E treatment was supplemented with progesterone. These observations suggest that a reduction in behavioral sensitivity to E may contribute to the reproductive quiescence induced by short photoperiods.