Influence of Photoperiod on Reproductive Development in the Golden Hamster

Abstract

The effect of early lighting conditions on the sexual development of male and female golden hamsters was investigated, utilizing 2 experimental paradigms. In the first, hamsters were exposed to 1 of several daily light cycles (14L[h of light]:10D[h of dark], 6L:18D, 1L:23D or constant darkness) from birth to 7 wk of age. Weekly measurements of gonadal and sex accessory organ weights demonstrated similar rates of reproductive development among treatment groups, indicating that the onset of puberty apparently is not photoperiodically controlled. In the 2nd experiment, hamsters blinded at birth and exposed for 13 wk to short- vs. long-day photoperiods (6L:18D or 14L:10D) were compared with sighted control animals on the same lighting schedules. Neither photoperiod nor blinding influenced the rate of reproductive organ growth up to 7 wk of age. After this time, in contrast to the continued reproductive growth of photostimulated (14L:10D) sighted hamsters, regression was observed in the light-deprived animals, with the kinetics of regression differing among the treatment groups. Complete reproductive atrophy of the blinded males occurred sooner on long- than on short-day photoperiods. The results are discussed in terms of a possible extra-retinal photoreceptive capacity in neonatal hamsters and with regard to the maturation of the photoperiodic response system known to govern reproductive activity in adult golden hamsters.