Abstract
The effect of early lighting conditions on the sexual development of male and female golden hamsters was investigated, utilizing two experimental paradigms. In the first, hamsters were exposed to one of several daily light cycles (14L:10D,6L:18D,1L:23D, or constant darkness) from birth to 7 weeks 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 is not photoperiodically controlled. In the second experiment, hamsters blinded at birth and exposed for 13 weeks 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 weeks 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. Our results are discussed in terms of a possible extraretinal 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.
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