Effects of Short Photoperiod on Pituitary and Testicular Function in the Chinese Hamster, Cricetulus griseus1

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Abstract
Adult male Chinese hamsters (Cricetulus griseus) were transferred from a long photoperiod (14L:10D) to a short photoperiod (5L:19D). After 6 weeks, the weights of the testes and the seminal vesicles as well as the concentration of androgens (testosterone plus dihydrotestosterone) in the testes were significantly lower in animals exposed to a short photoperiod than in age-matched long-photoperiod controls. The decline in testicular weight and activity was followed by a spontaneous recovery, and after 19 weeks there were no significant differences in the weights of the testes or the seminal vesicles between the animals exposed to long and short photoperiod. Throughout this study, photoperiod had no significant effects on plasma levels of gonadotropins or Prl. The time course of changes in testicular and seminal vesicle weights in animals transferred to short photoperiod was similar to those described in the golden hamster and other seasonally-breeding species of rodents. However, the magnitude of these responses was much smaller in C. griseus than in other species.