EFFECT OF DIFFERENT PHOTOPERIODS AND BLINDING ON OVARIAN AND TESTICULAR FUNCTIONS IN NORMAL AND TESTOSTERONE-TREATED RATS

Postnatal administration of testosterone propionate (1 mg; s.c.) renders the rat gonadotropic functions more light-dependent than in untreated controls. In the female, a normal follicular development and the persistence of vaginal estrus are only possible when the animals are exposed to light. In the male, light deprivation causes tubular and interstitial atrophy. The difference in testicular weight and structure between animals kept in the dark or exposed to light is strikingly amplified by postnatal testosterone treatment. This increased light sensitivity of reproductive functions, which affects sex accessories and the pituitary as well, may be accounted for by the effect of testosterone sterilization upon steroid feedback thresholds. Exposure of blinded, testosterone-treated animals to light brings about a slight, but consistent, increase in gonadotropin release. In some instances, this effect is at the limit of statistical significance. Although these results do not permit formal conclusions as to the importance of nonretinal photosensitive structures for gonado-stimulating mechanisms in the rat, they indicate that the problem deserves additional consideration. © 1968.