Hamstei testes which have undergone short photoperiod-induced atrophy become refractory to the effects of short photoperiod after spontaneous or light-induced recrudescence (Reiter, 1974). We have termed this phenomenon, “scotorefractoriness.” The present experiments assessed relations between photoperiod-induced testicular regression, recrudescence and scotorefractoriness. Experiment 1 established that mere testicular regression was not sufficient to induce scotorefractoriness. Testes of some animals which were regressed by 6 or 9 weeks of exposure to a LD 2:22 photoperiod (short days) and recrudesced by 9 weeks of exposure to a LD 14:10 photoperiod (long days) subsequently regressed again in response to a second 9 week exposure to LD 2:22; others appeared scotorefractory. Experiment 2 determined that animals which achieved complete testicular regression during 9 weeks of LD 2:22 were less sensitive to the stimulating effects of long days than were animals which were in LD 2:22 for 12–15 weeks. The transition from long to short days initiates gonadal atrophy, permits subsequent testicular recrudescence and also induces scotorefractoriness. Short day exposure initially decreases the sensitivity of the neuroendocrinetesticular axis to the effects of long days; the subsequent recovery of sensitivity to photostimulation may parallel processes involved in spontaneous testicular recrudescence.
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Irving H. Zucker (1977) studied this question.