Abstract
Relationships between photoperiodically controlled testicular responses and the amount of neurosecretory materials in the anterior median eminence of Japanese quails have been investigated. Birds reared under 8-hour daily photoperiods from hatch to 25 days of age had a smaller amount of neurosecretory materials in the median eminence than those reared under continuous light. At 25 days of age testes showed much growth in most birds under continuous light, but less under 8-hour photoperiods. There was a correlation between testicular weight and the amount of neurosecretory materials accumulated in the median eminence. After shortening the photoperiod from continuous light to 8 hrs. per day at 43 days of age, the neurosecretory material in the median eminence had increased remarkably by 48 days of age. Alteration of light period was accompanied by testicular involution. This suggests that the release of neurosecretory materials from the median eminence was restrained by the shortened daily photoperiods. A hypothetical role of the neurosecretory material accumulated in the median eminence in the testicular development of Japanese quails is discussed.
