The involvement of the preoptic-suprachiasmatic region in the photosexual reflex in quail: Effects of selective lesions and photic stimulation.

Small bilateral lesions of the preoptic and anterior hypothalamic regions completely suppressed the light-induced testicular growth in quail. Photic stimulation was selectively applied to this region using a small pellet of radioluminous paint (RLP). This local photostimulation induced no testicular growth in short day quail. On the contrary, testes were markedly enlarged after RLP was implanted in the tuberal or in the dorsal area of the infundibular complex of short day quail. This response was as large as in controls reared under 18L-6D. It is therefore confirmed that neuronal populations located in the infundibular complex are directly photosensible. No direct photosensitivity was observed in the preoptic and anterior hypothalamic regions and it is suggested that these areas can serve as a relay for retinal information.