[The testicular response to selective photostimulation of the basal hypothalamus or of the preoptic area of the quail].

Radioluminous paint (R.L.P.), 0.029 cd/m2, was implanted in various parts of the hypothalamicpreoptic system. Small pellets, 0.6 mm in diameter, 0.2 mm thick, were stereotaxically located either in the basal medial hypothalamus or in the suprachiasmatic-preoptic area. Basal hypothalamic illumination through R.L.P. resulted in a strong testicular growth. No testis enlargement was induced after anterior implant or R.L.P. Results are discussed in terms of hypothalamic deep photoreceptors and of functional roles devoted to basal hypothalamic and preoptic regions with respect to the photosexual reflex.