Sites and action spectra for encephalic photoreception in the Japanese quail.

Sexually mature Japanese quail, Coturnix coturnix japonica, were transferred to short environmental photoperiod for 20 days, during which they received encephalic illumination via surgically implanted optic fibers. White light delivered to discrete sites in the basal hypothalamus induced photogonadal response for testicular maintenance. There was also a strong positive response to monochromatic red, green, or blue light delivered to these areas, and this response was of equal magnitude regardless of wavelength. Illumination of sites in the median eminence and pars nervosa was also effective in inducing photogonadal response. White light delivered to the optic chiasma was effective, whereas green or blue light to this structure had no effect. Illumination of the preoptic hypothalamus or the dorsal cortex was also without effect. Our data indicate that there are photoreceptive sites in and near the basal hypothalamus that, when illuminated directly, are capable of responding to a broad range of visible wavelengths.