Effects of local illumination of the hypothalamus on spontaneous and flash-induced multiunit activity recorded from the gonadotropic hypothalamic areas in quail.

Multiple unit activity (MUA) was obtained from gonadotropic areas of the hypothalamus in quail. Pellets of radioluminous paint (RLP) were implanted unilaterally either in the nucleus tuberis or in the n. posterior medialis hypothalami. Control data were obtained from birds receiving nonluminous material (RP). Spontaneous MUA was decreased by 25% in gonadotropic arease in RLP-treated quail. Direct permanent photostimulation of hypothalamic neuronal population was not as effective in decreasing MUA as environmental photostimulation (50%). Activation in firing rates, which was constant in nonphotostimulated intact birds in response to repetitive flash-light stimulations, was completely suppressed after implantation of RLP.