COPULATION ACTIVATES FOS-LIKE IMMUNOREACTIVITY IN THE MALE QUAIL FOREBRAIN

It has been demonstrated using Fos immunocytochemistry that copulation activates specific cell populations in the mammalian brain. Prior to this study, no similar work has been carried out in birds. In mammals, Fos has identified brain circuits activated by genital (penile)/somat osensory and by olfactory/vomeronasal stimuli. Such inputs, of course, should play little or no role in birds (no penis, little or no role f or olfaction) and a differential responsiveness could therefore be exp ected. Male Japanese quail (Coturnix japonica) were allowed to interac t freely with adult females and the presence of active sexual behavior , including cloacal contact movements, was confirmed in each case. Con trol subjects were exposed to a domestic chick (same size as an adult quail) and no sexual behavior was observed. Copulation induced the app earance of Fos-like immunoreactive (FLI) cells in the preoptic area, t he hyperstriatum ventrale, parts of the archistriatum, and the nucleus intercollicularis. Induction of FLI cells was observed throughout the rostral to caudal extent of the preoptic region of males from the lev el of the tractus septomesencephalicus to the level of the anterior co mmissure, and in the rostral part of the hypothalamus to the level of the supraoptic decussation. The FLI cells did not lie directly adjacen t to the third ventricle, but were located 500-1000 mu m from the vent ricle wall at the level of the lateral edge of the medial preoptic nuc leus or, in more caudal sections, in a position ventrolateral to the b ed nucleus striae terminalis. It is unlikely that the Fos induction in males resulted from copulation-induced endocrine changes because copu lation did not affect plasma levels of luteinizing hormone or testoste rone. It is concluded that the responses were due to copulation-associ ated somatosensory inputs and/or to stimuli originating from the femal e.