Expression of Fos-like immunoreactivity in the brain of quail chick emitting the isolation-induced distress calls.

The social isolation intensively induces distress call in neonatal chicks of Japanese quail. The brain regions activated during the isolation were mapped using immunocytochemical detection of c-Fos (the product of immediate early gene c-fos). Fos-like immunoreactivity was observed in a variety of brain regions in isolated chicks that had emitted distress calls. The density of Fos-positive cells in dorso-medial mesencephalic areas (including the intercollicular nucleus and the central gray) was much higher than those of control animals that were kept in groups and emitted very few or no distress calls, whereas the distribution partially overlapped in isolated and control animals. These data, in addition to our lesion and stimulation studies, provide anatomical support for the involvement of the mesencephalic regions in generating distress calls during social isolation.