Changes of nitric oxide synthase activity in response to different levels of social separation in two day old domestic chicks (Gallus gallus domesticus)

An increase of nitric oxide synthase (NOS) activity was found in the brain of few day old chicks after exposure to different social stress situations. The cerebellum, which showed the highest NOS activity, displayed the most sensitive response. Increases of NOS activity were found in the chronically separated tall regions) and in the acutely separated animals (cerebellum). In the cerebellum and the midbrain/brainstem/tectum NOS activity was signi ficantly different also between the chronically separated and chronically i solated groups. NOS activity was higher in the cerebellum of the acutely se parated group compared to the chronically isolated and social controls, a s imilar trend was found in the midbrain/brainstem/tectum sample, the values in the forebrain remained unchanged. Chronic isolation did not induce signi ficant changes of NOS activity. These data confirm that the newborn chick i s a suitable model for the experimental investigation of stress-induced alt erations of brain maturation and behavioural development.