Alteration of brain nicotinic receptors induced by immobilization stress and nicotine in rats.

Immobilization stress (2 h.day-1, for 2 weeks) caused downregulation of the nicotinic receptors ([3H]cytisine binding sites) in the rat brain (cerebral cortex and midbrain). However, chronic nicotine treatment abrogated stress induced downregulation of the [3H]cytisine binding sites, suggesting that chronic nicotine treatment may block stress activated nicotinic receptor-mediated neurotransmission.