Cholinergic modulation of separation distress in the domestic chick.

The effects of nicotine, carbachol, hexamethonium and scopolamine were investigated on distress vocalizations (DBs) of acutely isolated domestic chicks. Nicotine attenuated, while the antimuscarinic scopolamine increased the frequency of separation-induced DVs. Furthermore, the stress attenuating effects of nicotine were blocked by pretreatment with scopolamine. These results implicate muscarinic receptor participation in the control of separation-induced distress, and support the suggestion that nicotine-induced DV suppression may result from activation of behaviorally relevant muscarinic receptors via central release of acetylcholine.