Dopaminergic and cholinergic influences on motor behavior in chickens.

The dopamine receptor agonist apomorphine enhanced motor activity as measured in stabilimeters and decreased the duration of tonic immobility behavior in chickens in a dose-dependent manner. Haloperidol, a dopamine receptor antagonist, increased the duration of tonic immobility and attenuated the apomorphine-induced increase in activity. Motor activity could also be increased by the cholinergic antagonist scopolamine. In addition, scopolamine was shown to decrease the duration of tonic immobility. On the other hand, the cholinergic agonist pilocarpine increased tonic immobility behavior and decreased scopolamine's effect on motor activity in these birds. Studies of the interaction of dopaminergic and cholinergic systems showed that haloperidol could attenuate the activity-stimulating effects of scopolamine whereas pilocarpine had a similar, but lesser, effect on apomorphine-induced activity. The results support the suggestion that in birds, as in mammals, the dopaminergic and cholinergic systems are intimately involved in the expression of motor behavior.