The effects of alpha-adrenergic blocking agents on stereotyped behavior induced by apomorphine in rats were studied. 2. Pretreatment of rats with 5 and 10 mg/kg of phenoxybenzamine or phentolamine displaced the dose-response curves for apomorphine-induced stereotypy to the left in a dose dependent manner. The ED50 for apomorphine was reduced from 1.92 +/- 0.38 (mean +/- SEM) to 0.63 +/- 0.08 by 10 mg/kg phenoxybenzamine and from 1.92 +/- 0.38 to 0.61 +/- 0.10 by 10 mg/kg phentolamine. 3. These results support the view that the expression of dopaminergic-induced stereotyped behavior is dependent on noradrenergic activity in the central nervous system.
