Behavioral supersensitivity to apomorphine and amphetamine after chronic high dose haloperidol treatment.

Rats administered chronic haloperidol (5 mg/cc) for 2 months exhibited stereotyped gnawing during chronic haloperidol treatment, and after withdrawal from haloperidol, showed significantly greater stereotyped behavior induced by apomorphine or L-amphetamine compared to saline controls. Chronic administration of benztropine mesylate concomitantly with haloperidol reduced the effects of chronic haloperidol on drug induced stereotyped behavior during the withdrawal period.