Amphetamine-induced dopaminergic hypersensitivity in guinea pigs. Implications in psychosis and human movement disorders.

Following chronic amphetamine pretreatment, guinea pigs demonstrate an increased sensitivity to both d-amphetamine sulfate- and apomorphine hydrochloride-induced stereotyped behavior. This observation suggests that chronic exposure to high doses of a dopamine agonist (d-amphetamine) alters the response of the brain to the subsequent administration of both indirect (d-amphetamine) and direct (apomorphine) dopamine agonists. This altered response may be due to the development of dopamine receptor site hypersensitivity. Clinical evidence suggests that a similar agonist-induced hypersensitivity may play a role in the development of dyskinetic movement disorders and psychoses in humans following the chronic use of such dopamine agonists as amphetamine and levodopa.