DOPAMINE-RECEPTOR ANTAGONISTS FAIL TO PREVENT INDUCTION OF COCAINE SENSITIZATION

We investigated the ability of dopamine D-1 and D-2 class receptor ant agonists to prevent the induction of behavioral sensitization to cocai ne. The D-2 receptor antagonist eticlopride failed to prevent the indu ction of cocaine sensitization. An intermediate dose of the D-1 recept or antagonist SCH 23390 (0.1 mg/kg) appeared to prevent the induction of cocaine sensitization when tested after 3 days of withdrawal, but s ensitization was clearly evident after 10 days of withdrawal. High dos es of SCH 23390 alone produced supersensitivity to the behavioral effe cts of cocaine and to the inhibitory effects of D-1 receptor agonists on nucleus accumbens neurons. Co-administration of eticlopride and SCH 23390 also failed to prevent the induction of cocaine sensitization. SCH 23390, but not eticlopride, prevented the expression of cocaine se nsitization. We conclude that dopamine receptors are either not involv ed in the induction of cocaine sensitization or that redundant mechani sms exist to produce the same neuroadaptations. (C) 1998 American Coll ege of Neuropsychopharmacology. Published by Elsevier Science Inc.