Direct dopamine agonist-like activity conditioned to cocaine.

Rats were lesioned unilaterally by infusions of 6-hydroxydopamine aimed at substantia nigra. In subsequent behavioral testing, apomorphine treatment resulted in rotation (circling) directed contralaterally with respect to the lesion and cocaine treatment induced ipsilaterally directed rotation. When 0.05 mg/kg apomorphine and 10 mg/kg cocaine were administered simultaneously, rotation appropriate for apomorphine resulted. After a number of paired administrations, treatment with cocaine alone resulted in apomorphine-like rotation.