One trial conditioning with apomorphine is blocked by cycloheximide

Rats with unilateral 6-hydroxydopamine lesions of substantia nigra were treated with 0.05 mg/kg apomorphine and observation of their circling behavior was made. Twenty minutes after the apomorphine treatment they were injected with saline or 2 mg/kg cycloheximide. Two weeks after drug treatment, control animals exhibited rapid contralateral rotation in response to being placed in the rotation environment. This conditioned rotation was not observed in cycloheximide-treated animals. After the first test trial animals received a second apomorphine administration, this time followed by saline injection in both groups. Subsequent to the second apomorphine treatment both groups showed conditioned rotation.