Stereospecific blockade of N-methyl-D-aspartate transmission by MK 801 prevents priming of SKF 38393-induced turning.

In rats unilaterally lesioned with 6-hydroxydopamine, the D-1 agonist SKF 38393 (3 mg/kg SC) induced contralateral turning only after priming with a dopaminergic agonist such as apomorphine. Administration of the N-methyl-D-aspartate receptor antagonist (+) MK 801 (0.1 mg/kg IP) 15 min before apomorphine (0.1 mg/kg SC) prevented the ability of apomorphine to act as a primer while potentiating its acute contralateral turning effects. The inactive isomer (-) MK 801 was without effect. The results indicate that the N-methyl-D-aspartate receptor exerts a permissive role on priming.