Lack of the effect of ketamine on some dopaminergic behaviors in rats.

The effects of ketamine on some experimental models for detecting dopaminergic activity were studied in rats. Small doses of ketamine (0.3 and 0.5 mg/kg, ip) induced yawning behavior while higher doses (15 and 30 mg/kg, ip) inhibited both apomorphine- and amphetamine-induced stereotyped behaviors. Ketamine (up to 60 mg/kg, ip) per se failed to elicit typical stereotype or catalepsy similar to that induced by dopamine agonists or antagonists, respectively. Ketamine may have acted as an agonist on dopaminergic autoreceptors. These results do not support the view that the behavioral effects of ketamine are mediated by purely dopaminergic mechanisms.