Fig. 4. Time course of antinociceptive effects (percentage maximum possible effect) for various mixtures of 30 or 100 μg racemic ketamine, R (−)-ketamine, or S (+)-ketamine with dexmedetomidine. Each point represents the mean ± SEM of the data from 5–14 animals. *P < 0.05 versus baseline; +P < 0.05 versus saline; x P < 0.05 versus racemic ketamine–dexmedetomidine treatment.