Fig. 2. The sedative effect of dexmedetomidine (Dex; 150 μg/kg intraperitoneally) in drug-naïve rats was not decreased by preincubation of a concentrated solution (6 mg/ml) with MK-801 (4.8 mg/ml) or NO²-arginine (2.5 mg/ml) at 37°C for 14 days. The final concentrations of MK-801 and NO²-arginine were 120 μg/kg and 63 μg/kg, respectively. * P > 0.05. All values are mean ± standard error of 6–7 rats.