Fig. 3. (A ) The effect of acute administration of MK-801 (10–200 μg/kg) on the sleep time induced by acute administration of dexmedetomidine (Dex; 100 μg/kg intraperitoneally). * P < 0.05 different from saline, n = 6. (B ) Acute administration of MK-801 did not block dexmedetomidine-induced tolerance to the hypnotic effect of dexmedetomidine. * P < 0.05 different from control saline, n = 6–7. (C ) Chronic administration of MK-801 did not affect the sleep time induced by acute administration of dexmedetomidine (100 μg/kg intraperitoneally). (D ) Coadministration of MK-801 (4 and 16 μg · kg−1· h−1) blocked tolerance to the hypnotic effects of a challenge dose of dexmedetomidine (100 μg/kg intraperitoneally). * P < 0.05 different from control, N = 6–8. All values are mean ± standard error of 7–8 rats. LORR = loss of righting reflex.
