Effect of MK-912 on the duration of anesthesia induced by the combination of xylazine (10 mg/kg) and ketamine (80 mg/kg) in C57BL/6 mice. Fifteen minutes after the induction of anesthesia, mice were injected with increasing doses of MK-912 (n = 5 per dose) or vehicle (PEG 60%; n = 34). The duration of anesthesia was assessed by the return of the righting reflex. Results are expressed as mean ± SEM. *Significantly different from vehicle group at P < 0.05.