Fig. 2. Effects of intrathecal administration of hemicholinium-3 (HC-3; 1 μg, n = 6), ethylcholine mustard aziridinium ion (AF64A; 5 nm, n = 7), or its vehicle (n = 6) on the analgesic effect of intravenous injection of 2.5 mg/kg morphine in rats. Data presented as mean ± SEM. *P < 0.05 versus  respective baseline control. **P < 0.05 versus  vehicle-treated group.