Fig. 1. Buprenorphine increased paw withdrawal latency (PWL) after thermal stimulus. The ordinate shows PWL expressed as percent maximum possible effect (% MPE). The abscissa shows time course of % MPE relative to injection at time zero. Asterisks (*) indicate a significant increase in % MPE after intravenous administration of buprenorphine (1 mg/kg) compared with saline (vehicle control).