Fig. 6. Effect of A7 administered naloxone and muscimol on N2O-induced antinociception. The plantar test for withdrawal latency was assessed when saline (0.2 μl × 2), naloxone (0.25 μg/0.2 μl × 2), or muscimol (0.5 μg/0.2 μl × 2) was microinjected into the A7, which was followed by 30 min of exposure to either air or N2O (75%)–O2(25%). The latency is expressed as the percentage of the maximum possible effect. Bar = the mean number for four animals; error bar = the SD. *P < 0.05 versus saline–air group. #P < 0.05 versus saline–N2O group.