Figure 3. Reduction in hind paw withdrawal latency for 180 min (mean values +/− SD, six animals per group) after pentobarbital injection for L-NAME- and 7-NI-treated groups (n = 6 animals per group). L-NAME (F = 27.7, P < 0.001, one-way analysis of variance) and 7-NI (F = 25.3, P < 0.001) administered before pentobarbital blocked nocifensive reflex facilitation in a dose-dependent manner. The saline/saline group received no pentobarbital. All other groups were injected (intraperitoneally) with saline (saline/pentobarbital), L-NAME (2.5, 10, 25, 50 mg/kg) or L-NAME, 25 mg/kg, + L-arginine, 300 mg/kg) or 7-NI (5 or 50 mg/kg) 30 min before the pentobarbital injection. *Significantly different from saline/pentobarbital controls (P < 0.05).