Glutathione (GSH), an inhibitor of nSMase, prevented the acute hyperalgesia induced by NGF. (A) GSH (1.8 µmoles/paw total dose), when pre-injected (120 mM, 10 µL) 15 min before and then co-injected (60 mM, 10 µL) with NGF (500 ng/10 µL), prevented hyperalgesia measured at 1–1.5h, but did not that measured on the next day (n=8). *P<0.05 vs. baseline IPSI (Friedman test followed by Dunn's post hoc test). (B) When glutathione (1.8 µmoles/ paw total dose) was injected (120 mM, 10 µL) s.c. intraplantar 1.5h before and then co-injected (60 mM, 10 µL) with NGF (500 ng/10 µl) the acute stage of hyperalgesia still occurred (n=4, p=0.0324 for both 4g and 15g forces (Friedman test); #P<0.05 compared to the CLP responses (two-tailed Mann-Whitney test)