Mechanical pain thresholds in animals with early-life (P10) nerve injury (SNI-ipsi) or sham surgery (sham-ipsi) tested in later life (P31), before and after i.p ketamine. SNI surgery animals have lower baseline mechanical pain thresholds but the NMDA antagonist ketamine increases mechanical pain thresholds to normal levels in a dose dependant manner. The clearance of ketamine (72 h post injection) results in the mechanical pain thresholds falling back to pre-ketamine levels. B) The same dose dependent reversal of mechanical hypersensitivity by ketamine is observed when measuring foot paw withdrawal to a von Frey hair. *: (n = 6 per experimental group, 3-way ANOVA, p < 0.001, Tukey, p < 0.05), SNI: spared nerve injury, Ipsi: ipsilateral, Contra: contralateral, ip: intraperitoneal, FPW: frequency of paw withdrawal. Ketamine had no effect upon contralateral (SNI-contra) thresholds or upon sham operated animals.