Figure 2.

Effects of i.m. administration of APETx2 on mechanical hypersensitivity in the acid-induced muscle pain model. Acidic saline (pH 4, 100 µL) was injected into the gastrocnemius muscle of the rat twice, 5 days apart. APETx2 was administered prior to the second injection of acid saline. Mechanical hypersensitivity was assessed by measuring withdrawal thresholds to von Frey filament stimulation for the ipsilateral (A, C) and contralateral (B) hind paws. Data are expressed as mean ± SEM. Change in threshold relative to pretreatment levels was calculated and plotted as a function of the dose of APETx2 (C). APETx2 was also applied after second i.m. injection of acid saline (D). *P < 0.05 versus vehicle group.