Mechanical hyperalgesia induced after Pinch nerve injury. Time course of mechanical pain withdrawal threshold measured by the von Frey filaments after unilateral Pinch (n=5). Ipsilateral hind paw displays a strongly painful behavior measured by pain withdrawal threshold compared with sham group animals (n=5); This mechanical hyperalgesia is not seen in the contralateral paw compared with sham group animals (n=5). Data are expressed as mean±S.EM. *, P <0.05 compared with the sham group.