Cold exposure enhances tactile allodynia transiently in mononeuropathic rats

A laser and erythrosin-B-induced sciatic nerve injury decreases thresholds of a mechanically induced paw withdrawal reflex and enhances cold-induced w ithdrawal behavior of the affected limb. Exposure of the affected paw to a normally innocuous cold stimulus results in a transient decrease in the thr eshold of the mechanically evoked paw withdrawal reflex in neuropathic but not in intact rats. The present data suggest that in an experimental neurop athic state a normally innocuous cold stimulus may further sensitize spinal ly mediated withdrawal reflexes to stimuli of another stimulus modality in this case, to innocuous tactile stimuli. Therefore, testing mechanical allo dynia in neuropathic rats immediately after testing cold allodynia may prod uce artifactual results. (C) 2000 Academic Press.