Spinalization increases the mechanical stimulation-induced withdrawal reflex threshold after a sciatic cut in the rat.

The purpose of the present study was to establish whether supraspinal structures modulate mechanical 'adjacent hyperalgesia'. After a chronic sciatic cut, the paw withdrawal threshold to mechanical stimulation was lower, and the latency of noxious radiant heat-induced withdrawal reflex was shorter at the traumatized side than at the intact side. Then the rats were spinalized, and the withdrawal threshold to mechanical stimulus increased at the injured side, but the withdrawal latency induced by noxious heat decreased at the intact side. No side differences between the injured and the intact side could be detected after spinalization. Thus supraspinal structures may participate in maintenance of mechanically evoked paw withdrawal reflex after a sciatic injury.