Crossed-withdrawal reflex in a rat model of neuropathic pain: implications in neural plasticity.

Recently we developed a neuropathic rat model employing a distal sciatic nerve branch injury, in which rats show vigorous behavioral signs of neuropathic pain. This study was performed to evaluate the crossed-withdrawal reflex in which any stimuli applied to the uninjured side produces allodynic signs on the injured side in our neuropathic pain model. Rats that received neuropathic surgery developed behavioral signs of neuropathic pain. In addition, these rats developed pain responses of the injured paw to stimuli applied to the contralateral uninjured paw, therefore, demonstrating 'the crossed-withdrawal reflex.' Moreover, electrical stimulation of the uninjured paw developed evoked potentials in the ventral root on the injured side. These results suggest that information processing from input on the uninjured side to output on the injured side, can be facilitated in rats with a nerve injury and that neuroplasticity may contribute to the crossed-withdrawal reflex.