Deafferentation hypersensitivity in the rat after dorsal rhizotomy: a possible animal model of chronic pain.

Unilateral dorsal rhizotomies were done at the cervicothoracic and lumbosacral spinal cord levels in rats. In preliminary experiments dermatome maps were determined for the roots to be sectioned. The behavior of 37 rats was observed for many months after the rhizotomies. The rats with the dorsal roots sectioned in the cervicothoracic spinal cord exhibited the following behavior: at the border of the skin adjacent to the zone of deafferentation, the rat scratched vigorously and progressively denuded the skin; self-mutilation of varying degrees occurred in the deafferented limb. In some animals scratching occurred in the contralateral skin dermatome opposite to the partially deafferented zone. The rats with the dorsal roots sectioned at the lumbosacral level exhibited hypersensitivity to cutaneous stimulation but there was no scratching or self-mutilation. These results are discussed in the light of previous similar research.