GUal activation in spinal cord in a rat model of neuropathic pain

Objective To investigate the response of astrocytes in lumbar spinal cord in a rat model of chronic constrictive injury (CCI).Methods Forty-eight male SD rats weighing 220-280 g were randomly divided into 2 groups (n=24 each):groupⅠCCI and groupⅡsham operation.CCI was produced by placing 4 loose ligatures on the right sciatic nerve at 1 mm intervals with 4-0 chromic catgut.The threshold to von Frey filament and to radiant heat stimulation were measured before operation (baseline) and at 1,4,7,14 and 28 d after operation.Four animals were killed at each time point and lumbar segment of spinal cord was removed for determination of glial fibrillary acidic protein (GFAP) in the astrocytes in spinal cord by immuno-histochemical assay.Results The threshold to mechanical and thermal stimuli started to decrease at 1 d after operation (CCI). Mechanical and thermal hyperalgesia peaked at 7 d and 4 d after operation respectively and persisted until the end of experiment.Immuno-histechemical assay demonstrated that GFAP positive astrocytes in the dorsal horn on the operated side significantly increased at 4 d after operation and reached the peak at 7 d and was maintained at a high level until the end of experiment.Conclusion Ghal activation is involved in the mechanism of neuropathic pain.