Study of astrocytes and synaptic remodeling in the rat spinal cord after chronic constriction injury of sciatic nerve

Objective To study the changes of astrocytes and synaptic remodeling in the rat spinal cord after chronic constriction injury (CCI) of sciatic nerve.Methods 12 female SD rats weighing 180～250 mg were divided randomly into 2 groups with 6 animals each.Group model:The right sciatic nerve was exposed and four ligatures (4-0 chromic gut) were tied loosely around it,with an interval of 1.0 mm between each.Then chronic constriction injury model was established.Group control:Identical surgery,except that the ligatures were not applied,was performed as a sham-operative control.Mechanical withdrawal thresholds were measured before the constriction injury and on post-CCI days 7 and 14.The changes of astrocytes and synaptophysin of the spinal cord in post-surgery days 14 were detected quantitatively with immunohistochemistry and computerized image analysis.Results Pain threshold in group model reduced significantly compared with that in group control (P 0.05) and the established mechanical allodynia in Group model was maintained for ten days.The density of synaptophysin immunoreactivity in the superficial dorsal horn as compared with that in control group was remarkably increased by 66.9% on the 14th day after CCI (P 0.01).The GFAP-positivity in group CCI model was significantly increased by 44.2% compared with that of control group rats (P 0.01).Conclusions CCI caused an increase of astrocytes and synaptophysin immunoreactivity in the superficial layers of the dorsal horn,and this might result in the development of neuropathic pain.