Effect of gabapentin on activation of glial cells in spinal cord after chronic constrictive injury to sciatic nerve in rats

Objective To investigate the effect of gabapentin on the activation of glial cells in the spinal cord after chronic constrictive injury (CCI) to sciatic nerve in rats.Methods Twenty-four male SD rats weighing 180-220 g were randomly divided into 3 groups (n = 8 each): group Ⅰ sham operation (group S), group Ⅱ CCI and group Ⅲ gabapentin + CCI. Right sciatic nerve was exposed and 4 loose ligatures were placed with 6-0chromic catgut. Seven days after operation gabapentin 50 mg/kg in 5 ml was given by intragastric gavage twice a day for 5 days in group Ⅲ. Paw withdrawal threshold to mechanical stimulation with von Frey filaments was measured one day before (baseline) and at 7, 15 d after operation. The animals were killed at 15 d after operation. The lumbar segment L4-5 of the spinal cord was removed. Immunohistochemical double mark technique was used to detect the activation of astrocytes and microglias in the spinal cord. Results Paw withdrawal threshold to mechanical stimulation was significantly decreased on the 7th and 15th day after CCI operation in group CCI as compared with group S. After 5 day treatment with gabapentin, the withdrawal threshold to von Frey hair stimulation was significantly higher in group Ⅲ than in group Ⅱ . The activation of astrocytes and microglias in the spinal cord was significantly enhanced in group CCI as compared with group S. Treatment with gabapentin significantly inhibited CCI-induced activation of astrocytes and microglias in the spinal cord. ConclusionGabapentin reduces neuropathic pain by inhibiting activation of glial cells in the spinal cord. Key words: Cyclohexanecarboxylic acids;  Astrocytes;  Microglia;  Neuralgia;  Spinal cord