Change in activity of NF-κB in astrocytes in spinal dorsal horn in a rat model of neuropathic pain

Objective To investigate the change in NF-κB activity in astrocytes in spinal dorsal horn in a rat model of neuropathic pain and the underlying mechanism. Methods Sixteen male SD rats aged 2-3 months weighing 220-280 g were randomly divided into 2 groups ( n = 8 each) : sham operation group (group S) and CCI group. Neuropathic pain was induced by chronic constrictive injury (CCI) . Right sciatic nerve was exposed and 4 loose ligatures were placed on the sciatic nerve at 1 mm intervals with 4-0 chromic catgut. In group S the right sciatic nerve was exposed but not ligated. The paw withdrawal threshold (PWT) to von Frey filament stimulation and paw withdrawal latency (PWL) to radiant heat stimulation were measured at 1 d before (baseline) and 7 d after operation. The animals were then killed and the lumbar segment of the spinal cord (L_(4-6)) was removed. The expression of NF-κB in the astrocytes in spinal dorsal horn was determined by immuno-histochemistry. Results PWT and PWL to mechanical and thermal stimuli were significantly decreased after operation as compared with the baseline before operation in group CCI. The number of NF-κBp65 immunoreaction positive cells in the spinal dorsal horn on the operated side was significantly larger in group CCI than in group S. Conclusion NF-κB signal transduction pathway in the astrocytes in the spinal dorsal hom may be involved in neuropathic pain. Key words: NF-kappa B; Neuralgia; Spinal cord; Astrocytes