RESUMEN
Objective To investigate the changes in the expression of connexin 43 ( Cx43) in astrocytes in the spinal dorsal horn in a rat model of chronic neuropathic pain. Methods Twenty male SD rats weighing 200-250 g were randomly divided into 2 groups : (A) chronic constriction injury group (CCI) received 4 loose ligatures placed on the right sciatic nerve according to Xie[5] (n = 10) and (B) sham operation group in which the right sciatic nerve was exprosed but not ligated ( n = 10) . The pain behavior was evaluated and the paw withdrawal thermal latency (PWTL) and paw withdrawal electric threshold (PWET) were measured the day before operation (D0 baseline) and on the 1st, 3rd, 5th, 7th and 14th day after operation (T1 , T3, T5, T7, T14 ) . On the 14th postoperative day the animals were sacrificed and the L4-5 segment of spinal cord was removed for detection of the expression of Cx43 and glial fibrillary acid protein ( GFAP) in the spinal dorsal horn by immuno-histochemistry. Results In CCI group the rats displayed pain behavior after operation and only 2 of them recovered normal behavior on D14 and their PWTL was shortened and PWET lowered after operation compared to the baseline values (D0), while in the sham operation group PWTL and PWET returned to the baseline after D7. The GFAP positively stained area was significantly larger in the right spinal dorsal horn in CCI group (29?7% ) than in sham operation group (19?5% ). The Cx43 positively stained area was 17?3% in CCI group and 4?1 % in sham operation group. Conclusion Cx43 and GFAP expression increase in the astrocytes in the spinal dorsal hom of the affected side in rats with chronic neuropathic pain, suggesting that the astrocytic gap junction may play an important role in chronic neuropathic pain.