The effect of pre-emptive intrathecal administration of L-NAME on c-fos expression in rats spinal cord induced by neuropathic pain / 中华麻醉学杂志

ABSTRACT

Objective To investigate the effect of intrathecal (IT) administration of L-NAME , a nonselective nitric oxide synthase (NOS) inhibitor, on c-fos expression in spinal cord induced by neuropathic pain. Methods Eighty-four female SD rats weighing 220-310g, which showed no signs of never injury 3 to 4 days after IT catheterization with the tip of catheter reaching the lumbar region, were divided into 4 groups at random group A received IT 0.9% NaCl 10?g 15min before sham operation ( n = 16); group B received IT 0.9% NaCl 10?l 15min before ligation of sciatic nerve ( n =24); group C received IT L-NAME 10?l (250?g) 15min before sham operation ( n = 16); group D received IT L-NAME 10?l (250?g) 15min before ligation of sciatic nerve (n =24) . The animal in each group were further divided into 4 subgroups ( n = 4-6) and sacrificed on 1st, 3rd, 7th and 14th day after operation. In addition 4 rats which had received no operation of any kind were sacrificed and served as control. The c-fos expression in ipsilateral dorsal horn of spinal cord was detected by immunohistochemistry technique. Results In normal rats in control group (no IT catheterization, no operation) there were only a few fos-positive neurone (3.4? 0.9). The c-fos expression in the ipsilateral dorsal horn of spinal cord greatly increased both in group A and B. In group B there were more fos-positive neurons (FLIN) in the ipsilateral dorsal horn on the 3rd, 7th and 14th day as compare with group A. With pre-emptive intrathecal administration of L-NAME, the increase in ipsilateral c-fos expression induced by ligation of sciatic nerve was inhibited. In group D the number of fos-positive neurons in ipsilateral dorsal horn decreased by 53.8%, 57.1% and 43.2% on the 3rd, 7th and 14th day after operation as compare with group B. On the 1st day afteroperation there was no difference-in FLIN in the ipsilateral dorsal horn between group B and D. Conclusion Nitric oxide plays an important role in mediating the neuropathic pain which can be effectively attenuated or prevented by pre-emptive IT administration of L-NAME.