The Effect Of Continuous Peripheral Nerve Blockage By Local Anesthetics On The Expression Of GAP-43 In The Dorsal Root Ganglion During The Development Of Neuropathic Pain

ObjectiveBy using immunohistochemistry method, we observed the effect of continuous peripheralnerve block by local anesthetics on growth associated protein-43(GAP-43) expression during thedevelopment of neuropathic pain.MethodsThirty-five SD rats were randomly divided into four groups: control group; simple sciaticnerve section(axotomy) group; peripheral nerve block before section group; peripheral nerveblock after section group. Each group was subdivided equally into 2 groups according to thedifferent postoperative interval: 3 and 7 days. The fight sciatic nerve were exposed andtransected at 1cm distal to sciatic notch. The peripheral nerve block groups were injected withlocal anesthetics 1 hour before or 4 hours after operation respectively. At various interval altersurgery, the dorsal root ganglions to the transected sciatic nerve were harvested. Immunohisto-chemistry and image analysis were used to evaluate the expression of GAP-43.ResultsAt the third and seventh day after surgery, the GAP-43 expression in the simple sciaticnerve section group was higher than that in control group; while both in peripheral nerve blockbefore and after surgery groups the expression of GAP-43 had no different from that in control group. The study suggests that continuous peripheral nerve block 1 hour before or 4 hours aftersurgery can suppress the high expression of GAP-43 during the development of neuropathiepain.Conclusions1. GAP-43, which regulates the regeneration and recombination of axons after nerve injury, isthe molecule marker of neuronal plasticity and plays an important role in the induction oflong-term potentiation(LTP). We found the high expression of GAP-43 in the mouse sciaticnerve transection model of neuropathic pain, which suggests that the GAP-43 involve in thedevelopment of neuropathic pain.2. Continuous blockage of peripheral nerve during the development of neuropathic pain,suppressing the transmission of nociceptive stimulus and ectopic activity, could reverse thehigh expression of GAP-43 and keep it in a normal level. It suggests that the ectopic activityin axotomized afferent neurons might be the positive signal of GAP-43 expression.3. Both in peripheral nerve block before and after siatic nerve transection groups the expressionof GAP-43 had no different from that in control group. Comparing to the nociceptivestimulus of nerve transection, the ectopic activity arising in lesioned afferent neurons is muchmore important to stimulate the high expression of GAP-43.