Treatments of neuropathic pain were included Ca blocker, steroid medication, epidural or spinal local anesthetics, intravenous reserpine and phenoxybenzamine and operative sympathectomy. This study was performed to evaluation the effects of laser radiation and intraperitoneal guanethidine to the neuropathic pain.

The neuropathic pain were produced by the tight ligation of L5 and L6 spinal nerves in the adult rats (Sprague-Dawley) withdrawl response to the non-noxious stimulation(mechanical allodynia) were increased and response to the cold stimulation (cold allodynia) were increased too. After that, we injected 50 mg/kg guanethidine intraperitoneally and radiated the He-Ne laser to the operated site to evaluate the effect of chemical sympathectomy and laser radiation.

Mechanical allodynia was significantly reduced(p<0.05) 1st and 2nd day after chemical sympathectomy. Cold allodynia was significantly reduced(p<0.05) 1st day after chemical sympathectomy. Mechanical and cold allodynia were not significantly reduced after laser radiation.

It was suggested that the chemical sympathectomy via intraperitoneal injection of guanethidine 50 mg/kg had the therapeutic effect of neuropathic pain in the surgically operated rat which was ligated L5, 6 spinal nerve.