RESPONSES OF AXOTOMIZED AFFERENTS TO BLOCKADE OF NITRIC-OXIDE SYNTHESIS AFTER SPINAL NERVE LESION IN THE RAT

Lesioned afferents were tested for their responses to blockade of nitr ic oxide synthesis in the spinal nerve L5 lesion model for neuropathic pain in Wistar rats. Seven single fibers with spontaneous activity sp lit from dorsal root L5 showed no response after non-selective blockad e of nitric oxide synthesis with NG-nitro-L-arginine methyl ester wher eas five were excited after 5-7 min. Three previously silent units wer e recruited. Blood flow in the dorsal root ganglion decreased. None of fifteen axotomized afferents tested responded to selective blockade o f neuronal nitric oxide synthesis with 7-nitroindazole. It is conclude d that neuronal nitric oxide is not involved in the generation of spon taneous activity in axotomized afferent neurons in this model. We sugg est that the vasoconstriction induced by blockade of endothelial nitri c oxide may be responsible for the excitatory responses. (C) 1998 Else vier Science Ireland Ltd. All rights reserved.