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 nitric oxide synthesis in the spinal nerve L5 lesion model for neuropathic pain in Wistar rats. Seven single fibers with spontaneous activity split from dorsal root L5 showed no response after non-selective blockade of nitric oxide synthesis with NG-nitro-L-arginine methyl ester whereas five were excited after 5-7 min. Three previously silent units were recruited. Blood flow in the dorsal root ganglion decreased. None of fifteen axotomized afferents tested responded to selective blockade of neuronal nitric oxide synthesis with 7-nitroindazole. It is concluded that neuronal nitric oxide is not involved in the generation of spontaneous activity in axotomized afferent neurons in this model. We suggest that the vasoconstriction induced by blockade of endothelial nitric oxide may be responsible for the excitatory responses. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.