Nitric oxide modulates responses to sensory nerve activation of the perfused rat mesentery

The modulatory actions of nitric oxide on sensory nerves were investigated on dilator responses of the perfused rat mesentery to transmural nerve stimulation. N omega-nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide synthesis, caused a significant augmentation of vasodilator responses to transmural nerve stimulation, an effect which was abolished by L-arginine. L-NAME had no effect on vasodilator responses to exogenous calcitonin gene-related peptide. In preparations without endothelium L-NAME still caused potentiation of vasodilator responses to transmural nerve stimulation. Methylene blue, an inhibitor of guanylate cyclase, also significantly enhanced vasodilator responses to transmural nerve stimulation. After pretreatment with diethyldithiocarbamate to inhibit superoxide dismutase, vasodilator responses to transmural nerve stimulation were also potentiated. This response was abolished by exogenous superoxide dismutase. These findings suggest that endogenous nitric oxide modulates, in an inhibitory fashion, the actions of sensory nerves in the rat mesentery. The results also suggest that endogenous superoxide dismutase may participate in the regulation of the actions of sensory nerves via control of cellular superoxide anion level.