Localization of nitric oxide-related substances in the peripheral nervous tissues

Nitric oxide (NO) is now recognized as a transduction molecule in many biological systems, and is known to promote the synthesis of cGMP by activating the soluble guanylate cyclase. NO synthase which fully accounts for all the neuronal activity of NADPH diaphorase catalyzes L-arginine to NO and L-citrulline. In the present study, the localization of NO-related substances, L-arginine, NO synthase, L-citrulline and cGMP in the enteric plexus and dorsal root ganglia was demonstrated with immuno- or enzyme-histochemical methods. L-Arginine was proved accumulated in glial cells, while NO synthase and L-citrulline were found in neurons. Cyclic GMP was predominantly observed in glial cells. These results reveal L-arginine-NO-cGMP pathway may be present in the enteric plexus and dorsal root ganglion as in the brain, and provide visible evidence that NO mediates neuron-glia communications in this pathway.