Extrinsic neural control of nitric oxide synthase expression in the myenteric plexus of rat jejunum

1. The role of extrinsic innervation in the expression of nitric oxide synthase (NOS) in the myenteric plexus remains unknown. In this study, we investigated the effect of extrinsic denervation on NOS expression in rat jejunum. 2. NG-nitro-L-arginine methyl ester (L-NAME)-sensitive non-adrenergic, non-cholinergic (NANC) relaxations induced by transmural nerve stimulation were significantly increased in muscle strips obtained from rats treated with splanchnic ganglionectomy or 6-hydroxydopamine (6-OH-dopamine). Truncal vagotomy or treatment of the coeliac ganglia with capsaicin did not significantly affect NANC relaxations. 3. The number of NOS-immunopositive cells in the myenteric plexus was significantly increased in tissues obtained from rats treated with splanchnic ganglionectomy or 6-OH-dopamine. 4. Western blot analysis and Northern blot analysis showed a significant increase in the density of the immunoreactive NOS band and the NOS mRNA band, respectively, of the tissues obtained from rats treated with splanchnic ganglionectomy or 6-OH-dopamine. 5. Truncal vagotomy or treatment of the coeliac ganglia with capsaicin did not significantly affect the density of NOS band or NOS mRNA band. 6. It is concluded that neuronal NOS expression in the myenteric plexus is independent of vagus nerve and is negatively regulated by the splanchnic nerves in the rat small intestine.