Neuronal Nitric Oxide Synthase-Derived Nitric Oxide Is Involved in Gastric Mucosal Hyperemic Response to Capsaicin in Rats

Background and Aims: Activation of transient receptor potential vanilloid type 1 (TRPV1) by capsaicin leads to gastric hyperemic response through capsaicin-sensitive sensory nerves and nitric oxide (NO). The aim of the present study is to examine which isoform of nitric oxide synthase (NOS)/NO is involved in the hyperemic response to capsaicin in the rat stomach. Methods: Gastric mucosal blood flow (GMBF) was measured by laser Doppler flowmetry in rats. The localizations of TRPV1 and neuronal NOS (nNOS) in the rat gastric mucosa were detected by immunohistochemical staining. Results: The nNOS inhibitor N-5-[imino(propylamino) methyl]-L-ornithine substantially reduced GMBF during capsaicin application, whereas the endothelial NOS (eNOS) inhibitor N-5-(1-iminomethyl)-L-ornithine did not affect the effect of capsaicin during the application. The nonselective NOS inhibitor N-G-nitro-L-arginine methyl ester apparently inhibited the capsaicin-induced GMBF, while the inducible NOS inhibitor 1400W did not affect GMBF response to capsaicin. The immunohistochemical studies revealed nerve fibers coexpressing TRPV1 and nNOS around blood vessels in the gastric submucosa. Conclusion: We demonstrated for the first time that nNOS/NO is involved in gastric hyperemic responses to capsaicin. Copyright (c) 2013 S. Karger AG, Basel