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

<b><i>Background and Aims:</i></b> 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. <b><i>Methods:</i></b> 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. <b><i>Results:</i></b> The nNOS inhibitor N⁵-[imino(propylamino)methyl]-L-ornithine substantially reduced GMBF during capsaicin application, whereas the endothelial NOS (eNOS) inhibitor N⁵-(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. <b><i>Conclusion:</i></b> We demonstrated for the first time that nNOS/NO is involved in gastric hyperemic responses to capsaicin

Peripheral Corticotropin-Releasing Factor Receptor Type 2 Activation Increases Colonic Blood Flow Through Nitric Oxide Pathway in Rats

BACKGROUND: Corticotropin-releasing factor (CRF) peptides exert profound effects on the secretomotor function of the gastrointestinal tract. Nevertheless, despite the presence of CRF peptides and receptors in colonic tissue, their influence on colonic blood flow (CBF) is unknown. AIM: To determine the effect and mechanism of members of the CRF peptide family on CBF in isoflurane-anesthetized rats. METHODS: Proximal CBF was measured with laser Doppler flowmetry simultaneously with mean arterial blood pressure (MABP) measurement. Rats were injected with intravenous human/rat CRF (CRF(1)>CRF(2) affinity), mouse urocortin 2 (mUcn2, selective CRF(2) agonist) or sauvagine (SVG, CRF(2)>CRF(1) affinity) at 1 – 30 μg/kg. The nitric oxide (NO) synthase inhibitor, L-NAME (3 mg/kg, iv), the cyclooxygenase inhibitor, indomethacin (Indo, 5 mg/kg, ip) or selective CRF(2) antagonist, astressin(2)-B (Ast(2)B, 50 μg/kg, iv) was given before SVG injection (10 μg/kg, iv). RESULTS: SVG and mUcn2 dose-dependently increased CBF while decreasing MABP and colonic vascular resistance (CVR). CRF had no effect on CBF, but increased CVR. The hyperemic effect of SVG was inhibited by L-NAME but not by Indo, whereas hypotension was partially reduced by L-NAME. Sensory denervation had no effect on SVG-induced changes. Ast(2)B inhibited SVG-induced hyperemia and decreased CVR, and partially reduced the hypotension. CONCLUSIONS: Peripheral CRF(2) activation induces colonic hyperemia through NO synthesis, without involving prostaglandin synthesis or sensory nerve activation, suggesting a direct action on the endothelium and myenteric neurons. Members of the CRF peptide family may protect the colonic mucosal via the activation of the CRF(2) receptor