Effect of NG‐monomethyl l‐arginine (l‐NMMA) and NG‐nitro l‐arginine (l‐NOARG) on non‐adrenergic non‐cholinergic relaxation in the circular muscle of the human ileum

Open Access
Publisher Website
Google Scholar
Abstract
1 We have investigated the effect of the NO synthesis inhibitors, NG-monomethyl l-arginine (l-NMMA) and NG-nitro l-arginine (l-NOARG) on the non-adrenergic non-cholinergic (NANC) relaxation produced by electrical field stimulation in the circular muscle of the human ileum. 2 In the presence of atropine and guanethidine (1 and 3 μm, respectively), electrical field stimulation produced tetrodotoxin-sensitive relaxation of the strips. l-NMMA, starting from 100 μm, produced a concentration-dependent inhibition of the evoked relaxations (2 Hz); maximal inhibition at 1 mm averaged about 35%. 3 The inhibitory effect of l-NMMA was unchanged by previous incubation with d-arginine while it was prevented by l-arginine (l-Arg). l-NMMA did not affect isoprenaline-induced relaxation. 4 l-NOARG (1–30 μm) concentration-dependently inhibited the evoked relaxations at 2 Hz, up to a maximum of 65% inhibition, although in some strips complete inhibition of the response was observed. The effect of l-NOARG was reversed by l-Arg. l-NOARG did not affect isoprenaline-induced relaxation. 5 These results suggest that NO may be involved in inhibitory NANC transmission in the circular muscle of the human ileum.

This publication has 14 references indexed in Scilit: