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Effect of N G ‐monomethyl l ‐arginine ( l ‐NMMA) and N G ‐nitro l ‐arginine ( l ‐NOARG) on non‐adrenergic non‐cholinergic relaxation in the circular muscle of the human ileum
Author(s) -
Maggi Carlo Alberto,
Barbanti Gabriele,
Turini Damiano,
Giuliani Sandro
Publication year - 1991
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1991.tb12361.x
Subject(s) - chemistry , arginine , biochemistry , amino acid
1 We have investigated the effect of the NO synthesis inhibitors, N G ‐monomethyl l ‐arginine ( l ‐NMMA) and N G ‐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 μ m , respectively), electrical field stimulation produced tetrodotoxin‐sensitive relaxation of the strips. l ‐NMMA, starting from 100 μ m , produced a concentration‐dependent inhibition of the evoked relaxations (2 Hz); maximal inhibition at 1 m m 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 μ m ) 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.