ROLE OF NITRIC-OXIDE ON CHOLINERGIC COMPONENT OF BRONCHIAL TONE IN PIG

In vitro studies demonstrated that stimulation of intrinsic nerves of airway smooth muscle results in a predominantly contractile response, followed by a relaxant response which involves cholinergic, adrenergic and non-adrenergic non-cholinergic (NANC) nerve activation. Thus, in this paper it is determined whether endogenous nitric oxide (NO) modul ates cholinergic neurotransmission in isolated pig airway smooth muscl e. Bronchial rings were suspended in organ baths for isometric measure ment of tension and the contractions were induced using electrical fie ld stimulation (EFS) techniques. Then, the effects of L-N-G-nitroargin ine (L-NOARG, 10 mu M), an inhibitor of NO synthase, and L-arginine (L -ARG, 1 mM), a precursor of NO synthesis, were evaluated. The choliner gic contractions induced by electrical field stimulation (EFS: 60 V, 2 ms, 60 Hz) of pig lobar bronchial preparations increased (29%) in the presence of L-NOARG (10 mu M). This effect may be released by nerves in pig large airways during EFS. (C) 1996 The Italian Pharmacological Society.