Functional role of inducible nitric oxide synthase on mouse colonic motility

A possible functional role of inducible isoform of nitric oxide synthase (i NOS) was explored in vitro on the motility of mouse distal colon. Using an isotonic - non-isovolumic technique, peristaltic activity and video images of the external wall of colonic segments were recorded before and after add ition to the medium of Aminoguanidine (AG) and N-(3-(aminomethyl)benzyl) ac etamidine (W1400) [10(-7) M-10(-4) M], two iNOS inhibitors. AG and W1400 in duced an hyperexcitability of visceral smooth muscle characterised by an in crease of basal tone and spontaneous phasic activity. As a consequence of t hese effects, the peristaltic activity declined and disappeared at the high est concentrations. These findings indicated a removal of inhibitory action performed by NO synthesised by MOS in the colonic segment. The implication s of results are discussed in term of tonic relaxation of intestinal smooth muscle to allow intraluminal content accommodation. (C) 2001 Elsevier Scie nce Ireland Ltd. All rights reserved.