Inhibition of intestinal smooth muscle contraction by surface-active alkyltrimethylammonium salts

The effects of surface-active alkyltrimethylammonium salts (C10--C20) on the contractile activity of isolated rat jejunum and on the gastrointestinal motility in anaesthetized rats were studied. The surfactants caused a dose-dependent depression of spontaneous contractions and of acetyl-beta-methylcholine and BaCl2 induced contractions of isolated rat jejunum. The depressant activity of the surface-active alkyltrimethylammonium salts on smooth muscle contraction increased with an increase in the length of the alkyl chain to maximum activity at C16. It is suggested that the depressant activity of the surface-active alkyltrimethylammonium salts on smooth muscle contraction is due to a non-specific interaction of the surfactants with the cellmembrane of the muscle cells. No effect on gastric and intestinal motility in vivo was observed following intragastric or intraintestinal administrations of surface-active alkyltrimethylammonium salts. This lack of effect upon intraintestinal or intragastric administration probably depends on an inability of the surfactants to reach the site of action when administered from the mucosal side.