Pharmacological characterization of ketotifen effects on guinea pig ileum

The effects of Ketotifen (Ke) on the contraction of isolated guinea pig ileum induced by electrical stimulation, nicotine or acetylcholine have been investigated. Ke (10(-6)-10(-5) M) inhibited electrically-induced contractions. Prostaglandin F2 alpha, when added to the bath shortly after Ke, reversed this effect. Furthermore, Ke significantly inhibits guinea pig ileum contractions induced by nicotine and acetylcholine both on innervated and denervated ileal strips. These results suggest that Ke influence on ileum contractions is mediated either by inhibition of acetylcholine release from postganglionic parasympathetic fibres of ileum or by anticholinergic effect (atropine-like action). The inhibitory effect of Ke against acetylcholine-induced contractions is in favor of the latter possibility, although nonspecific membrane stabilizing effect might be also involved in the mode of Ke action.