Sensitization by caerulein of guinea-pig ileum to contractions by acetylcholine, histamine, 5-hydroxytryptamine and nicotine.

Low concentrations (0.63 and 1.25 ng/ml) of caerulein increase the submaximal contractions of the guinea-pig isolated ileum induced by several agonists and electrical stimulation. These effects of the polypeptide are due partly to neuronal pathways (i.e., a ganglionic stimulation) and partly to a non specific muscular sensitization. At higher concentrations of caerulein the effects of all the agonists were decreased. This seems related to the contractile effect of the peptide itself on the longitudinal muscle which interfers non specifically with the development of contractions induced by any other agonist.