The contractile effect of fedotozine on guinea pig isolated intestinal cells is not mediated by kappa opioid receptors

The compound fedotozine, recently described as a peripheral kappa opioid receptor agonist, was tested on smooth muscle cells isolated from the longitudinal muscle layer of the guinea pig ileum, in comparison with the selective kappa receptor agonist, compound U-50488. Fedotozine (1 nmol/l - 1 mu mol/l) caused a concentration-dependent contraction of intestinal cells, with a maximum decrease in cell length not significantly different from that caused by acetylcholine. The kappa agonist U-50488 (0.1 pmol/l-100 nmol/l) was without effect. The contractile effect of fedotozine was not significantly modified by naloxone (0.1-1 mu mol/l). These results indicate that fedotozine can have direct excitatory effects on intestinal smooth muscle cells from the guinea pig ileum not mediated by activation of kappa opioid receptors.