Synergistic opioid inhibition of colonic Cl- secretion by kappa-opioid receptor agonism plus mu-opioid receptor antagonism.

On the basis of the novel concept of a dual prosecretory/antisecretory intestinal opioid system, a voltage-clamp experiment was performed with guinea-pig colonic mucosa, and net anion (Cl-) secretion was measured after stimulation with prostaglandin E1 (PGE1) plus theophylline. Synergism between kappa-opioid receptor agonism by U69593 and mu-opioid receptor antagonism by CTOP-NH2 (D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH2) was observed.