The opioid κ-selective compound U−50,488H does not inhibit intestinal propulsion in rats

Abstract
The selective κ-compound U−50,488H, at doses producing strong central pharmacological effects (0·5–32 mg kg−1 i.p.) did not delay the intestinal transit of a charcoal meal and had little or no antagonist action against morphine-induced constipation. It appears that κ-opioid receptors are probably not involved in the mechanisms responsible for opioid-induced constipation.