Naloxone and intestinal motility

It was supposed that the inhibition of intestinal peristalsis seen in animals and humans after abdominal surgery might be related to the release of endorphins, endogenous opiate receptor agonists, caused by the surgical stress and pain. However, naloxone, a potent morphine and endorphin antagonist, failed to block this peristaltic inhibition in rats, which leaves the mechanism of this inhibition, and thus the function of intestinal endorphins, still very much in doubt.