Opiate receptors and endogenous opiates (endorphins) have been demonstrated recently in human colon but their role in motility is not known. In patients with the Irritable Bowel Syndrome (IBS) balloon distension of the rectosigmoid elicits active contractions that are similar to those seen in normal subjects given exogenous opiates (morphine). To assess the possible pathophysiologic role of endogenous opiate activity on the abnormal motor pattern of IBS, the effect of a pure opiate antagonist, naloxone, on colonic motility in controls and patients with IBS was determined. Rectosigmoid pressures were recorded with a balloon tipped catheter at the recto-sigmoid junction. Air was injected into the balloon every two minutes in 20 ml increments until active contractions were elicited (irritability threshold). All subjects then received intravenously 10 mg naloxone or placebo in a randomized blinded fashion. The colon motility study was repeated and a post injection threshold determined. In six controls naloxone did not alter the normal colonic motility pattern. In the IBS group, naloxone significantly increased the irritability threshold from a baseline of 51.4 ± 13.0 cc of air to 94.3 ± 15.6cc (P < .05). Placebo produced no significant change with a baseline of 63.3 ± 15.4 cc and a post-placebo irritability threshold of 53.3 ± 18.3 cc ( P > .05). Thus the effect of naloxone on colonic motility is to shift the irritability threshold upwards in IBS patients. We suggest that these findings are consistent with the hypothesis that increased endogenous opiate activity may play a role in the pathogenesis of the irritable bowel syndrome.
|Original language||English (US)|
|Number of pages||1|
|Issue number||5 II|
|State||Published - Jan 1 1979|
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