REVERSAL BY KAPPA-AGONISTS OF PERITONEAL IRRITATION-INDUCED ILEUS ANDVISCERAL PAIN IN RATS

Peritoneal irritation in rats induced by i.p. administration of acetic acid produces abdominal contractions reflecting visceral pain, and ga strointestinal ileus characterized by inhibition of gastric emptying a nd small intestine transit. In this study, gastric emptying (GE) and i ntestinal transit, calculated by the geometric center (GC) method, wer e estimated using a test meal labeled with Cr-51-EDTA. Visceral pain w as assessed by counting abdominal contractions. Acetic acid produced a bdominal contractions (80.8 +/- 3.3) and inhibition of GE (-54%) and G C (-63%) during the test-period. The mu-opioid receptor agonists, CI-9 77, (+)-U-50,488H, (+/-)-bremazocine, PD-117,302, (-)-cyclazocine, and U-69,583, reversed abdominal contractions and inhibitions of gastroin testinal transit in a dose-related manner. The mu-opioid receptor agon ists and potent analgesics, morphine and fentanyl did not restore norm al gastric emptying and intestinal transit. These data suggest that se lective kappa-opioid receptor agonists might be used to treat abdomina l pain associated with motility and transit impairment during postoper ative ileus.