Mechanical Visceral Pain Model: Chronic Intermittent Intestinal Distention in the Rat

Animal models designed to test the effectiveness of analgesic agents against viceral pain typically rely on a noxious chemical irritation of the peritoneum, e.g., acetic acid and phenylquinone writhing tests. While useful, this type of assay depends upon an acute inflammation and the release of local alogens. Further, ethical and scientific constraints prevent repeated assessments in a single animal, thereby compounding the difficulty of assessing tolerance development to analgesic agents. To overcome these constraints we developed a model for mechanical visceral pain (VPM) based on a repeatable and reversible duodenal distention in the rat. A chronic indwelling intraduodenal balloon catheter is well tolerated and upon inflation produces a writhing response graded in proportion to distention. This response is inhibited by morphine in a dose dependent manner.