Behavioral evaluation of visceral pain in a rat model of colonic inflammation

A new rat model was established up to evaluate the antinociceptive effect o f compounds in visceral pain. The test consisted in measuring the performan ce of rats in an aversive light stimulus avoidance experimental device. Rat s with TNBS-induced colitis had a lower number of total active lever pressi ngs and did not discriminate the active lever from the inactive one. Morphi ne (1 mg/kg, s.c.) and CI-977 (0.001 mg/kg, s.c.) treatment restored the le vel of pressing activity of animals and their ability to discriminate the a ctive lever from the inactive one. Naloxone treatment antagonized the impro vement of performance produced by morphine. The results obtained indicate t hat this behavioral paradigm may be used to evaluate the antinociceptive po tential of compounds. NeuroReport 10:1137-1141 (C) 1999 Lippincott Williams & Wilkins.