Oxazolone-induced colitis in rats:: Effects of budesonide, cyclosporin A, and 5-aminosalicylic acid acid

Background: The intention of the present study was to develop a new hapten-based inflammatory bowel disease model in the rat, useful for pharmacologic screening of new substances with anti-inflammatory properties and immunomodulating capacities. It was considered important to avoid the use of an irritating barrier breaker, such as ethanol. Methods: Dark Agouti rats were skin-sensitized with oxazolone and further challenged intra-rectally with oxazolone dissolved in carmellose sodium (Orabase(R))/peanut oil. The effects of treatment with budesonide, prednisolone, cyclosporin A, and 5-aminosalicylic acid (5-ASA) were studied. Results: The intra-rectal challenge with oxazolone in sensitized rats induced an inflammation with an increased colon wet weight, pronounced myeloperoxidase (MPO) activity, and hyperemia/ulcerations in the epithelial lining. Improvement was achieved by treatment with budesonide, prednisolone, and cyclosporin A but not with 5-ASA. Conclusions: The model fulfills the criteria for a fast, reproducible animal model for human colon inflammation, suitable for pharmacologic screening and studies of an immune-driven colon inflammation.