Development of colorectal sensitization is associated with increased eosinophils and mast cells in dextran sulfate sodium-treated rats.

We used conscious restrained rats, in which balloon distension of the colorectum was used as a repeated visceral stimulus over a 21-day period, either alone or in conjunction with a luminal irritant, dextran sodium sulfate (DSS), in order to elicit sensitization as evidenced by amplified blood pressure responses. Female Sprague Dawley rats received 5% DSS in the drinking water for 3 days. A water-filled balloon was used to distend the colorectum. Set volumes (1, 1.5, and 2 mL) were applied for 3 min, at 10-min intervals, weekly for 3 weeks, with colorectal and tail-cuff blood pressures measured. Tissue for mast cell localization and histology were taken from proximal and distal colon at sacrifice. Mean colorectal balloon pressures and blood pressures in the DSS-treated rats compared to controls were 12% (P < 0.01) and 64% (P < 0.03) higher, respectively. At sacrifice the DSS-treated rats had twice the number of mast cell numbers in the mucosa of the proximal colon compared to controls, suggesting that the sensitization effect may be linked to inflammatory mediators (P < 0.05).