To clarify the role of mast cells and neuropeptides substance P (SP)

somatostatin (SS)

and vasoactive intestinal peptide (VIP) in dextran sulfate sodium (DSS)-induced colitis in rats. Methods Experimental colitis was induced in Sprague-Dawley rats (180-200 g

n=20) by oral ingestion of 4% (w/v) DSS in drinking water for 7 days. Control rats (n=5) drank water and were sacrificed on day 0. Mast cell number

histamine levels in whole blood and tissue

tissue levels of SP

SS and

VIP in the distal colon of the rats were measured on day 8

day 13

and day 18 of experimentation. Results Oral administration of 4% DSS solution for 7 days resulted in surface epithelial loss and crypt loss in the distal colon. Mast cell count increased on day 8 (1.75±1.09/mm vs. 0.38±0.24/mm

P<0.05) and day 13 (1.55±1.01/mm vs. 0.38±0.24/mm

P<0.05) after DSS treatment. Whole blood histamine levels were increased on day 8 (266.93±35.62 ng/mL vs. 76.87±32.28 ng/mL

P<0.01) and gradually decreased by day 13 and day 18 after DSS treatment. Histamine levels in the distal colon were decreased on day 8 (1.77±0.65 ng/mg vs. 3.06±0.87 ng/mg

P<0.05) and recovered to control levels by day 13 after DSS treatment. SP level in the distal colon gradually increased and were raised significantly by day 13 (8777.14±3056.14 pg/mL vs. 4739.66±3299.81 pg/mL

P<0.05) after DSS treatment. SS and VIP levels in the distal colon were not changed. Conclusions Mast cell degranulation followed by histamine release may play an important role in the pathogenesis of colitis induced by DSS. SP may be a significant substance in the progression of inflammation and the recovery process of DSS-induced colitis.