ACTION OF SENSORY NEURONS IN AN EXPERIMENTAL RAT COLITIS MODEL OF INJURY AND REPAIR

The influence of sensory nerves on inflammation and healing was studie d in a rat colitis model at different stages of inflammation. Studies were performed in animals with and without ablation of sensory nerves, which was achieved by pretreatment with the neurotoxin capsaicin. Col itis was induced by a rectal enema containing trinitrobenzenesulfonic acid (50 mg/kg) in 50% ethanol. Severity of inflammation was markedly increased 3 and 7 days after induction of colitis in the capsaicin-pre treated group compared with the vehicle group as determined by a macro scopic damage score (at 3 days, 12.0 +/- 0.7 vs. 7.5 +/- 1.5; at 7 day s, 12.2 +/- 0.8 vs. 6.5 +/- 0.8; P < 0.05), by histology (ulceration s core at 3 days, 82 +/- 12 vs. 40 +/- 11%; at 7 days, 92 +/- 5 vs. 46 /- 13%; P < 0.05), and by myeloperoxidase activity (at 3 days, 133 +/- 30 vs. 42 +/- 14 U/mg protein; at 7 days, 76 +/- 11 vs. 39 +/- 11 U/m g protein; P < 0.05). There was no significant difference in the sever ity of colitis 14 and 21 days after induction of colitis between the c apsaicin-pretreated group and the vehicle group. These data suggest th at, in this model, sensory nerves have an important protective functio n in the acute and subacute phases of inflammation but do not seem to play a significant role in the later stages of chronic inflammation.