Functional effects of dextran sulphate sodium (DSS) treatment on the longitudinal muscle of rat distal colon

1. The current study addressed how acute colitis, induced in male Sprague-Dawley rats by the administration of dextran sulphate sodium (DSS) in their drinking water, may affect some functional properties of the longitudinal muscle layer of the distal colon. 2 Dextran sulphate sodium was provided at a concentration of 3% for 3 or 7 days, or 5% for 7 days, and the rats were thereafter killed. Specimens of the distal colon were taken for histology or for organ bath experiments. 3 The colitis score increased significantly with increasing dose of DSS administered. At 5% concentration, there was sometimes even transmural inflammation. Functionally, there was a progressive increase in optimal preload (P-o) for the contractile response to carbachol (1 mum), in relation to the severity of the colitis. At 5% DSS, the magnitude of the response to carbachol at P-o was significantly increased compared with control rats. Such an effect could not be verified when, instead, K+ (60 mM) was used as a spasmogen. 4 It is concluded, that the colitis score increased in severity progressively with increasing amounts of DSS administered. The longitudinal muscle layer was functionally affected by the inflammation. Thus, there was a progressive increase in optimal preload for muscle contraction. Moreover, severe colitis resulted in an increase of the contractile response to carbachol, while a significant increase in the response to depolarization with K+ could not be found.