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 μ M ), 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 m M ) 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.