INFLAMMATION MODULATES IN-VITRO COLONIC MYOELECTRIC AND CONTRACTILE ACTIVITY AND INTERSTITIAL-CELLS OF CAJAL

Inflammation suppresses phasic contractile activity in vivo. We invest igated whether inflammation also suppresses in vitro phasic contractil e activity and, if so, whether this could in part be due to the altera tion of specific slow wave characteristics and morphology of the inter stitial cells of Cajal (ICC). Circular muscle strips were obtained fro m normal and inflamed distal canine colon. Inflammation was induced by mucosal exposure to ethanol and acetic acid. The amplitudes of sponta neous, methacholine-induced, substance P-induced, and electrical field stimulation-induced contractions were smaller in inflamed muscle stri ps than in normal muscle strips. Inflammation reduced the resting memb rane potential and the amplitude and duration of slow waves in circula r muscle cells. Inflammation did not affect the amplitude of inhibitor y junction potentials but did decrease their duration. Ultrastructural studies showed expansion of the extracellular space between circular muscle cells, reduction in the density of ICC and associated neural st ructures, damage to ICC processes, vacuolization of their cytoplasm, a nd blebbings of the plasma membrane. We conclude that inflammation-ind uced alterations of slow wave characteristics contribute to the suppre ssion of phasic contractions. These alterations may, in part, be due t o the damage to ICC. Inflammation impairs both the myogenic and neural regulation of phasic contractions.