Effects of laxative and nonlaxative hydrophilic polymers on canine small intestinal motor activity

Bulk-forming laxatives increase fecal volume and elicit aborally directed colonic motility patterns. Recently, it was demonstrated that test meals of the bulk-laxative fibers (cellulose and bran) elicited organized jejunal motor activity while nonlaxative fiber meals (guar) elicited unorganized jejunal motor activity. However, whether bulk-forming laxatives, as a class of compounds, differentially affect small intestinal motility has not been studied. Therefore, a study was made of the effects of the bulk laxatives psyllium and polycarbophil and the nonlaxative pectin on canine jejunal motor activity. Psyllium and pectin are examples of dietary fiber, while polycarbophil is a synthetic polymer. Pectin and psyllium test meals presented as viscous gels. In contrast, polycarbophil meals presented as a combination of discrete particles plus meal water. After each meal, measurements were made of the jejunal motility index, the time of reappearance of interdigestive burst activity, and overall motility patterns. Pectin and psyllium meals increased in viscosity as meal fiber content increased. As meal content and hence viscosity increased, both the laxative (psyllium) and nonlaxative (pectin) fiber meals elicited increasing jejunal motor activity and delays in the reappearance of the burst interval. For both fiber types, motor activity presented as randomly appearing contractions. In contrast, meals of the laxative polycarbophil elicited no more motor activity than the saline control meal. However, this control-level amount of activity presented as propagated clusters of contractions, ie, the "laxative-induced pattern." Polycarbophil did not delay the reappearance of burst activity.(ABSTRACT TRUNCATED AT 250 WORDS)