Effects of long-term sennoside treatment on in vitro motility of rat colon.

Colonic motility of rats chronically pretreated with either 10 or 40 mg sennosides/kg body weight daily, 30 mg sennosides/kg twice a week or 500 mg danthron/kg daily for 6 months has been evaluated in ex vivo preparations. Registration of colonic contractions 48 h after the last application of drugs or placebo revealed striking differences between the ascending, transverse and descending parts of the colon as well as between corresponding circularly or longitudinally orientated segments. Treatment did not influence motility in the various parts of the colon except some reduction in spontaneous motility in the descending colon. Response to electrical stimulation and acetylcholine was independent of treatment in most segments, but a decrease in maximal contraction was observed by the high daily sennoside dose and by danthron in the ascending colon and descending colon, respectively. Sensitivity to rhein, an active metabolite of sennosides, was similar in all groups. Thus, chronic treatment with anthranoids reveals no abnormal motility pattern but a residual pharmacological activity 48 h after the last administration of high doses.