IN-VITRO EFFECTS OF SENNOSIDE ON CONTRACTILE ACTIVITY AND FLUID-FLOW IN THE PERFUSED LARGE-INTESTINE OF THE RAT

The effect of sodium rhein on contractile activity and fluid flow in t he rat complete large intestine was studied in vitro. Contractile acti vity was recorded using serosal strain gauges and volume transducers r ecorded distal fluid flow from the segment. Luminal sodium rhein (1 mM ) produced a protracted increase in caecal activity yet increased colo nic contractility transiently. Fluid flow from the preparation was inc reased and the number of propagated complexes was elevated after the i nitial 10 min of exposure. The effect did not appear to be related dir ectly to dose. Sodium rhein (0.1 mM) did not significantly stimulate c ontractility and a higher dose (5 mM) only produced a transient effect on propagated contractions. However, this dose had the effect of sign ificantly reducing activity when the rhein was replaced by normal buff er. The data suggest that the action of sodium rhein is subtle; after an initial excitation, the glycoside shifts the pattern of motor activ ity in favour of propulsion at the expense of segmentation. The large intestine is more able, therefore, to expel luminal contents in a caud al direction following the addition of this anthraquinone laxative.