In vivo motility of rat colon chronically pretreated with sennosides. 
Ceco-colonic myoelectrical activity was investigated in rats pretreated for 23 weeks by sennosides (10 or 40 mg/kg/day), Na-picosulfate (2.5 or 10 mg/kg/day) or laxative vehicle (control).  On the last week of treatment the animals were equipped with Nichrome electrodes on the cecum, the proximal and distal colon.  In comparison with controls, sennoside or Na-picosulfate treatment did not induce any significant (p > 0.05) change in the duration of long spike bursts (LSB) which are associated with phasic contractions.  On the last 2 days of treatment the frequency of LSB for 2 h before and 2 h after laxative administration, as well as for 30 min after a 3-gram meal was not significantly (p > 0.05) different in control and treated animals.  Similarly, on the first 2 days, as well as on days 13 and 14, after the end of treatment, no significant (p > 0.05) difference in the LSB frequency appeared between control and treated animals, in the fasted state or after a 3-gram meal.  It is concluded that long-term treatment with sennosides or Na-picosulfate does not induce chronic changes in colonic motility in rats.