Pregnancy-related changes in small intestinal myoelectric activity in the rat.

To determine if changes in intestinal motility occur during pregnancy, we studied small intestinal myoelectric activity, using monopolar electrodes, in fasted pregnant rats from day 12 to day 18 of the 22-day gestation period. We also studied fasting myoelectric activity in postpartum, nonpregnant, and castrate females. In all rats, the interdigestive myoelectric complex was invariably present with recurring activity fronts appearing at the proximal electrode and moving slowly abroad. Intervals between fronts were similar in all four groups, ranging from 12.61 min to 14.58 min. In pregnant rats, however, there was loss of the periodicity characteristic of activity fronts in the other groups; intervals up to 43 min in length were occasionally noted. Unorganized, randomly occurring spike potentials characterized these intervals. The average coefficient of variation of interval length was significantly (p less than 0.05) greater in pregnant rats (0.401) than in castrate (0.197) and nonpregnant rats (0.248). These studies confirm the presence in rats of pregnancy-related changes in small intestinal myoelectric activity.