Vincristine alters myoelectric activity and transit of the small intestine in rats.

We investigated the motility of the small intestine in unanesthetized rats receiving vincristine (0.075, 0.50, 0.75 mg/kg i.v.). Motility was determined by two methods: myoelectric activity was monitored with indwelling bipolar electrodes, and intestinal transit was measured by the movement of radiochromium (Na51CrO4). Only the animals injected with the two higher doses had two distinct patterns of altered intestinal myoelectric activity within 2 h of drug administration. The first alteration occurred 44 +/- 6 min after vincristine administration and consisted of a marked increase in action potential activity with disruption of the migrating myoelectric complex. The second alteration consisted of a reappearance of the activity front of the migrating myoelectric complex with a significantly shorter periodicity. A marked reduction in spike activity occurred 3 days after vincristine injection in 3 of 10 animals receiving vincristine. A biphasic response was noted in intestinal transit. Disrupted activity front formation was associated with a significant delay in small bowel transit. In contrast, frequent activity front formation in rats was associated with significantly hastened transit. In summary, vincristine administration induces alterations of myoelectric activity of the small intestine in fasted rats and is associated with changes in intestinal transit.