Stimulation of colonic peristalsis by vasopressin: electromyographic study in normal subjects and patients with chronic idiopathic constipation

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Abstract
The effects of vasopressin on colonic motility were investigated in 6 healthy subjects and 10 patients with chronic idiopathic constipation. Recordings of the colonic myoelectric spiking activity were performed by means of 50-cm long silastic tube, equipped with four bipolar ring electrodes fixed at 10-cm intervals, which was introduced by flexible colonoscopy into the left colon. Tracings were obtained for 1 h in the fasting state and for another hour after an intramuscular injection of a pharmacological dose of vasopressin (0.3 U/kg). The different types of spike bursts generated by the colonic smooth muscle were compared before and after vasopressin injection. In both controls and patients, the tracings showed (i) rhythmic stationary spike bursts (RSB) that were seen at only one electrode site; and (ii) sporadic bursts that were either propagating over all four electrodes (SPB) or nonpropagating (SNPB). Injection of vasopressin in controls was followed for 30 min by a significant increase in the number of propagating bursts from 2.7 ± 0.6 (mean ± SEM) to 5.2 ± 1.4 bursts (p < 0.05); RSB and SNPB were not altered by vasopressin. In the constipated patients, the number of propagating bursts during the control period was significantly lower (0.8 ± 0.2 bursts/30 min) than in the volunteers (p < 0.05). After vasopressin, there was a significant increase to 3.6 ± 0.8 bursts/30 min(p < 0.001); RSB and SNPB also did not show significant alteration after vasopressin. Finally, 4 out of the 10 patients passed stools during the recording session. Since propagating bursts are known to be associated with colonic propulsion, these results indicate that vasopressin at pharmacological doses may stimulate colonic peristalsis and therefore, may be useful in the treatment of some severe idiopathic constipations.

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