Circadian variation in the propagation velocity of the migrating motor complex

Using twin intraluminal pressure-sensitive radiotelemetric capsules for prolonged monitoring of proximal small bowel motility in healthy volunteers, we observed a significant (p less than 0.001) variation between daytime (6.44 +/- 0.74 cm/min, mean +/- SD) and nocturnal (2.90 +/- 0.35 cm/min) propagation velocities of the migrating motor complex. An identical variation in propagation velocity was observed in patients suffering from the irritable bowel syndrome. These data suggested a circadian variation, but did not exclude alternative hypotheses. Data were therefore compiled from healthy sheep and pigs supplied with ad libitum rations each morning and adapted to a 12 h light, 12 h dark schedule. Recording from implanted electrodes showed a significant (p less than 0.01) reduction in migrating motor complex velocity from 27.8 +/- 5.1 cm/min by day to 16.7 +/- 3.1 cm/min at night in sheep, and from 20.6 +/- 2.4 to 13.4 +/- 1.9 cm/min in pigs. The nocturnal reduction remained when the animals were fed in the evening. These observations suggest a circadian variation in mammalian migrating motor complex propagation velocity that is not merely a function of variation in intraluminal content.