Circadian rhythm of colonic motility in the cat.

Since circadian patterns of colonic motility are largely unknown the electrical activity of the colon musculature was recorded in 6 unanesthetized cats during day and night. All parts of the colon exhibited 6 patterns of electrical activity: spikes, oscillations, omnipresent regular slow waves, and three composite patterns, i.e. a minute-rhythmic activity, activity complexes of 1 to 18 minute duration and a nyctohemeral pattern. The circadian rhythm was different between the proximal and distal colon resulting in activity gradients. These were directed in an aborad direction from 7 to 9 a.m. and from 9 p.m. to midnight. Most of the defecations of the 6 cats occured in the late evening until 1 a.m. Spike activity of the distal colon predominated from 3 to 4 a.m. and from 11 a.m. to 5 p.m. It is concluded that a circadian rhythm exists in the motility of the cat colon. Differences in the activity between the proximal and the distal colon and resulting activity gradients may offer an explanation for the influences of the time of day on the timing of defecations.