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Haustral boundary contractions in the proximal 3-taeniated rabbit colon.

Chen JH, Yang Z, Yu Y, Huizinga JD.

Am J Physiol Gastrointest Liver Physiol. 2016 Feb 1;310(3):G181-92

PMID:26635318

Abstract

The rabbit proximal colon is similar in structure to the human colon. Our objective was to study interactions of different rhythmic motor patterns focusing on haustral boundary contractions, which create the haustra, using spatiotemporal mapping of video recordings. Haustral boundary contractions were seen as highly rhythmic circumferential ring contractions that propagated slowly across the proximal colon, preferentially but not exclusively in the anal direction, at ∼0.5 cycles per minute; they were abolished by nerve conduction blockers. When multiple haustral boundary contractions propagated in the opposite direction, they annihilated each other upon encounter. Ripples, myogenic propagating ring contractions at ∼9 cycles per min, induced folding and unfolding of haustral muscle folds, creating an anarchic appearance of contractile activity, with different patterns in the three intertaenial regions. Two features of ripple activity were prominent: frequent changes in propagation direction and the occurrence of dislocations showing a frequency gradient with the highest intrinsic frequency in the distal colon. The haustral boundary contractions showed an on/off/on/off pattern at the ripple frequency, and the contraction amplitude at any point of the colon showed waxing and waning. The haustral boundary contractions are therefore shaped by interaction of two pacemaker activities hypothesized to occur through phase-amplitude coupling of pacemaker activities from interstitial cells of Cajal of the myenteric plexus and of the submuscular plexus. Video evidence shows the unique role haustral folds play in shaping contractile activity within the haustra. Muscarinic agents not only enhance the force of contraction, they can eliminate one and at the same time induce another neurally dependent motor pattern.

This paper elucidates the nature of the haustra of the colon. The haustra of the colon are separated by rhythmically contracting bands of circular muscle, controlled by a network of ICC as well as the ENS. While slowly propagating distally, they interact with another rhythmically contracting pattern, controlled by a different ICC pacemaker network so that a unique haustral boundary motor pattern develops. This is probably the major motor pattern promoting absorption and stool formation.

Every drawing of the colon points to “haustra”.But what are they and what role do they play in colon function? In Jihong Chen’s laboratory at Wuhan University, two of her students, co-supervised by Jan Huizinga, studied this in the rabbit colon which is very similar in structure to the human colon. Haustra are pockets that are separated by rhythmically contracting, slowly propagating, bands of circular muscle. This, together with other motor patterns, creates perfect mixing in the pockets while very slowly moving content distally. We hypothesize that poor stool formation is caused by abnormalities in haustral boundary contractions.

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