Noradrenaline inhibits neurogenic propulsive motor patterns but not neurogenic segmenting haustral progression in the rabbit colon

A novel mechanism for acute colonic pseudo-obstruction revealed by high-resolution manometry: A case report

BACKGROUND

Acute colonic pseudo-obstruction (ACPO) is a severe form of colonic dysmotility and is associated with considerable morbidity. The pathophysiology of ACPO is considered to be multifactorial but has not been clarified. Although colonic motility is commonly assumed to be hypoactive, there is little direct pathophysiological evidence to support this claim.

METHODS

A 56-year-old woman who developed ACPO following spinal surgery underwent 24 h of continuous high-resolution colonic manometry (1 cm resolution over 36 cm) following endoscopic decompression. Manometry data were analyzed and correlated with a three-dimensional colonic model developed from computed tomography (CT) imaging.

RESULTS

The distal colon was found to be profoundly hyperactive, showing near-continuous non-propagating motor activity. Dominant frequencies at 2-6 and 8-12 cycles per minute were observed. The activity was often dissociated and out-of-phase across adjacent regions. The mean amplitude of motor activity was higher than that reported from pre- and post-prandial healthy controls. Correlation with CT imaging suggested that these disordered hyperactive motility sequences might act as a functional pseudo-obstruction in the distal colon resulting in secondary proximal dilatation.

CONCLUSIONS

This is the first detailed description of motility patterns in ACPO and suggests a novel underlying disease mechanism, warranting further investigation and identification of potential therapeutic targets.

Intraluminal prucalopride increases propulsive motor activities via luminal 5-HT4 receptors in the rabbit colon

BACKGROUND

Activating luminal 5-HT₄ receptors results in the release of 5-HT from enterochromaffin cells into the lamina propria to modulate colonic motility. Our aim was to evaluate characteristics of colonic motor patterns involved in the prokinetic effects of intraluminal prucalopride in the rabbit colon.

METHODS

Colonic motor patterns were studied ex vivo using simultaneous spatiotemporal diameter mapping and pressure sensing.

KEY RESULTS

Intraluminal prucalopride and intraluminal exogenous 5-HT strongly evoked or enhanced the colonic motor complex at all levels of excitation beginning with generation of clusters of fast propagating contractions (FPCs), then development of long-distance contractions (LDCs) within the clusters, and finally forceful LDCs as the highest level of excitation. Intraluminal prucalopride and intraluminal exogenous 5-HT stimulated propulsive motor activity in a dose-dependent and antagonist-sensitive manner by increasing the contraction amplitude, intraluminal pressure, frequency, velocity, and degree of propagation of the colonic motor complex.

CONCLUSIONS AND INFERENCES

Activating mucosal 5-HT₄ receptors via intraluminal prucalopride or 5-HT increases propulsive motor activity in a graded manner; that is, depending on starting conditions, amplitudes or frequencies of an activity may increase or a new pattern may be initiated. Our data support further studies into delivering 5-HT₄ receptor agonists via colon-targeted drug delivery systems and studies into the role of luminal 5-HT as an essential requirement for normal colon motor pattern generation.