Sensations of gas and pain and their relationship with compliance during distension in human colon

Abstract

Background: Colonic mechanosensory afferents 'in parallel' to circular muscle activate prevertebral ganglion reflexes; 'in series', afferents convey visceral sensation to the central nervous system; and pain receptors are activated with muscle distension. Our aim was to analyze the relationships of gas and pain sensations during graded distensions, and the association of sensations with colonic compliance in conscious humans.

Methods: The data were acquired in a prior study performed on 60 healthy volunteers (aged 18-75 years) under baseline conditions. Colonic compliance was measured in response to 4 mmHg stepwise balloon distensions to estimate pressure at half-maximum volume (Pr(50%)). Sensation ratings for gas and pain were averaged over distensions at 16, 24, 30 and 36 mmHg above baseline operating pressure. Associations between mean gas and pain ratings, and colonic compliance were assessed with Pearson correlations.

Key results: Gas and pain sensations were significantly correlated at all levels of distension (all P < 0.001). Significant inverse correlations between Pr(50%) and sensations of gas and pain were observed, suggesting that lower compliance was associated with lower sensations. Up to 25% of the variance in sensation may be attributed to colonic compliance.

Conclusions & inferences: These data are consistent with the hypothesis that, if circumferential colonic receptors are stimulated by distension to mediate gas and pain in humans, they are, at least partly, arranged 'in parallel' to the muscle layer.

Trial registration: ClinicalTrials.gov NCT01094808.

Conflict of interest statement

Conflicts of Interest: No conflicts of interest exist.

© 2012 Blackwell Publishing Ltd.

Figures

Figure 1

Scheme representing the activation and inactivation of mechanotranducers in series and in parallel to muscle fibers in the colon (adapted from Corsetti et al., reference 7). Note that relaxation associated with increased colonic compliance activates in parallel receptors. Whereas, distension is thought to activate both in series and in parallel receptors, it is also likely that distension results in elongation of smooth muscle cells which would potentially offload and inactivate in series transducers.

Figure 2

Relationship of sensation ratings for gas and pain averaged at each distension level. The Pearson correlations are provided with each plot and all are highly significant (p

Figure 3

Relationship of colonic compliance and mean sensation ratings for gas and pain (averaged over 4 distension levels). Note the significant inverse relationship, suggesting that sensation ratings are lower with decreased compliance (higher Pr50 is associated with lower compliance).