Distinct patterns of myogenic motor activity identified in isolated human distal colon with high-resolution manometry.

Abstract

Colonic high-resolution manometry (HRM) has been used to reveal discrete, propagating colonic motor patterns. To help determine mechanisms underlying these patterns, we used HRM to record contractile activity in human distal colon ex vivo. Surgically excised segments of descending (n=30) or sigmoid colon (n=4) were immersed in oxygenated Krebs solution at 36°C (n=34; 16 female; 67.6±12.4years; length: 24.7±3.5cm). Contractility was recorded by HRM catheters. After 30minutes of baseline recording, 0.3mM lidocaine and/or 1mM hexamethonium were applied. Ascending neural pathways were activated by electrical field stimulation (EFS; 10Hz, 0.5ms, 50V, 5-s duration) applied to the anal end before and after drug application. Spontaneous propagating contractions were recorded in all specimens (0.1-1.5 cycles/minute). Most contractions occurred synchronously across all recording sites. In five specimens, rhythmic antegrade contractions propagated acrossthe full length of the preparation. EFS evoked local contractions at the site of stimulation (latency: 5.5±2.4seconds) with greater amplitude than spontaneous contractions (EFS; 29.3±26.9 vs 12.1±14.8mm Hg; P=.02).Synchronous or retrograde propagating motor patterns followed EFS; 71% spanned the entire preparation length. Hexamethonium and lidocaine modestly and only temporarily inhibited spontaneous contractions, whereas TTX increased the frequency of contractile activity while inhibiting EFS-evoked contractions. Our study suggests that the propagated contractions recorded in the organ bath have a myogenic origin which can be regulated by neural input. Once activated at a local site, the contractions do not require the propulsion of fecal content to sustain long-distance propagation.