Regional Differences in Intestinal Contractile Responses to Radial Stretch in the Human Lower Gastrointestinal Tract

Background/Aims Radial stretch evokes an increase or decrease in contractions in the lower gastrointestinal tract via mechanosensory enteric neurons that project into the muscle layers. We aim to elucidate the differences in stretch reflexes according to their location in the human colon.Methods We used healthy intestinal smooth muscle tissue excised during elective colon cancer surgery. Conventional intracellular recordings from colonic muscle cells and tension recordings of colonic segments were performed. Radial stretch was evoked through balloon catheter inflation. Changes in the membrane potential and frequency, amplitude, and area under the curve of muscle contractions were recorded before and after the radial stretch at proximal and distal segment sites.Results In intracellular circular muscle recordings, hyperpolarization was noted at the distal site of sigmoid colonic segments after radial stretch, in contrast to depolarization at all other sites. In tension recordings at proximal ascending or sigmoid colonic segment sites, contractile activation was observed with statistically significant increases in the frequency, amplitude, and area under the curve after radial stretch. Distal sites of ascending and sigmoid colonic segments showed increase and decrease in contraction, respectively.Conclusion Radial stretch in the human colon (in vitro) evokes excitatory activity at both proximal and distal sites of the ascending colon and at the proximal site of the sigmoid colon, whereas it elicits inhibitory activity at the distal site of the sigmoid colon.(J Neurogastroenterol Motil 2023;29:113-121)

Automated summary

In this study, differences in stretch reflexes in the human colon were investigated. It was found that radial stretch induced hyperpolarization in the distal site of sigmoid colonic segments, while depolarization was observed in all other sites. Tension recordings also showed that contractile activation increased at proximal ascending or sigmoid colonic segment sites after radial stretch, while the distal site of ascending and sigmoid colonic segments exhibited both increase and decrease in contraction, respectively. Overall, radial stretch in the human colon evokes excitatory activity at certain sites and inhibitory activity at others.