Intestinointestinal inhibitory reflexes - Effect of distension on intestinal slow waves

The motor response induced by intraluminal distension of the small intestin e has been well investigated. However, little is known of the myoelectrical response to intraluminal distension. The aim of this study was to investig ate the effects of oral- and anal-side distension on jejunal slow waves in dogs. The study was performed in 10 healthy female hound dogs implanted wit h three pairs of electrodes on the jejunum and an intestinal fistula. The f irst study session was designed to investigate the effects of anal-side dis tension on jejunal myoelectrical activity in fasting state. The protocol co nsisted of a 30-min baseline recording, a 30-min recording during anal-side balloon distension located 5 cm distal to the most distal pair of electrod es, and another 30-min recording after distension. The second session was d esigned to investigate the effect of oral-side distension with the balloon 5 cm proximal to the most proximal pair of electrodes. Jejunal slow waves w ere severely impaired by both anal- and oral-side distension. The dominant power was significantly reduced from -2.96 +/- 0.90 dB at baseline to -6.00 +/- 0.64 dB during anal-side distension (P < 0.0005) and from -3.90 +/- 0. 85 dB at baseline to -7.17 +/- 0.90 dB during oral-side distension (P < 0.0 01). The percentage of normal 17 to 22-cpm slow waves was significantly dec reased from 97.39 +/- 0.88% to 83.48 +/- 3.12% during anal-side distension (P < 0.0005) and from 92.49 +/- 2.42% to 68.80 +/- 7.24% during oral-side d istension (P < 0.002). The percentage of slow wave coupling was decreased f rom 95.08 +/- 2.27% to 52.48 +/- 7.73% during anal-side distension (P < 0.0 005) and from 84.82 +/- 6.75% to 49.21 +/- 8.91% during oral-side distensio n (P < 0.001). The instability coefficient of the dominant frequency was si gnificantly increased during anal-side distension. In conclusion, intralumi nal distension of the jejunum severely impairs jejunal slow waves. The slow waves on both sides of distension become less coupled, less regular, and a re of lower amplitude.