Intestinointestinal inhibitory reflexes: effect of distension on intestinal slow waves.

The motor response induced by intraluminal distension of the small intestine has been well investigated. However, little is known of the myoelectrical response to intraluminal distension. The aim of this study was to investigate 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 with three pairs of electrodes on the jejunum and an intestinal fistula. The first study session was designed to investigate the effects of anal-side distension on jejunal myoelectrical activity in fasting state. The protocol consisted 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 electrodes, and another 30-min recording after distension. The second session was designed to investigate the effect of oral-side distension with the balloon 5 cm proximal to the most proximal pair of electrodes. Jejunal slow waves were 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 < 0.001). The percentage of normal 17 to 22-cpm slow waves was significantly decreased 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 distension (P < 0.002). The percentage of slow wave coupling was decreased from 95.08 +/- 2.27% to 52.48 +/- 7.73% during anal-side distension (P < 0.0005) and from 84.82 +/- 6.75% to 49.21 +/- 8.91% during oral-side distension (P < 0.001). The instability coefficient of the dominant frequency was significantly increased during anal-side distension. In conclusion, intraluminal distension of the jejunum severely impairs jejunal slow waves. The slow waves on both sides of distension become less coupled, less regular, and are of lower amplitude.