Reflex changes in intestinal tone: relationship to perception

Using an original technique, we demonstrated a modulation of intestinal tonic muscular activity (intestinal tone) by intestino-intestinal reflexes. In 11 healthy volunteers we quantitated intestinal tone variations as changes in the air volume within a flaccid bag (12 cm long) located in the proximal jejunum and maintained at a constant pressure by an electronic barostat. Validation studies with glucagon showed significant intestinal relaxation (117 +/- 10% delta vol; P less than 0.05). In six healthy volunteers, graded balloon distensions (1 min duration at 10-min intervals in 8-ml stepwise increments) were randomly performed 8 cm orad, 8 cm caudad, and 20 cm caudad to the bag of the barostat. Perception was scored (0-6) by a questionnaire. Distensions at the three sites induced similar perception; at the threshold for discomfort (score greater than or equal to 5) distension also induced intestinal relaxatory responses (43 +/- 10%, 34 +/- 5%, and 32 +/- 4% delta vol from orad to caudad, respectively; P less than 0.05 for all). However, while unperceived orad distensions (13 +/- 2 ml) induced reflex relaxation (21 +/- 6% delta vol; P less than 0.05), 20-cm-caudad distensions at higher levels (16 +/- 2 ml, 2.7 +/- 0.5 perception score; P less than 0.05) did not (1 +/- 7% delta vol). This dissociation between perception and intestinal tone reflexes suggests that both responses to intestinal distension are mediated by specific mechanisms.