Modulation of gastric distension-induced sensations by small intestinal receptors

Duodenal lipid exacerbates gastrointestinal sensations during gastric distension. Using luminal application of the local anesthetic benzocaine, we investigated the role of intestinal receptors in the induction of these sensations. Nine healthy subjects were studied on five occasions, during which isotonic saline or 20% lipid (2 kcal/min), combined with (duodenal or jejunal) 0.75% benzocaine or vehicle at 2.5 ml/min, was infused intraduodenally before and during gastric distension. Intragastric pressures and volumes, gastrointestinal sensations, and plasma CCK levels were determined. Duodenal lipid combined with vehicle increased gastric volume (in ml: saline, −10 ± 18; lipid/vehicle, 237 ± 30) and plasma CCK [mean levels (pmol/l): saline, 2.0 ± 0.2; lipid/vehicle, 8.0 ± 1.6] and, during distensions, induced nausea (scores: saline, 3 ± 2: lipid/vehicle, 58 ± 19) and decreased pressures at which fullness and discomfort occurred. Duodenal but not jejunal benzocaine attenuated the effect of lipid on gastric volume, plasma CCK, and nausea during distension (135 ± 38 and 216 ± 40 ml, 4.6 ± 0.6 pmol/l and not assessed, and 37 ± 12 and 64 ± 21 for lipid + duodenal benzocaine and lipid + jejunal benzocaine, respectively) and on pressures for sensations. In conclusion, intestinal receptors modulate gastrointestinal sensations associated with duodenal lipid and gastric distension. There is also the potential for local neural mechanisms to regulate CCK release and thereby reduce afferent activation indirectly.

Effects of posture on gastric emptying and satiety ratings after a nutritive liquid and solid meal

To study the effects of posture and meal structure on gastric emptying and satiety, nine women ingested tomato soup and then immediately or 20 min later an egg sandwich, when seated and when supine. The lag time was not different, but the half-emptying time of the sandwich was 32% longer ( P < 0.01) and the emptying rate after the lag phase was 39% slower ( P < 0.01) when the subjects were supine than when they were seated. The half-emptying time of the soup was 50% longer ( P < 0.01) when the subjects were supine and ingested the soup immediately before the sandwich than in the other three conditions. Postprandial hunger ratings recovered more slowly ( P < 0.01) when the subjects ingested the soup 20 min before the sandwich than when they ingested the soup immediately before the sandwich. These results suggest that posture did not affect the intragastric distribution of the sandwich but affected propulsion of the meal into the intestine and that postprandial satiety was enhanced by the cumulative effect over time of a 20-min “head start” in stimulation of intestinal receptors by emptying of the soup.