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.