Suppression of meal size by intestinal nutrients is eliminated by celiac vagal deafferentation

The arrival of nutrients in the gastrointestinal tract suppresses intake. To specify the neural pathways and receptor locations of this feedback, we examined the effects of intraduodenal infusions of 10 nutrients plus saline on short-term food intake of rats with selective deafferentations of vagal celiac branches. Three response profiles were observed: 1) isotonic saline, 5.6% glycerol, and 3% fructose did not inhibit intake of controls or selectively deafferented animals; 2) 3% glucose, 3% maltose, 3% L-phenylalanine, 12% Isocal, and 1.4% oleic acid suppressed intake of controls, but this inhibition was eliminated by vagal celiac deafferentation; and 3) 3% casein hydrolysate and 24% Isocal suppressed intake of controls and rats with selective vagotomies, although the latter exhibited significantly less suppression. In addition, elimination of celiac afferents chronically reduced meal size (i.e., first 30-min intake) without reducing daily food intake or body weight. Furthermore, D-phenylalanine infusions produced a delayed suppression of food intake in controls (possibly from intraluminal irritation); however, this reduction was eliminated with celiac deafferentation. Overall, this experiment indicates that vagal celiac afferents are critical for preabsorptive detection of some energy-yielding molecules or properties of nutrient solutions (as well as, perhaps, intraluminal inflammation), but not others, which are still detected, although only partially.