Reduction of food intake by intestinal macronutrient infusion is not reversed by NMDA receptor blockade

Rats increase their intake of food, but not water, after intraperitoneal in jection of MK-801, a noncompetitive antagonist of N-methyl-D-aspartate-acti vated ion channels. We hypoth esized that MK-801 might enhance intake by in terfering with intestinal chemosensory signals. To test this hypothesis, we examined the effect of the antagonist on 15% sucrose intake after an: intr aduodenal infusion of maltotriose, oleic acid, or phenylalanine in both rea l- and sham-feeding paradigms. MK-801 (100 mu g/kg) significantly increased sucrose intake regardless of the composition of the infusate during real f eeding. Furthermore, MK-801 had no effect on reduction of sucrose intake by intestinal nutrient infusions in sham-feeding rats. These results indicate that MK-801 does not increase meal size and duration by interfering with s ignals activated by intestinal macronutrients.