Failure of hepatic infusion of amino acids and/or glucose to inhibit onset of feeding in the deprived dog.

Nine mongrels dogs were fed for only 1 hour/day for 7-8 days and the time of onset of their eating and hourly intakes were recorded. At the end of this period, the hepatic portal vein was cannulated and the polyethylene cannula was exteriorized. Upon recovery to their preoperative food intake, the dogs were infused after a 23 hour fast over a 4 minute period with an amino acid (AA) mixture (FreAmine II, McGaw Laboratories) equal to 7.2% (37 trials), 14.4% (28 trials), or 21.6% (28 trials) of the dogs' daily AA requirements and presented with food 4 minutes later. In all 93 trials the dogs ate within 30 seconds of presentation of food and their hourly intakes were not significantly different from isotonic saline infusions. Six 23 hour deprived dogs were infused with 21.6% of their AA requirement and then presented with food 11 minutes later. Again, these dogs began eating within 30 seconds of presentation of food. Finally, 4 dogs were infused over a 4 minute period after a 23 hour fast (12 trials) with 7.2% of their daily AA requirements mixed with 6 g of glucose and presented with food 4 minutes later. The dogs began eating within 30 seconds in all 12 trials and their hourly intakes were not significantly depressed. These results question the existence or role of hepatic glucoammonium receptors involved in the control of feeding behavior.