Hepatic-portal nutrient infustion: effect on feeding in intact and vagotomized rabbits.

Hepatic-portal infusions of isotonic glucose did not influence food intake in free-feeding rabbits. In contrast, several other macronutrients and some of their metabolites, infused via the same route, cause anorexia followed by prolonged hypophagia. Its duration was generally decreased when the same infusions were performed during the nocturnal period. Vagotomy did not significantly alter the food intake responses to hepatic-portal infusions of either glucose or the other experimental substances. The results of related experiments have demonstrated that prolonged anorexia was not a consequence of the fast infusion rate or the generalized behavioral mallaise. However, when the infusions of most anorexigenic substances were followed by intraperitoneal administration of insulin, the duration of anorexia was shortened and food consumption was elevated. The results provided indirect evidence for the vagally mediated regulatory contribution of the previously studied neural and humoral intestinal mechanisms which are bypassed by infusing nutrient loads directly into the hepatic-portal circulation.