Effect of amygdaloid lesions on dietary intake of disproportionate amounts of amino acids

Male rats with bilateral electrolytic lesions in the anterior, medial or posterior aspects of the ventral amygdala and groups of intact rats were fed, in turn, basal, imbalanced or deficient amino acid diets involving threonine or isoleucine as the limiting amino acid, and then a low protein (6% casein) followed by a high protein (75% casein) diet. No change in food intake was observed in animals fed the threonine basal diet postoperatively. When the threonine or isoleucine imbalanced diet was substituted for the respective basal diet, animals with lesions in certain areas of the medial amygdala showed little or no depression in food intake of the imbalanced diets, while all other rats with amygdala lesions reduced their food intake markedly, as did intact controls, when fed such diets. All animals, however, curtailed their food intake of the deficient or high protein diets. The lack of responsiveness of the animals with medial amygdaloid lesions to the imbalanced diets suggests that these areas may be involved in a system regulating food intake of animals fed diets containing imbalanced amino acid mixtures.