Amino Acid Imbalance and Diet Preference in the Hypothalamic–Hyperphagic Rat

Diet selection by control and hypothalamic–hyperphagic rats was recorded to examine the hypothesis that the plasma amino acid pattern may act as a satiety signal with respect to the decreased food intake associated with amino acid unbalanced diets. Rats were offered choices between: (a) protein-free and imbalanced diets; (b) imbalanced and corrected diets; (c) corrected and basal diets. Although selection by control and operated rats differed with respect to choice a, selection behaviors were comparable for choices b and c. Plasma amino acid patterns were similar in control and operated rats indicating that the same potential satiety signal was present in both groups. Since the "satiety center" was ablated in operated rats, it would seem that if plasma amino acid patterns serve as a satiety signal, this signal must act in some manner other than on the ventromedial area of the hypothalamus.