Timing and dose of amino acids injected into prepyriform cortex influence food intake

The effects of time before feeding and dose of dietary-limiting amino acids (DLAA) injected into the prepyriform cortex (PPC) on intake of amino acid-imbalanced diets were evaluated. Intake of imbalanced diet was increased from ∼50% to ∼75% of baseline when an optimal amount of DLAA (1 nmol l-isoleucine or 2 nmol l-threonine) was injected immediately prior to feeding. Injections made several hours prior to feeding were more effective, increasing intake of imbalanced diets to ∼85% of baseline. Delivering two half-optimal doses of DLAA,several hours apart, increased intake of imbalanced diet only to the same level as a single injection of the optimal dose immediately prior to feeding. The increase in intake of a threonine-imbalanced diet after injecting 2 nmol threonine 6 h prior to feeding was abolished if an additional 2 nmol threonine was injected immediately prior to feeding. It appears that it is the sum of the changes in tissue DLAA concentrations in the PPC that are recognized and influence food intake when amino acid imbalanced diets are fed.