Experimental protein and energy deficiencies: effects on brain free amino acid composition in rats.

1. The effects of protein-energy malnutrition on brain free amino acids of acidic and neutral groups were investigated in experimental rats. 2. Severe energy restriction did not modify the free amino acid composition of the brain while protein deficiency affected certain amino acids of the brain in opposite directions. Significant decreases in the levels of aspartic acid, threonine and tyrosine were observed in the protein-deficient rats. 3. These changes in brain amino acids appear to be specific to protein deficiency and not affected by energy deficiency.