NEUROTRANSMITTER AND MONOAMINERGIC AMINO-ACID PRECURSOR LEVELS IN RAT-BRAIN - EFFECTS OF CHRONIC-RENAL-FAILURE AND OF MALNUTRITION

Effects of chronic renal failure on brain neurotransmitters (dopamine, norepinephrine, serotonin and histamine) and on monoaminergic amino a cid precursors (tyrosine, phenylalanine and histidine) were investigat ed. To eliminate the consequences of uremia-induced restriction of foo d intake, rats with malnutrition (pair-fed animals) were also studied and both were compared with control rats fed ad libitum. Malnutrition of a moderate degree (food intake 84% of controls) had no effect on am ino acid concentrations in plasma and brain or on neurotransmitter lev els in brain. Concerning plasma amino acids in chronic renal failure a lowered tyrosine level was found resulting in a diminished tyr/phe ra tio. In brain tissue, the tyr/phe ratio was found to be normal, becaus e brain tyrosine levels in chronic renal failure were similar to contr ols. Histidine, which was normal in plasma at this degree of chronic r enal failure, was found to be significantly enhanced in brain in uremi a. Also the neurotransmitters studied were found to be elevated in bra in of chronic uremia, depending on the stage of renal insufficiency.