Possible Interaction: Phenylalanine and Serotonin

“ Urinary serotonin fell during phenylalanine loading in six patients.”

“The excess of phenylalanine blocks the transport of important amino acids to the brain contributing to reduced levels of dopamine and serotonin.”

“The potential for pEPA to inhibit selectively and reversibly the biosynthesis of serotonin may contribute to the characterization of the role of serotonin in behavioral and physiological activities.”

“An inhibition of decarboxylase activity by phenylalanine decreases the concentrations of 5-HT and 5-HIAA, a deficiency which is reversible only by dietary measures.”

“Transport of the precursor amino acids from blood into the brain for serotonin and dopamine synthesis is reported to be inhibited by high blood Phe concentrations.”

“Fifteen years later, when early treatment of PKU with a phenylalanine restricted diet was routinely introduced, an inverse relationship was found between phenylalanine levels and the urinary excretion of dopamine and serotonin.”

“Patients with phenylalanine hydroxylase deficiency show increased concentrations of biopterins and neopterins, and reduced concentrations of serotonin and catecholamines, when phenylalanine concentrations are raised.”

“In classical PKU, the serotonin and dopamine biosynthesis is inhibited by high L-phenylalanine in blood and tissues.”

“… phenylalanine … serotonin , catecholamine, or gammaaminobutyric acid syntheses and that a deficiency of one or more of these potential transmitter substances produces neurological symp toms.'-3 Other … in phenylketonuria, once established, is irreversible, a clinical finding that points to the presence of permanent structural alterations within the central nervous system.”

“Tyrosine did not alter dopamine or noradrenaline levels, while phenylalanine lowered dopamine, noradrenaline and serotonin.”