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February 1968

Electroencephalographic Effects of L-Phenylalanine in the Cat

Author Affiliations

From Department of Neurology, New England Medical Center Hospitals and Tufts University School of Medicine, Boston; and Research Department, Walter E. Fernald State School, Waverly, Mass.

Arch Neurol. 1968;18(2):191-195. doi:10.1001/archneur.1968.00470320093009

THE inherited biochemical defect of the inability to oxidize phenylalanine to tyrosine and the consequent elevation of phenylalanine levels in blood and urine has long been known in phenylketonuria.1 However, the pathogenetic mechanisms of the cerebral abnormality are as yet unclear. The abnormal metabolites of phenylalanine in phenylketonuria have been shown in vitro to inhibit the enzymes dihydroxyphenylalanine (DOPA), 5-hydroxytryptophan, and glutamic acid decarboxylases.2-5 Christensen6 suggested that high levels of one or more amino acids have the effect of preventing the cell from capturing other amino acids or utilizing them. Phenylalanine has been demonstrated in vivo to interfere with the intracellular accumulation of tyrosine.7 Others have described structural defects of myelin in the brains of phenylketonuric patients.8-11 and the lowering of the cerebroside content of the white matter.12

The chronic effects of 1-phenylalanine on the central nervous system have been studied experimentally. Retardation

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