—High circulating levels of phenylalanine caused depletions of threonine, valine, methionine, isoleucine, leucine, histidine, tryptophan, and tyrosine in immature and adult rat brains. The branched‐chain amino acids were most affected. Their reductions ranged between 38–64 per cent of control values when phenylalanine was administered either parenterally or in the diet. The pattern of cerebral amino acid depletions found in phenylalanine‐injected infant rats was similar to that of the adults. Phenylalanine loading caused depletions in serum amino acid levels in adult rats, but in infant rats the serum levels were either unchanged or somewhat elevated. Tyrosine, when administered to adult rats either parenterally or via the diet, caused cerebral depletions in essential amino acids, but the depletions were not as striking as with phenylalanine. In both the infant and adult rat, brain‐blood ratios of most of the essential amino acids were significantly reduced by phenylalanine loading.

817crease in liver L-a-glycerophosphate concentration and in incorporation of intravenously injected palmitic acid-l-C14 into liver triglycerides. It is suggested that these metabolic alterations may play an important role in the pathogenesis of fatty liver and of hypertriglyceridemia produced by ethanol. The ,changes could be observed only during the first few hours following ingestion of ethanol.It has been established in this laboratory that certain conditions of dietary intake of excessive phenylalanine by rats ( 1 ) or monkeys(2) result in urinary excretion of phenylketones and elevated blood phenylalanine levels. Since it has been shown that phenylketonuric monkeys have severe and presumably permanent decrements in learning abilities and other complex behaviors(2), it was of interest to determine if rats with similar biochemical evidence of phenylketonuria also *Supported by U. S. Public Health Service grant.have deficits in higher-order behavior. This preliminary report describes a behavioral testing procedure which has been reliable in rapidly detecting and quantifying a decrement in the maze performance of phenylketonuric rats.The selection of this procedure was dictated in part by several previous experiments which may be described briefly. The initial goal of this research has been to devise a learning task simple enough for rapid mastery by the rat, but difficult enough for reby guest on July 26, 2015 ebm.sagepub.com Downloaded from

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