Retarded learning induced by intracerebral administration of amino acids in the neonatal chick

In newly hatched chicks retarded learning develops following intracerebral injections of cycloheximide and is manifest at times well after the drug is no longer acting. Intracerebral administration of amino acid mixtures containing the putative central transmitters glutamate, aspartate and γ-aminobutyric acid and taurine is also effective in producing birds showing retarded learning. The critical period for the effectiveness of these amino acids in producing retardation is the same as for cycloheximide. Intracerebral cycloheximide was shown to result in increased brain concentrations of glutamate and aspartate but not of γ-aminobutyrate or taurine.It is suggested that the accumulation of the two putative excitatory transmitters (glutamate and aspartate) in the developing chick brain prior to the establishment of the blood brain barrier may underlie the retarded learning produced by cycloheximide.