Entrance of Tetrahydropterin Derivatives in Brain after Peripheral Administration: Effect on Biogenic Amine Metabolism’

The ability of various structural analogs of tetrahydrobioptenn to enter the rat brain and remain in the reduced form after i.p. administration was tested because tetrahydrobioptenn itself en-ters poorly. The total content of various pterins in different brain areas was measured by high-pressure liquid chromatography-fluorescence detection, whereas hgh-pressurebquid chromatog-raphy-electrochemical detection was used to measure the con-tent of reduced pterins. The effect of injection of certain tetra-hydropterins on brain content of biogenic amines and their major metabolites was also monitored. In general, when the position 6 side-chain of tetrahydrobiopterin was made shorter and smaller in size, entrance into the brain from the periphery was markedly enhanced. Increasing the lipophilicity or size of the position 6 side-chain did not allow for better entry into brain and, in som