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The penetration and distribution in various areas of cat brain of 14C-DL-DOPA and/or its derivatives was studied by the autoradiographic technique. The highest activity was found, 1 hr after administration, in the caudate nucleus, putamen and n. accumbens, while hypothalamus, substantia nigra, substantia grisea pericentralis, tuberculum olfactorium, raphe nuclei and nucleus interpeduncolaris showed lower levels of labelling. Very low activity was detected in the cerebral cortex and in the other gray and white matter structures of brain. After pretreatment with a peripheral DOPA-decarboxylase inhibitor or high dosage of cold DOPA, the distribution pattern was not modified but the levels of radioactivity were greatly enhanced. The localization of the drug in dopaminergic structures and other areas of the brain is discussed.

The distribution of i.v. injected S-adenosyl-L-(methyl-14C) methionine was studied in the whole body of mice and in the cat brain using an autoradiographic technique. The drug was concentrated, at shorter survival times, mainly in the blood stream and in highly vascularized organs. Low concentration of radioactivity was found at longer times in the central nervous system (CNS). The quantitative analysis by means of organ radioassay was carried out in rats and confirmed the autoradiographic data.