SIMULTANEOUS MEASUREMENT OF [F-18] FDOPA METABOLISM AND CEREBRAL BLOOD-FLOW IN NEWBORN PIGLETS

Available information on the dopamine (DA) metabolism of the immature brain is rare. In order to establish a useful animal model we have per formed PET experiments in anesthetized neonatal pips using 6-[F-18]-fl uoro-L-DOPA (FDOPA) as tracer. In this study, we have simultaneously d etermined the cerebral blood flow and the rare constant of FDOPA conve rsion by the aromatic amino acid decarboxylase, the ultimate enzyme in the synthesis of dopamine. The estimated values of FDOPA decarboxylat ion in the basal ganglia were similar to values calculated in adult an imals and humans. However, in contrast to those studies a significant decarboxylation was also found in the frontal cortex and the cerebellu m HPLC analysis of brain samples also revealed extensive and rapid met abolism of FDOPA in the five investigated brain regions. At 8 min afte r tracer injection about 80% of FDOPA was already converted to FDA and its metabolites. Surprisingly, a rather high fraction (16-21%) of [F- 18]-fluoro-3-metboxytyramine was found which may indicate a low storag e capacity of vesicular DA at this perinatal stage, It is suggested th at the findings are related to the ontogenetic development of the dopa minergic system. The knowledge of the regulation of the DA metabolism in the immature brain may have implications for the understanding of n eurodevelopmental effects of perinatal oxygen deprivation. (C) 1998 IS DN. Published by Elsevier Science Ltd.