[18F]Fluoro-Dopa for the in vivo Investigation of Intracerebral Dopamine Metabolism

Although a deficiency of dopamine in the nigrostriatal tracts is known to be associated with Parkinson’s disease (Hornykiewicz, 1966) and the dopamine hypothesis of schizophrenia has been extant for some years, there is still no method by which direct measurements of intracerebral dopamine metabolism can be made during life. Indirect assessments of intracerebral catecholamine metabolism, based on examination of the cerebrospinal fluid have been reported (Van Praag and Korf, 1975). However the cephalad to caudad concentration gradient of amine metabolites in the cerebrospinal fluid and the need to block their reabsorption by the weak organic acid probenecid renders such measurements of limited value. Attempts to measure intracerebral dopamine metabolism based on a knowledge of the veno arterial concentration difference across the brain have not been successful because the amount of metabolites released from the brain are small (Fyro, Settergren and Sedvall, 1975). In our laboratory we have taken a different approach to the problem. We have measured the rate of change of concentration of 18F-fluorine in the brain after an intravenous injection of [18F]5-fluoro dopa and have derived values for intracerebral dopamine metabolism from this information.