Presynaptic and postsynaptic nigrostriatal dopaminergic functions in multiple system atrophy.

A simultaneous evaluation of presynaptic and postsynaptic dopaminergic positron emission tomography markers, the dopamine transporters and the dopamine D2-like receptors, was performed in eight patients with parkinsonian phenotype of multiple system atrophy. Both presynaptic and postsynaptic markers were revealed to have declined in such a manner that they kept strong positive correlation throughout the striatum of all patients, suggesting that the degeneration process in the striatum may involve the entire structure of the dopaminergic synapse. In two L-3,4,dihydroxyphenyl-alanine-responsive cases, the balance of decline in two markers was relatively shifted to presynaptic dominant side. Correlative positron emission tomography study of presynaptic and postsynaptic dopaminergic function may be useful for the diagnosis of multiple system atrophy and to understand the mechanisms of its temporal L-3,4,dihydroxyphenyl-alanine responsiveness.