We measured in vivo dopaminergic receptor binding usingpositron emission tomography and 18F-spiperone in an untreated symptomatic subject with MPTP-induced parkinsonism. Our technique determines four variables related to entry of 18F-spiperone into brain tissue and subsequent binding to receptors: (1) the combined forward-rate constant k1′ (equal to the product of the maximum number of available specific binding sites, Bmax, times the association rate constant [ka] of 18F-spiperone and receptor); (2) the binding site dissociation rate constant k-1; (3) the free fraction of radioligand not specifically bound in brain tissue, f2; and (4) the regional permeability-surface-area product (PS) of the blood-brain barrier for spiperone. PS and f2 in the patient were not different from that of 10 normal volunteers, whereas the combined forward-rate constant (left caudate: k1′ = 67.6 sec−1, normal = 0.140 ± 0.056) and the dissociation rate constant (left caudate: k−2 = 0.116 sec-1, normal = 0.000339 ± 0.000149) were elevated. These findings provide potential new insights not only into the pathophysiology of this disease but into the clinical importance of dopamine receptor function as well.

Original languageEnglish
Pages (from-to)1575-1579
Number of pages5
Issue number10
StatePublished - Oct 1987


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