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Equilibrium striatal:cerebellar 11C-raclopride(RAC)uptake ratios reflect the density of striatal dopamine D2 binding sites.Using positron emission tomographic scanning we have measured striatal RAC uptake in 6 untreated patients with Pakinson's disease(PD),5 chronically treated patients with PD and a fluctuating response to L-dopa,10 patients with striatonigral degeneration(SND),and 9 patients with progressive supranuclear palsy(PSP). Regional cerebral blood flow was determined also,with C15O2.Mean striatal: cerebellar RAC uptake wasnot significantly different from normal in untreated patients with PD,though 2 of these 6 patients showed significantly increased putamen tracer binding.Mean caudate and putamen: cerebellar RAC uptake ratios of the group with PD and a fluctuating response to L-dopa were significantly reduced by 30%and 18%,respectively. The patients with SND had lesser,but significant,10%and 11%decreases in mean caudate and putamen:cerebellar RAC uptake ratios,repsectively,whereas patients with PSP showed 24%and 9%reductions in caudate and putamen: cerebellar RAC binding.Striatal and frontal blood flow were significantly reduced in patients with PSP,but not in patients with PD,but reduced in patients with PD and a fluctuating response to L-dopa.Patients with SND and PSP show a decrease in striatal RAC binding,but to a lesser extent than patients with PD and a fluctuating response to treatment.Failure of patients with SND and PSP to respond well to L-dopa cannot therefore be due to loss of striatal D2 sites alone,but must reflect loss of other basal ganglia connections. |
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CAT scan CAT scan,emission CAT scan,emission,abnormal dopamine receptor dopamine receptor,D2 Parkinson disease progressive supranuclear palsy striatonigral degeneration
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