臨床神経学

第48回日本神経学会総会

<シンポジウム2-4>神経伝達機能イメージング:Cutting Edge
ドパミン神経伝達機能マッピング

澤本 伸克

京都大学医学研究科附属高次脳機能総合研究センター〔〒606-8507 京都市左京区聖護院川原町54〕
京都大学ナノメディシン融合教育ユニット

Patients with Parkinson's disease (PD) are impaired when performing cognitive tasks such as mental operations and working memory paradigms, which engage frontal lobe regions. These impairments may reflect degeneration of either nigrostriatal or mesocortical dopaminergic projections. D2 receptor antagonist 11C-raclopride (RAC) with positron emission tomography (PET) now provides an in vivo approach for investigating dopaminergic transmission by monitoring changes in synaptic dopamine levels during task performance. Our RAC PET study suggests that the capacity to release dopamine during a working memory task is impaired in the striatum but relatively preserved in the medial prefrontal cortex in patients with PD. This pattern of dopamine release is in accordance with our previous H215O PET findings showing hypoactivity of the striatum during a mental operation task in PD. These PET findings support a view that degeneration of nigrostriatal dopaminergic projection causing disruption of the cortico-basal ganglia circuit contributes to the cognitive impairments observed in PD. The findings also implicates that mesocortical dopaminergic function may be preserved in PD. Since excessive stimulation of dopamine receptors in the frontal cortex can rather deteriorate its function, the benefit in the striatum and the risk in the frontal cortex should be properly evaluated for dopamine replacement therapy.

(臨床神経, 47:832−834, 2007)
key words:11C-ラクロプライド, ポジトロン断層法(PET), パーキンソン病, 認知障害

(受付日:2007年5月16日)