Ishida Y, Kawai K, Magata Y, Takeda R, Hashiguchi H, Abe H, Mukai T, Saji H.
Department of Psychiatry, Miyazaki Medical College, University of Miyazaki, Miyazaki, Japan.
We studied tracer distributions in positron emission tomography of ligands for dopamine D1 receptors ([11C]SCH23390) and D2 receptors ([11C]raclopride) and the dopamine precursor analog 6-[18F]fluoro-L-3,4-dihydroxyphenylalanine ([18F]FDOPA), as a measurement of presynaptic dopaminergic function, in the brain after 6-hydroxydopamine lesioning of the medial forebrain bundle in rats. The unilateral lesions were confirmed behaviorally by methamphetamine-induced rotation 2 weeks after lesioning, and the brains were analyzed by tissue dissection following an intravenous bolus of each tracer 3 weeks after lesioning. [11C]Raclopride, but not [11C]SCH23390, showed a higher accumulation in the striatum on the lesion side compared with that on the non-lesioned (intact) side. On the other hand, a lower accumulation of [18F]FDOPA was found in the striatum and cerebral cortex on the lesion side. Our studies demonstrate upregulation of dopamine D2 receptors in the striatum and a decrease in FDOPA uptake in both the striatum and cerebral cortex ipsilateral to the 6-hydroxydopamine lesions. Therefore, the combination of a D2 antagonist and FDOPA may provide a potentially useful method for assessing the effects of dopamine depletion in Parkinson's disease. Copyright 2004 S. Karger AG, Basel.
Neurodegener Dis. 2004;1(2-3):109-12.