Shin-ichi Iwata, Takao Shimizu, Masahiro Nomoto and Takeo Fukuda
Department of Pharmacology, Faculty of Medicine, University of Kagoshima, Kagoshima 890, Japan
Abstract: We measured the number of D1-receptors (Bmax) in the striatum whose dopaminergic terminals were destroyed to various degrees by 6-hydroxydopamine (6-OHDA) to clarify the relationship between the degree of denervation and the change in Bmax for D1-receptor. Rats were sacrificed 28 days after 6-OHDA treatment, and [3H]SCH23390 (R(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro- 1H-3-benzazepine) binding capacity and monoamine content were measured in striatal homogenate. Bmax was significantly upregulated when dopamine content was reduced to less than 5% of that in the vehicle-treated striatum. In contrast, it was significantly decreased when dopamine content was 5 - 25% of that in the vehicle-treated striatum. The D1-receptors showed either upregulation or downregulation depending on the degree of denervation.
[3H]SCH23390, 6-Hydroxydopamine, Upregulation
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