Effect of cerebral ischemia on dopamine receptors and uptake sites in the gerbil hippocampus.
Dopamine D1 and D2 receptors and uptake sites were studied in the gerbil hippocampus, parietal cortex and thalamus 1 h to 7 days after 10 min of cerebral ischemia using the occlusion of bilateral common carotid arteries. [3H]SCH23390 ([N-methyl-3H]R[+]-8-chloro-2,3,4,5-tetrahydro-3-methyl-5-phenyl-7-ol-be nzazepine) and [3H]mazindol were used as markers of dopamine D1 receptors and uptake sites, respectively. [3H]Nemonapride was used to label dopamine D2 receptors. No obvious alteration in [3H]SCH23390 and [3H]mazindol binding was found in the hippocampus up to 48 h after ischemia. These bindings showed a significant reduction in the hippocampus after 7 days of recirculation. In contrast, [3H]nemonapride binding was unaffected in the hippocampus during the recirculation periods. The parietal cortex and thalamus also exhibited no significant changes in [3H]SCH23390, [3H]nemonapride and [3H]mazindol binding after ischemia. MAP2 (microtubule-associated protein 2) immunoreactivity was unchanged in all regions up to 48 h after ischemia. Thereafter, a marked loss of MAP2-immunoreactive neurons was observed in the hippocampal CA1 and CA3 neurons 7 days after recirculation. These findings were consistent with histological observations with cresyl violet staining. Our results demonstrate that dopamine D1 receptors and dopamine uptake sites in the hippocampus are susceptible to cerebral ischemia, whereas dopamine D2 receptors in this region are particularly resistant. Furthermore, these findings suggest that dopamine transmission may not be major factor in producing ischemic hippocampal damage.
Araki
T
T
Department of Neurology, Tohoku University School of Medicine, Sendai, Japan.
Kato
H
H
Shuto
K
K
Fujiwara
T
T
Itoyama
Y
Y
D000818:Animals; D001345:Autoradiography; D002545:Brain Ischemia / Q000378:metabolism* / Q000473:pathology; D050483:Dopamine Plasma Membrane Transport Proteins; D005849:Gerbillinae; D006624:Hippocampus / Q000378:metabolism*; D007150:Immunohistochemistry; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism*; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D017447:Receptors, Dopamine D1 / Q000378:metabolism*; D017448:Receptors, Dopamine D2 / Q000378:metabolism*
D050483:Dopamine Plasma Membrane Transport Proteins; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; D009419:Nerve Tissue Proteins; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2