Effects of ischemia on regional ligand binding to adrenoceptors in the rat brain.
Changes in ligand binding to adrenoceptors ([3H]prazosin to alpha 1-receptors, [3H]idazoxan to alpha 2-receptors and [125I]cyanopindolol to beta-receptors) following transient cerebral ischemia were investigated using autoradiographic methods. The binding was quantified in brain sections from control rats, rats subjected to 15 min of 2-vessel occlusion ischemia, and rats with recirculation times of 1 h, 1 week or 4 weeks after ischemia. No significant change in alpha 1-receptor binding was observed during and immediately following ischemia, but a decrease was noted in the vulnerable hippocampal CA1 region following 1 week's survival. In the parietal cortex, the ligand binding to alpha 1-receptors increased at 4 weeks. A reduced [3H]idazoxan binding was observed 1 h after ischemia in the temporal cortex and amygdala. No change in ligand binding to beta-receptors was seen in the early phase postischemia, but a marked increase had occurred in the hippocampal CA1 region at 1 and 4 weeks after ischemia (+163% and +142%, respectively), presumably due to accumulation of macrophages expressing beta-receptors. The early postischemic changes in receptor binding may represent downregulation of the adrenoceptors by processes activated during ischemia, while neuronal degeneration, compensatory mechanisms in surviving neurons and proliferation of non-neuronal cells may account for the subsequent changes.
Department of Anesthesiology, University of Lund, University Hospital, Sweden.
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Gustafson
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EJ
Westerberg
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Wieloch
D000319:Adrenergic beta-Antagonists / Q000378:metabolism; D000818:Animals; D001345:Autoradiography; D001921:Brain / Q000098:blood supply / Q000378:metabolism*; D004146:Dioxanes / Q000378:metabolism; D019329:Idazoxan; D002546:Ischemic Attack, Transient / Q000378:metabolism* / Q000503:physiopathology; D008297:Male; D010869:Pindolol / Q000031:analogs & derivatives / Q000378:metabolism; D011224:Prazosin / Q000378:metabolism; D011869:Radioligand Assay; D051381:Rats; D017208:Rats, Wistar; D011941:Receptors, Adrenergic / Q000378:metabolism*; D013997:Time Factors
D000319:Adrenergic beta-Antagonists; D004146:Dioxanes; D011941:Receptors, Adrenergic; C047975:cyanopindolol; D010869:Pindolol; D011224:Prazosin; D019329:Idazoxan