We investigated postischemic alterations in
benzodiazepine receptor, D1
dopamine receptor, and
muscarinic acetylcholine receptor binding after transient middle cerebral artery (MCA) occlusion in rats using [3H]-
flumazenil, [3H]-
SCH23390, and [3H]-N-methyl-4-piperidyl benzilate ([3H]-NMPB), respectively, as radioligand. These
ligand bindings were determined at 3 and 24 h and at 3 and 7 days after
ischemia/reperfusion of MCA by using autoradiographic methods. Ischemic cell injury was clearly detected from 3 h after
ischemia/reperfusion and progressively increased from 3-24 h after
ischemia/reperfusion of MCA. The area of cell injury reached maximum at 24 h after
ischemia/reperfusion of MCA. [3H]-
SCH23390 binding was reduced to 47% of the contralateral side at 3 days after
ischemia/reperfusion of MCA. After 7 days, [3H]-
SCH23390 binding was further reduced by 20% in the striatum. [3H]-NMPB binding was slightly decreased in both the striatum and cerebral cortex at 3 days after
ischemia/reperfusion of MCA, and [3H]-NMPB binding in the striatum and cerebral cortex were reduced to 42 and 62% of the contralateral side at 7 days after
ischemia/reperfusion of MCA. [3H]-NMPB was also decreased at 24 h. In contrast, [3H]-
flumazenil binding was not decreased in the striatum and cerebral cortex within 7 days after
ischemia/reperfusion of MCA. These results suggest that [3H]-
SCH23390 and [3H]-NMPB binding do not correlate with cell injury by
ischemia/reperfusion, although vulnerability to
ischemia/reperfusion was observed with these receptors. In addition, central
benzodiazepine receptor imaging might be essentially stable to neuronal cell injury induced by transient focal
cerebral ischemia in rats, in contrast to the results of PET studies.