Postischemic alteration of muscarinic acetylcholine and adenosine A₁ binding sites in gerbil brain

Summary

We studied the alterations in the binding of muscarinic cholinergic and adenosine A₁ receptors following transient cerebral ischemia in Mongolian gerbils and examined the effects of the novel vinca alkaloid derivative vinconate and pentobarbital against the alterations in the binding of these receptors. Animals were allowed to survive for 5 h and 7 days after 10 min of cerebral ischemia induced by bilateral occlusion of common carotid arteries. [³H]Quinuclidinyl benzilate (QNB) and [³H]cyclohexyladenosine (CHA) were used to label muscarinic cholinergic and adenosine A₁ receptors, respectively. The [³H]QNB and [³H]CHA bindings showed no significant alteration in the gerbil brain 5 h after ischemia. However, these bindings in the striatium, the hippocampal CA1 sector, and the hippocampal CA3 sector revealed a significant reduction 7 days after ischemia. The [³H]CHA binding also showed a significant decline in the dentate molecular layer 7 days after ischemia. Intraperitoneal application of vinconate (100 and 300 mg/kg) 10 min and pentobarbital (40 mg/kg) 30 min before ischemia showed a mild reduction in the [³H]CHA binding in the brain 5 h after ischemia. Especially, the reduction was found in the hippocampal CA1 sector and the dentate molecular layer. However, the [³H]QNB binding revealed no significant alteration in the brain 5 h after ischemia. Seven days after ischemia, both drugs prevented a marked reduction in the [³H]CHA binding in the striatium, but not in the hippocampal CA1 sector, the hippocampal CA3 sector, and the dentate molecular layer. By contrast, vinconate and pentobarbital failed to prevent the reduction in the [³H]QNB binding in the striatum. Morphological study indicated that vinconate and pentobarbital ameliorated the neuronal damage to the striatum, but not the hippocampal damage 7 days after ischemia. This histological finding was relatively consistent with the alteration in the [³H]CHA binding. these receptor autoradiographic and histological data suggest that vinconate and pentobarbital can protect the brain from both cellular and functional consequences of ischemia. These findings are of interest in relation to the mechanisms of ischemic brain damage.