POSTISCHEMIC ALTERATION OF MUSCARINIC ACETYLCHOLINE, ADENOSINE-A1 AND CALCIUM-ANTAGONIST BINDING-SITES IN SELECTIVELY VULNERABLE AREAS - AN AUTORADIOGRAPHIC STUDY OF GERBIL BRAIN

We performed receptor autoradiography to determine sequential alterations in the binding of muscarinic cholinergic and adenosine A1 receptors and of a voltage dependent L-type calcium channel blocker 1 h-1 month after transient cerebral ischemia in the gerbil brain. [H-3]Quinuclidinyl benzilate (QNB), [H-3]cyclohexyladenosine (CHA) and [H-3]PN200-110 were used to label muscarinic and adenosine A1 receptors and L-type calcium channels, respectively. Transient ischemia was induced for 1 0 min. [H-3]QNB and [H-3]CHA binding showed no significant alteration in selectively vulnerable areas at an early stage (1-24 h) of recirculation. However, the dentate molecular layer which was resistant to ischemia revealed a significant decrease in the [H-3]CHA binding sites 24 h after ischemia. Thereafter, the [H-3]QNB and [H-3]CHA binding showed significant reduction in most of selectively vulnerable areas. Marked reduction was especially found in the dorsolateral part of striatum and the hippocampal CA1 sector which was the most vulnerable to ischemia. In contrast, [H-3]PN200-110 binding showed a transient elevation in the hippocampal CA1 sector, the dentate molecular layer and the thalamus 1 h of recirculation. However, the striatum and neocortex revealed no alteration in the [H-3]PN200-110 binding. Thereafter, the reduction in the [H-3]PN200-110 binding was seen only in the dorsolateral part of the striatum and the hippocampal CA1 sector. The results suggest that transient cerebral ischemia can cause the alterations in the binding of muscarinic cholinergic and adenosine A1 receptors and of L-type calcium channel blocker in most of selectively vulnerable areas. Furthermore, they suggest that the postischemic alteration in the binding of adenosine A1 receptors is, greater than those in the binding of muscarinic cholinergic receptors and of L-type calcium channel blocker.