CEREBRAL-ISCHEMIA ALTERS THE REGIONAL HIPPOCAMPAL EXPRESSION OF THE RAT M1 MUSCARINIC ACETYLCHOLINE-RECEPTOR GENE

We investigated the dynamics of the gene expression of the ml subtype of muscarinic cholinergic receptor in the rat hippocampus following tr ansient global ischemia. This receptor represents the dominant phospho inositide linked muscarinic receptor in the hippocampus, and is recogn ized to modulate various aspects of neuronal activity in the hippocamp us. Our results demonstrate that following severe transient global isc hemia, ml receptor expression is altered in the hippocampus in a time dependent manner. Expression levels declined in the dentate gyrus with in 3 h of insult, reached minimal levels by 6 h, and then slowly recov er to control levels. Expression levels in the CA1 and CA3 decreased a s well, but did not reach minimal levels until 24 h post-insult. By da y 3, expression levels in all regions except CA1, where vulnerable neu rons began to drop out, had returned to control levels, These results demonstrate that transient alterations in the gene expression levels f or the ml muscarinic receptor occur in ml subfields of the hippocampus following transient forebrain ischemia.