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 m1 subtype of muscarinic cholinergic receptor in the rat hippocampus following transient global ischemia. This receptor represents the dominant phosphoinositide linked muscarinic receptor in the hippocampus, and is recognized to modulate various aspects of neuronal activity in the hippocampus. Our results demonstrate that following severe transient global ischemia, m1 receptor expression is altered in the hippocampus in a time dependent manner. Expression levels declined in the dentate gyrus within 3 h of insult, reached minimal levels by 6 h, and then slowly recover to control levels. Expression levels in the CA1 and CA3 decreased as well, but did not reach minimal levels until 24 h post-insult. By day 3, expression levels in all regions except CA1, where vulnerable neurons began to drop out, had returned to control levels. These results demonstrate:that transient alterations in the gene expression levels for the m1 muscarinic receptor occur in all subfields of the hippocampus following transient forebrain ischemia.