The muscarinic M1 receptor is a membrane protein with seven transmembrane segments and binds with acetylcholine on the extracellular surface. The acetylcholine-bound receptor interacts with and activates G protein Gq/G11. The receptor is found in the hippocampal and cortical regions of the brain as well as in the parasympathetic ganglia. It is involved in many processes, including the initiation of seizures, learning and memory, and regulation of the force and rate of heart contractions. Because of its involvement in these processes, the M1 receptor is a compelling drug target for Alzheimers disease and other neurological and psychiatric disorders.