The muscarinic acetylcholine receptor M2, also known as the cholinergic receptor, muscarinic 2, is a muscarinic acetylcholine receptor. The M2 muscarinic receptors are located in the heart, where they act to slow the heart rate down to normal sinus rhythm after stimulatory actions of the sympathetic nervous system, by slowing the speed of depolarization. The CHRM2 gene inhibits the release of acetylcholine from cholinergic fibers in the lungs and elsewhere. In airway parasympathetic neurons, it is decreased by viral infections and by interferon-gamma, increasing actylcholine release. This gene is thought to be involved in neuronal excitability, synaptic plasticity and feedback regulation of acetylcholine release and has previously been implicated in higher cognitive processing. In a sample of 667 individuals from 304 families, Gosso MF et al. genotyped three single-nucleotide polymorphisms (SNPs) in the CHRM2 gene on 7q31-35. CHRM2 is implicated in memory and cognition, functions impaired in many neuropsychiatric disorders. Wang et al. evidence of common and specific genetic effects: association of the muscarinic acetylcholine receptor M2 (CHRM2) gene with alcohol dependence and major depressive syndrome.