2010; Bava and Tapert, 2010; Bava et al., 2009; Squeglia et al., 2009). The cholinergic M2 receptor gene belongs to a family of muscarinic acetylcholine G-protein coupled receptors with five known subtypes (M1–M5). The M2 receptors in the mesolimbic dopaminergic system play a significant role in modulating the level of dopamine release (Picciotto et al., 2012; Scarr, 2012; Cachope et al., 2012; Oldenburg and Ding, 2011; Witten et al., 2010). This has a important effect in governing the reward system (Mark et al., 2011; Shabani et al., 2010), including modulating the effects of alcohol on it (Adermark et al., 2011). M2 receptors also modulate synaptic transmission in cortical circuits affecting the pyramidal neurons (Picciotto et al., 2012).
