The third major subtype of LGIC is the P2X purinergic receptor subclass. P2X receptors are trimeric (Mio et al. 2005) with each subunit containing an N-terminal ligand binding domain, two membrane-spanning domains linked by an extracellular ligand binding domain, and a C-terminal intracellular domain of moderate length. The second membrane-spanning domain appears to serve as the lining for the ion conduction pathway. EtOH inhibits the function of most P2X receptor subtypes, with some effects reported at concentrations associated with intoxication (Davies et al. 2002; Li et al. 1993). The P2X4 receptor appears to be the most sensitive to inhibition by EtOH, while P2X3 receptors exhibit EtOH-induced potentiation (Davies et al. 2002, 2005). At present, the physiologic consequences of P2X inhibition are unclear.
