P2RX4 and psychiatric disorder: In physio-pathological conditions including neuropathic pain, psychiatric disorders or epileptic seizures, enhanced P2 receptor expression has been reported, such as P2X4 or P2X7 (Tsuda et al., 2003; Beggs et al., 2012; Henshall et al., 2013; Sperlagh and Illes, 2014).