P2RX3 and ulcerative colitis: Notably, some of the earlier publications on BON provided fundamental knowledge about mechanisms regulating EC cell function, i.e., mechanosensation (Kim et al., 2001a), glucose stimulation of 5-HT release (Kim et al., 2001b), purinergic autocrine regulation of 5-HT release in EC cells (Christofi et al., 2004a), and more recent studies on purinergic P2Y1, P2X3 and P2Y12 regulation of 5-HT release, also showing that P2X3 expression in native EC cells is severely down regulated in ulcerative colitis (Liñán-Rico et al., 2013).