Purinergic Signalling (2012) 8 (Suppl 1):S61–S79 glial fibrillary acidic protein (GFAP)-positive astroglia express multiple P2X receptors, predominantly the P2X4, P2X6, and P2X7 (using anti-P2X4 receptor, anti-P2X6 receptor (#APR-013), and anti-P2X7 receptor antibodies) as well as P2Y receptors. Although expressing both P2X and P2Y receptors, it was demonstrated that P2Y1 and P2Y2 receptors are involved in calcium signaling in response to extracellular nucleotides, thereby playing a role in cell-to-cell signaling (Fig. 8) [65]. Lacking specific antagonists to the P2X4 channel, P2X4−/− knockout (KO) mice were used to elucidate the role of P2X4 S73 in hippocampal synaptic transmission. KO of P2X4 was assessed by Western blot analysis [66]. It was demon- strated that P2X4 in wild-type animals affects long-term potentiation, an effect which was abolished in the KO animals [66]. In a study, testing the effect of different external ionic environments on calcium changes and the expression of P2X purinergic receptors in control and cystic fibrosis airway epithelial cells, it was demonstrated that CFBE41o− airway epithelial cells express P2X4, P2X5, as well as P2X6 by immunohistochemical studies using anti-P2X4 receptor, Fig. 8 Localization of P2X receptor subunits on astroglia. Localization of P2X receptors in astroglia was characterized by double immunoflu- orescence staining of P2X1 (A), P2X2 (B), P2X3 (C), P2X4 (D), P2X5 (E), P2X6 (F), P2X7 (G) using their respective Alomone Labs antibodies (Cy3, red) and GFAP (Cy2, yellow green). Strong staining for the P2X1 receptor was detected only in axon-like fibers (A). No clear immuno- reactivity was observed for P2X2 and P2X3 receptor subtypes on astroglia (B, C). P2X4, P2X5, P2X6, P2X7 receptors were found to be expressed (Da, Ec, Fa, Ga). As representative control images are the anti-P2X5 receptor antibody (#APR-005) pre-incubated with its control peptide antigen (Ea) and GFAP fluorescence alone (Ea–d). Adapted from reference 65 with permission of Elsevier