Up-regulation of P2X7 receptor-immunoreactivity by in vitro ischemia on the plasma membrane of cultured rat cortical neurons.

Mixed neuronal/astrocytic cortical cell cultures of the rat were incubated for 2 or 12h under normoxic or ischemic conditions. Subsequent flow cytometric analysis with an anti-P2X7 receptor antibody directed against an extracellular epitope indicated the up-regulation of these receptors at the plasma membrane by 12h of ischemia. Labelling of MAP-2 immunopositive neurons by an anti-P2X7 antibody directed against a C-terminal epitope, documented the selectivity of the ischemia-induced increase in receptor-density for the neuronal population. By contrast, staining of GFAP immunopositive astrocytes by the same anti-P2X7 antibody excluded any effect of ischemia on the astrocytic density of P2X7 receptors. The ischemic up-regulation of neuronal P2X7 receptors is in perfect agreement with the previously reported facilitation of transmitter release from the GABAergic non-pyramidal cell type in such cultures [K. Wirkner, A. Köfalvi, W. Fischer, A. Günther, H. Franke, H. Gröger-Arndt, W. Nörenberg, E. Madarasz, E.S. Vizi, D. Schneider, B. Sperlagh, P. Illes, Supersensitivity of P2X7 receptors in cerebrocortical cell cultures after in vitro ischemia, J. Neurochem. 95 (2005) 1421-1437].