Effects of glycine-mediated NMDA receptor activation on PM insertion of pHluorin-GluR-A. A, plot of normalized amplitude of the fast quenching phase during the pH test. The plot shows averaged data (black circles with error bars) overlaid with individual data points (grey circles) from 6 cells. No statistically significant differences between time points were observed (P > 0.05), indicating that the PM-inserted receptor fraction was stable over at least 30 minutes under control conditions. B, a pair of representative traces of pHluorin-GluR-A fluorescence obtained with a 30 min interval under control conditions. C, averaged data plot (n = 8 cells) showing glycine-induced long-lasting changes in the fast quenching phase amplitude. Thirty minutes after the start of a brief (5 minute; horizontal bar) application of the glycine/0 Mg2+ solution, the fast phase amplitude significantly increased compared to non-treated cells (P < 0.01) indicating persistent insertion of additional pHluorin-GluR-A receptors in the PM. D, typical traces showing glycine-induced increase in the fast phase of fluorescence quenching, as well as a rise in the baseline fluorescence. Both effects are consistent with an increase in the PM-inserted fraction of pHluorin-GluR-A receptors.