Figure 1.
Enhancement of NMDA channel gating induced by the activation of remote NMDA receptors. A, The recording configuration used to investigate the effects of remote NMDA receptor activation by the bath application of the NMDA receptor agonist l-aspartate on the NMDA channel within the membrane patch. B, A record of NMDA single-channel open probability (Po; bin, 10 sec) before and during stimulation of remote NMDA receptors by the bath application of the NMDA receptor agonist l-aspartate (500 μm). The break during the recording was required for adjusting the patch potential to 70 mV from the NMDA channel reversal potential after l-aspartate was applied to neurons. C, The average single-channel open probability (bin, 10 sec; 7 patches) normalized by the mean values of Po before l-aspartate application. D, The graph shows the I-V relationship for single-channel currents before (open circles) and during l-aspartate application (filled circles). The lines that are depicted represent least-squares regression lines. E, Dwell-time histograms of open and shut times were compiled before (top), during (middle), and after (bottom) the bath application of l-aspartate. In the dwell-time histograms, the solid line shows the Marquardt least-squares fit for the histogram, the dashed lines indicate individual exponential components, and n is the number of events. There were three open components and five closing components.τ, Time constant; percentage values indicate relative areas of each component. F, Representative single-channel current traces are illustrated before, during, and after the application of l-aspartate. o, Open level; c, closed level. G, Summarized data (mean ± SEM) showing that increases in the concentration of l-aspartate applied to remote NMDA receptors increased the Po and mean open time (to) of recorded NMDA channels. Values in parentheses indicate the number of patches tested; *p < 0.05, Wilcoxon test.