Figure 4.

FK-506, a potent and specific CN inhibitor, prolongs NMDA channel openings in a CA1 pyramidal cell but not in an interneuron. Representative traces (Left), with openings depicted as downward deflections, and open time histograms (Right) calculated from the same patches before and after application of FK-506 (50–100 nM). Scale bars denote 10 ms and 2 pA. Within 6–8 min after bath application of the drug, the mean open time increased from 1.45 ms to 2.96 ms in this pyramidal cell. In contrast to hippocampal principal cells (also see Table 1), the mean NMDA channel open time in the interneuron did not change during the same experimental conditions. The logarithmic binned open time distributions plotted on a square root ordinate were best fitted with the sum of two exponentials and yielded mean open times of 0.69 ms under control conditions and 0.71 ms in FK-506. The individual open time components (τ₁ and τ₂) are indicated on the graphs with their respective amplitude components in parentheses.