Fig. 1.

Estimation of the AMPA-receptor channel noise. A, The postsynaptic principal neuron was whole-cell-clamped at −80 mV. Extracellular solution contained CTZ (100 μm), and S-AMPA (100 μm) was applied to the cell locally by a puffer pipette, and the induced current was recorded (top). After bandpass filtering, we calculated the variance and smoothed it by a gliding window (bottom). B, Variance was plotted against the amplitude of the (unfiltered) AMPA-induced current. From this relationship, an apparent single-channel AMPA current was estimated by linear regression. See Figure 2 for the definition of variance units.