Figure 5.
NMDA, but not AMPA, conductances engage a high-frequency, action potential-independent oscillation. A, Dynamic clamp experiments performed in the presence of TTX and recorded in the whole-cell configuration. Top, Example electrical trace obtained for [Mg2+]o = 0.0 mm with the injected current below. Just before the conductance step, a low-frequency oscillation can be seen. During the conductance step the membrane voltage remains flat. Bottom, Same as top except [Mg2+]o = 1.5 mm. During the conductance step a higher-frequency oscillation (relative to that before the step) is observed. Below each voltage trace is the injected current waveform. B, Control firing evoked by applying the same NMDA conductance step ([Mg2+]o = 1.5) as in A, before applying TTX.