Figure 6. The effect of Cd²⁺, nifedipine, and efonidipine on spontaneous burst and spiking discharges in acute STN slices.

Scale bar: 2 seconds. 10 μM nifedipine (A) and 50 μM Cd²⁺ (B) show little inhibition on spontaneous firing of STN. (C) Efonidipine changes the spontaneous burst to spiking discharges in a concentration-dependent manner (left panel). On the other hand, the spontaneous spiking discharges are not affected by the same concentrations of efonidipine (right). The bottom right traces show manifest inhibition of LVA Ca²⁺ currents (elicited at –40 mV from a holding potential of –120 mV) by 20 μM efonidipine (n = 4). Scale bars: 50 pA/20 ms. The data in the boxed panel show that 20 μM efonidipine has little effect on subthalamic Na⁺ currents that are elicited either at 0 mV (upper panel) or at –40 mV (lower panel; the experimental conditions are the same as those described in Figure 2B). Scale bars: 500 pA/1 ms.