Figure 4.

Activation of voltage-gated calcium channels can mimic the intracellular Ca²⁺ elevations induced by NMDA. (a–d) Traces show mean changes in intracellular Ca²⁺ (black line) measured in individual neurons (gray lines) loaded with the high-affinity Ca²⁺ indicator Fura-2. For clarity only every other obtained trace is shown. Arrows mark addition of either 100 µM NMDA or 50 mM KCl + 500 nM Bay K8644. Where indicated, the Ca²⁺ concentration in the medium was increased to 5 mM. The intracellular Ca²⁺ rise induced by NMDA is blocked by 100 µM 7CK (c), and in the presence of 7CK the addition of KCl + Bay K8644 reconstitutes the Ca²⁺ increase (d). (e) Panel shows the aggregate intracellular peak Ca²⁺ elevations as measured by Fura-2. Note the mean Ca²⁺ elevation induced by 50 mM KCl + Bay K8644 in 5 mM Ca²⁺ medium does not exceed that induced by NMDA. Values from each of n = 4 independent experiments are expressed relative to the control (no NMDA) condition. Data are means + s.e.m.; *p < 0.05 vs control.