Fig. 7. Reversal of the NCX during glutamate treatment of cortical neurons.

(a-c) Cortical neurons were wide-field fluorescence imaged to quantify the glutamate-triggered rise of [Ca²⁺]_c with Fura-4F (a) and in separate experiments the rise of [Na⁺]_c (b) and the depolarization of the ΔΨ_P (c), using SBFI and PMPI, respectively. Glutamate (100 μM) plus glycine (10 μM) were applied in the absence of Mg²⁺ with a perfusion system (Glu), and then were washed out with Mg²⁺-containing (1 mM) experimental medium. (d) The thermodynamic driving force of the NCX was calculated from the data shown in (a-c). The [Ca²⁺]_e and [Na⁺]_e were 1.3 mM and 136 mM respectively. A negative ΔG was defined as the forward mode of exchange; i.e. pumping Ca²⁺ out from the cell, while positive ΔG indicates reversal of the NCX. (e) Effect of the reverse-mode NCX inhibitor KB-R7943 (KBR; 10 μM) on the glutamate-triggered [Ca²⁺]_c plateau. Drug application was performed with a perfusion system with nifedipine (1 μM) continuously present in all perfusion lines. Data are mean ± SE of neurons pooled from 6 experiments per condition performed in 3 cell culture preparations (n=385, 202, 202, and 169 for (a), (b), (c), and (d), respectively). The SE in (d) was propagated from (a-c).