Mitochondrial Ca²⁺ overload induced by AMPA receptor activation is reduced in Bax^−/− oligodendrocytes. A, B, Oligodendrocytes loaded with fura-2 were exposed to AMPA combined with CTZ in the presence of FCCP, and the changes in [Ca²⁺]_i were analyzed by microfluorimetry. Selective activation of AMPA receptors, under these conditions, increased the [Ca²⁺]_i levels in wild-type oligodendrocytes, while this effect was significantly reduced in Bax^+/− and Bax-null oligodendrocytes (**p < 0.0005). C, Effects of FCCP on mitochondrial calcium in oligodendrocytes loaded with Rhod-2 AM. FCCP was used as an internal control to release Ca²⁺ from mitochondria. D, Cells, loaded with Rhod-2 AM, were exposed to AMPA (10 μm) plus CTZ (100 μm) for 30 s. [Ca²⁺]_mit induced by AMPA was reduced in Bax^−/− oligodendrocytes compared with Bax^+/+ control cells. Recordings in D illustrate the average ± SEM responses of 63 cells from at least 5 experiments. E, F, Oligodendrocytes, loaded with Rhod-2-AM, were exposed to continuous application of AMPA (10 μm plus 100 μm CTZ) for 6 min. The histogram represents the average ± SEM [Ca²⁺]_mit peak maxima for Bax^+/+ and Bax-null oligodendrocytes (n = 35 and 26, respectively; *p < 0.05).