Figure 5.

Depolarization-evoked calcium signals in GLT and GLT-α₁ subunit–transfected cell lines. (A) Series of fluo-3 fluorescence images during the depolarization with a high potassium solution (47 mM) at the times indicated in nontransfected GLT dysgenic cells. These cells showed no fast or slow calcium signals (Bar = 10 μm). (B) Series of fluo-3 fluorescence images during a depolarization with a high potassium solution at the times indicated in GLT dysgenic cell lines transfected with the plasmid containing the α₁ subunit of the DHPR. In contrast to what we observed in GLT myotubes and in the mock-transfected cells (GLT-NEO), we observed a slow depolarization-evoked calcium signal. Note that the slow transient (documented in D) lasts even longer than the one from primary cultures shown in Figs. 1 C and 2 A). Bar = 20 μm. (C) Relative fluorescence variation in an ROI during potassium depolarization at the time indicated in GLT cells. (D) Relative florescence in an ROI in GLT cells transfected with the α₁ subunit. (E) Relative fluorescence variation in an ROI during potassium depolarization at the times indicated in control NLT cells.