GABA-induced [Ca²⁺]_i elevation in cultured NG2 cells. (A) Confocal images of cultured NG2 cells loaded with Fluo-4 AM before (control) and during perfusion with 1 mM GABA. Bar, 20 µm. (B) Averaged time course of 1 mM GABA–induced [Ca²⁺]_i elevation in cultured NG2 cells and its blockage by 10 µM bicuculline. (C) Summary of [Ca²⁺]_i changes in NG2 cells perfused with normal solution (ECS) or solution containing 1 mM GABA with or without (control) various treatments. Data are averaged during 30–80 s after the onset of perfusion with GABA, normalized by the mean fluorescence intensity obtained during the control period (0–50 s before GABA perfusion) for each cell. TTX wash and KB-R wash, recovery of the GABA-induced [Ca²⁺]_i elevation after 10 min and 5 min wash out of 1 µM TTX and 10 µM KB-R7943, respectively. **, P < 0.01 compared with ECS group. (D, left) Confocal images of cultured NG2 cells cotransfected with pGFP + scrambled siRNA (siRNA-Control), pGFP + siRNA-Nav1.x, or pGFP+siRNA-NCX1, respectively. (D, middle and right) [Ca²⁺]_i images of untransfected (arrowheads) and transfected (arrows) NG2 cells loaded with the Ca²⁺ dye Rhod2 AM before and during perfusion with 1 mM GABA, respectively. Images in each row were sampled from the same field. Note that GABA induced apparent [Ca²⁺]_i elevation in untransfected cells or cells transfected with siRNA-control, but not in cells transfected with either siRNA-Nav1.x or siRNA-NCX1. Bars, 20 µm. (E) Summary of GABA-induced [Ca²⁺]_i changes in NG2 cells with or without various transfections. Data are averaged during 30–100 s after the onset of perfusion with GABA, subtracted by the mean fluorescence intensity obtained during the control period (0–50 s before GABA perfusion) for each cell. **, P < 0.01 compared with siRNA control group. Error bars represent mean ± SEM.