SR Ca²⁺ store content is not significantly affected by overexpression of Rem. SR Ca²⁺ store content as assessed by changes in Fluo-3 AM fluorescence (ΔF/F) in response to the application of 1 mM 4-CmC to fibers expressing either YFP (A) or V-Rem (B). Insets show images of loaded fibers before 4-CmC application (left) and at the peak of fluorescence (right). Bars, 100 µm. (C) A comparison of the average peak ΔF/F values for YFP- and V-Rem–expressing fibers is shown. Error bars represent ±SEM.