Slowed rate of electrically evoked Ca²⁺ transients in mag-fluo-4–loaded FDB fibers from IT/+ mice. (A) Representative single electrically evoked Ca²⁺ transients elicited during a brief 0.1-Hz train of stimulation in FDB fibers from WT (left) and IT/+ (right) mice. Sampling rate was 10 kHz. (B) The first derivative of the mag-fluo-4 traces within the region marked by two arrows for the traces shown in A. (C) Box plot representation for the dataset of peak electrically evoked mag-fluo-4 transients (ΔF/F_max) in FDB fibers from WT (left) and IT/+ (right) mice. (D) Box plot representation for the dataset for the peak of the first derivative of electrically evoked mag-fluo-4 transients (d(ΔF/F)/dt) in FDB fibers from WT (left) and IT/+ (right) mice. (E) Average (±SEM) peak electrically evoked Ca²⁺ transients (ΔF/F_max) across FDB fibers from WT (n = 3; black bar) and IT/+ (n = 3; gray bar) mice (12–29 fibers/mouse). (F) Mean (±SEM) peak of the first derivative (d(ΔF/F)/dt) across FDB fibers from WT (n = 3; black bar) and IT/+ (n = 3; gray bar) mice (12–29 fibers/mouse).