Figure 4. Ca²⁺ transients evoked by depolarization to 0 mV.

(A) Typical examples of simultaneous recording of I _Ca and Ca²⁺ transient (image and ΔF/F₀) in ventricular myocytes from rats (left) and ground squirrels (right). The fractional shortening (FS) was determined by edge-detection of Ca²⁺ transients. (B) The amplitude of Ca²⁺ transient (ΔF/F₀) and (C) the fractional shortening (FS) reflecting the amplitude of contraction were compared between rats (n = 12 cells from 8 animals) and ground squirrels (n = 16 cells from 8 animals). (D) The gain of E-C coupling was calculated as the ratio between ΔF/F₀ and I _Ca density. (E) The full-duration at half-maximal (FDHM) and (F) the time constant (τ) of second half decay of Ca²⁺ transient were compared between rats (n = 12 cells from 8 animals) and ground squirrels (n = 16 cells from 8 animals).