Fig. 5. Effect of ISO on Ca²⁺ transient and whole membrane current during long depolarizations. (A) The top panel shows the stimulation protocol; the resulting Ca²⁺ transients are shown below in the absence (black line) or the presence (gray line) of 1 µmol l^–1 isoproterenol (ISO). (B) Simultaneous recordings of whole membrane current. The time scales corresponds to 5 s (left) and 4 s (right). (C) Simultaneous recordings of Ca²⁺ transients and membrane currents during a rapid caffeine application in control, with 1 µmol l^–1 ISO and after washout of ISO. Notice that the effects of ISO on both Ca²⁺ transient and membrane current were fully reversible.