Figure 3. Inhibition of IP₃ signalling inhibits PE-induced stimulation of I_Ca,L.

A, original records showing the effects of PE to stimulate I_Ca,L recorded with a ruptured patch method. PE elicited a typical increase in I_Ca,L amplitude. B, another atrial myocyte in which I_Ca,L was recorded during intracellular dialysis of heparin (1 mg ml⁻¹) contained within the pipette solution. PE failed to increase I_Ca,L amplitude. In two additional series of experiments, PE was tested in the absence and presence of 2 μm 2-APB or 10 μm xestospongin C (incubation 2 h) using a perforated patch recording method. C, summary of the inhibitory effects of heparin, 2 μm 2-APB or 10 μm xestospongin C. Each IP₃ receptor blocking agent significantly inhibited PE-induced stimulation of I_Ca,L. Numbers in parentheses indicate the number of cells tested in each experiment. *P < 0.05.