Figure 1. Inhibition of Ado- and AP₆A-induced bradycardia by CPX in a perfused heart.

R-R intervals from surface ECG, averaged over three cycles, have been plotted against time; t = 0 corresponds to the end of the equilibration time (30 min after mounting the heart in the Langendorff apparatus). Boli of 300 μl of solutions containing ACh, AP₆A and Ado (each at 100 μm) were injected at the times indicated. A, control; B, in the presence of CPX (20 μm) in the perfusing fluid; C, recovery after washout of CPX.