Fig. 3

Control of basal I _Ca,L by β-AR-PKA signaling cascade in RVMs. a ACh alone had no effect on the basal I _Ca,L and dose-dependently but incompletely inhibited ISO-stimulated I _Ca,L. b After stimulation of I _Ca,L with ISO (1 µM), the intracellular solution was changed to one containing 20 µM PKI(15-22), and the current returned to basal level. The dotted line indicates spontaneous run-down. c Bar graphs representing the average effect of ACh alone and ISO, alone or in the presence of either ACh or PKI(15-22), on I _Ca,L. IBMX (100 µM) (d) and Cal A (100 nM) (e) near maximally stimulate basal I _Ca,L. When the myocyte was superfused with Cal A and when the current was at its maximal stimulation, ISO (1 µM) induced only a small additional stimulation of I _Ca,L. The current traces shown in d were recorded at the times indicated by the corresponding letters on the main graphs. f Bar graphs representing the average effect of IBMX alone and Cal A, alone or in presence of ISO, on I _Ca,L. *p < 0.05, **p < 0.01, compared with basal I _Ca,L or between indicated groups