Figure 3. Effects of agonists upon the time-dependent decay of I_Ca,L.

A, I_Ca,L was evoked by voltage steps to +10 mV in cells bathed in extracellular solution containing 2 mm Ca²⁺. These normalised records were obtained from four representative cells. Each record consists of two superimposed traces which were recorded first under the indicated experimental condition and then following the addition of 10 μm carbachol. The dotted lines indicate the zero level. The time scale to the left applies to all four sets of traces. B, the biphasic decay of I_Ca,L evoked by a voltage step to +10 mV was analysed and the amplitudes of the fast and slow components of the double-exponential function (Origin 4.1) were extracted. Here, the amplitude of the fast component of decay is expressed as a proportion of the total current amplitude (A_f/A_f + A_s). Cell currents were recorded first either under basal conditions (n = 8) or in the presence of 2 (n = 9), 20 (n = 6) or 100 nm (n = 5) isoproterenol (□) and then following the addition of 10 μm carbachol (▪).