Fig. 7.

Diastolic Ca²⁺_i transient parameters correlate with pacemaker frequency. a Typical Ca²⁺_i transients of a non-stimulated SAN cell with inhibited I _f (2 mM cesium) and I _K,ACh (100 nM tertiapin) that was successively exposed to normal Tyrode’s solution (black trace), 12.5 nM ACh (red trace), 50 nM ACh (blue trace), 100 nM ACh (green trace) and 1,000 nM ACh (purple trace). b Average frequency–ACh relationship of non-stimulated SAN cells (n = 14) with inhibited I _f and I _K,ACh. c Correlation between fold change in interbeat interval (IBI) and fold change in time constant of Ca²⁺_i transient decay. Solid line is the linear best fit to the data (r ² = 0.98). d Correlation between fold change in IBI and fold change in the slow diastolic Ca²⁺_i rise. Solid line is the linear best fit to the data (r ² = 0.73)