Acetylcholine (ACH), a neurotransmitter secreted by postganglionic
parasympathetic termini, plays a key role in the regulation of
spontaneous activity and excitation propagation in sinus node (SN) of
mammals in normalcy and pathology. In this work, we used computer
simulation to study the effect of ACH on currents of single cells of
true and latent pacemakers of rabbit sinus node. It is shown that ACH
differentially affects the spontaneous activity of pacemaker cells,
depending on the maximal rate of action potential rise (dV/dtmax).  At
dV/dtmax < 1.15 V/s, spontaneous activity was stopped without
deceleration of initial rhythm; at greater dV/dtmax values,
spontaneous activity was stopped against the background of
deceleration of initial rhythm, which is related to different ratio of
calcium currents ICa,L and ICa,T.