Cholinergic control of heart rate by nitric oxide is site specific.
Herring N., Danson EJF., Paterson DJ.
Parasympathetic control of heart rate involves the exocytotic release of acetylcholine and muscarinic receptor regulation of pacemaking currents. Endogenous nitric oxide can potentially regulate all of these processes; however, recent work suggests that the main functional role of nitric oxide lies in the modulation of acetylcholine release.