Abstract
The action potentials of the atrial, ventricular and sinoatrial pacemaker cells of the golden carp were recorded by means of a microelectrode technique. Acetylcholine (10-6g/ml) decreased the slope of the diastolic depolarization of the pacemaker cells. It shortened the action potential duration and caused the hyperpolarization of the atrial fibers. Ventricular fibers are insensitive to acetylcholine. Adrenaline (10-6g/ml) increased the slope of the diastolic depolarization of the pacemaker cells. It increased the amplitude of the plateau phase of both the atrial and ventricular fibers and prolonged their action potential duration. In the atrial fibers the acetylcholine effect was blocked by atropine, while the adrenaline effect was blocked by propranolol, but not by phenoxybenzamine. The pacemaker cells were more resistant to tetrodotoxin than the atrial fibers, while the reverse was true for manganese ions. These results indicate that the action potentials of the myocardial cells of the golden carp are similar to those of mammals or amphibians.
