1. Sodium desoxycholate in a dose of 2.5×10^-4 gm/ml decreased the slope of phase 4 of the action potential of the sinoatrial nodal cells of the rabbit heart and also decreased the amplitude, duration and rate of rise of the action potential.
2. Its effect on the action potential of the sinoatrial nodal cells is not affected by atropine, but antagonized by norepinephrine.
3. It decreased the conduction velocity of the impulses from S-A node to atrial muscle fibers or to the His' bundle.
4. The sinoatrial cells are more sensitively depressed by sodium desoxycholate than the atrial muscle fibers.