The negative chronotropic effect of adenine derivatives and acetylcholine on frog and rat hearts

The negative chronotropic effect of ATP on frog as well as rat hearts was not influenced by atropine while the same atropine concentration completely abolished the negative chronotropic effect of Acetylcholine. From these results the conclusion was drawn that the negative chronotropic effect of ATP cannot be ascribed to an acetylcholine release from the efferent vagus fibers. In contrast to Beznak's results we also did not find an acetylcholine releasing activity of ATP on the motor nerve endings in the frog's abdominal muscle.