[Potentiation and staircase phenomena in rabbit heart atrium and their connection with inotropic vague effects]

At spontaneously beating rabbit atria in vitro longtime pauses of contraction were produced by vagal stimulation. After finishing the stimulation at once contractions took place; the first of them was potentiated. During the vagal pauses various beat interval programs were realized. After removing the sinusoidal node the same programs were repeated by variation of drive interval length. Their effects were compared to the effects in vagal pauses. All these effects were simulated by a two stores three phases model. This model allows description of potentiation and staircase phenomena as well as inotropic vagal effect and inotropic vagal escape. It suggests a connection between this two kinds of phenomena.