| Abstract: | Some critical remarks on the interpretation of staircase and potentiation phenomena (rabbit heart muscle). Isometric contractions of rabbit papillary muscles and atrial strips were investigated at temperatures from 13.2 degrees C to 35 degrees C after rests of different duration at constant stimulation frequency before rest, in a period after rest and in a transition phase following a step of stimulation frequency. Changes in potentiation as well as changes in dynamics after rest and dynamics after steps of stimulation frequency are caused by lowering the temperature. Any hypothesis on the subject of Ca-movements between intracellular stores would have to account for changes in potentiation, staircase phenomena and the development of after-contractions at low temperatures. |
