Influence of ouabain on the spontaneous oscillations frequency in cardiac pacemaker

The behaviour of true-pacemaker cells of rabbit-heart has been analyzed in presence of various concentrations of ouabain, to verify the influence of active transport on the spontaneous oscillations. Curves of frequency f via temperature T of bathing solution have been deduced. The results obtained show that ouabain in the concentration range 10-7-5*10-5 mM/l influences both the parameters of regression lines f (T): precisely there is an increase in slope and absolute frequency values in the temperature range 28-38 °C. We have also observed that a temperature increase causes an increase of maximum diastolic potential (MDP), however the overshoot values remain unmodified. These results agree with the hypothesis that a metabolic activity, as active transport across membrane, influences the mechanism of pacemaker spiking generation.