Abstract

Reduction in the sodium concentration in the medium from 156 mM to 91 mM stimulated the force of contraction of isolated rabbit atria without significantly altering the spontaneous rate. Low sodium potentiated the chronotropic and antagonized the inotropic effect of acetylcholine. It was also demonstrated that the rate of onset of the chronotropic effect of acetyleholine was increased by low sodium, whereas the rate of onset of the inotropic effect was decreased.