Effect of caffeine on cardiac contractile activity and radiocalcium movement

¹ Baker Medical Research Institute, Melbourne, Australia

Caffeine induced a positive inotropic response in toad ventricular muscle. The magnitude of the inotropic response was influenced by the concentration of Na⁺ and Ca⁺⁺ in the perfusate and by the rate of stimulation. Caffeine abolished poststimulation potentiation and the "staircase" phenomenon, and evoked an increase in the inward and outward movement of Ca⁴⁵. The positive inotropic activity of caffeine can be related to the changed movement of Ca⁺⁺.