RESERPINE-INDUCED SUPER-SENSITIVITY TO CHRONOTROPIC AND INOTROPIC EFFECTS OF CALCIUM IN RABBIT ATRIA

Abstract

Supersensitivity to the chronotropic and inotropic effects of Ca was demonstrated in spontaneously beating paired atria from reserpine-pretreated (0.1 mg/kg per day, 7 days) rabbits. Supersensitivity to the inotropic effects of Ca in electrically driven left atria was also demonstrated. Atria were driven at 80, 100 and 120 beats/min. At each frequency the reserpine-pretreated atria were more sensitive than controls. Atria were tested under diastolic tensions of 1, 2 and 4 g. As the tension was increased the sensitivity to Ca increased. The sensitivity of reserpine-pretreated atria was greater at each tension that that of control atria. Atria tested at 37.degree. C were less sensitive than those tested at 30.degree. C; the reserpine-pretreated atria were more sensitive than control atria at both temperatures. Reserpine-induced supersensitivity to the inotropic effects of Ca can be obtained and the ability to demonstrate this phenomenon does not appear to be altered by the frequency, diastolic tension or temperature at which each experiment is performed.