EFFECT OF PROLONGED BETA-RECEPTOR BLOCKADE ON DRY WEIGHT AND ELECTROPHYSIOLOGICAL RESPONSES OF RABBIT HEARTS

Abstract Three groups of rabbits were injected twice daily subcutaneously with saline solution, propranolol, or practolol for 6 weeks. Their hearts were then removed and weighed wet and dry, and the atria were used for measurement of intracellular potentials, contractions, response to isoprenaline, and other functional indices. The ventricular dry weights of the propranolol-treated group were 18·6% less than the controls, and the practolol group 31·2% less. The intracellularly recorded action potentials of the practolol group were prolonged. There was no evidence of any negative inotropic effect or altered sensitivity to isoprenaline in either treated group.