Effects of Chlorpromazine and Propranolol on Left Ventricular Systolic Pressure, ECG, and K+Efflux in the Isolated Perfused Rat Heart

Isolated rat hearts perfused with a perfusate from which K+had been omitted and replaced by Rb+had a spontaneous rate of contraction which was about 5 % slower than that of the hearts perfused with K+‐containing perfusate, while the electrically driven hearts had a contractile force which was about 10 % lower. Isoprenaline and glucagon caused a maximal increase in contractile force of 60 % and 50 % respectively which is equal to the increase obtained with a K+‐containing perfusate. Chlorpromazine (C), d,l‐propranolol (d,l‐P) and d‐propranolol (d‐P) in concentrations from 10‐5M to 5 × 10‐5M caused dose dependent decreases in a) the heart rate from 135 ± 7 beats/min. (mean ± S. D.) (4 controls) to a minimum of 62 (C), 61 (d,l‐P) and 60 (d‐P). b) impulse conduction velocity expressed as PQ‐1 from 12 ± 2.1 sec. (4 controls) to a minimum of 6.6 (C), 4.9 (d,l‐P) and 4.8 (d‐P). c) left ventricular systolic pressure from 95 ± 3 mmHg (4 controls) to a minimum of 56 (C), 45 (d,l‐P) and 44 (d‐P). d) potassium efflux from 4.2 ± 0.2 meq√g dry weight × 10‐2(8 controls) to a minimum of 2.9 (C), 2.7 (d,l‐P) and 2.6 (d‐P). It is suggested that the effects can be explained as secondary to drug induced changes in the cell membrane.