Effect of Catecholamine Depletion on an Index of Myocardial Contractility in Isolated Rabbit Hearts.

Abstract

Summary Isolated hearts from 11 untreated rabbits, 9 pretreated with 10 mg/kg guanethidine, 12 pretreated with 20 mg/kg guanethidine and 6 pretreated with 3 mg/kg reserpine were subjected to graded, moderate stretch by means of a clip attached to the apex of the left ventricle. Active tension de-deloped by the ventricles as a function of stretch was measured. The low dose of guanethidine depressed tension development but reserpine and the higher dose of guanethidine did not interfere conspicuously with tension development. The drugs produced 70 to 94% reduction in catecholamine content of the left ventricle. It is concluded that drastic reduction in catecholamine content of the left ventricle of the rabbit does not necessarily result in severe impairment of its contractility.