EFFECT OF VARIOUS PROCEDURES ON THE REPLETION OF CARDIAC CATECHOLAMINE STORES AFTER TYRAMINE

¹ Department of Pharmacology, College of Medicine, Howard University, Washington, D.C.

The effect of tyramine on the release of endogenous catecholamines and H3-norepinephrine in the rat heart showed that tyramine initially released labeled and unlabeled norepinephrine to about the same extent. After 4 hours, the specific activity of the norepinephrine was significantly elevated in the animals treated with tyramine. Maximum depletion of endogenous norepinephrine occurred at 4 hours, and complete repletion was seen at about 16 hours. Adrenal demedullation or treatment of animals with monoamine oxidase inhibitors failed to affect the repletion of cardiac catecholamines. Treatment of animals with imipramine or with inhibitors of dopamine -oxidase, such as tetraethylthiuram disulfide (Antabuse or disulfiram) or 4-bromo-benzyloxyamine (NSD-1055) retarded the repletion of cardiac catecholamines in tyramine-depleted animals. While bretylium or cocaine, given before tyramine, failed to affect release or rate of restoration, given after tyramine, it significantly retarded the repletion of cardiac catecholamine.