RETENTION OF EXOGENOUS NOREPINEPHRINE AND RECOVERY OF THE RESPONSES TO TYRAMINE AND 1, 1-DIMETHYL-4- PHENYLPIPERAZINIUM IODIDE AFTER RESERPINE

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

It is generally acceptedthat reserpine interferes with the binding and storage of norepinephrine. Administration of H³ -norepinephrine at various intervals after reserpine showed that the rat heartrecovered its ability to accumulate norepinephrine at 72 hr. Only when this much time had elapsed did the administration of 20 mg/kg of tyramine cause the same percentage of depletion of catecholamines as in normal animals. A study of the effects of reserpine on subcellular distribution of norepinephrine showed that at 5 min there was a shift of norepinephrine from the particulate to the soluble fraction. However, at 72 hr the pattern of subcellular distribution of norepinephrine returned to normal. Also at 72 hr, the response of isolated atria (from animals pretreated with reserpine) to tyramine and DMPP returned to almost normal. The sensitivity of these atria to norepinephrine was not altered. Thus these results show a striking correlation between the time course of the recovery of the ability to accumulate H³-norepinephrine and the time course of the recovery of theresponses to tyramine and 1, 1-dimethyl-4-phenylpiperazinium iodide.