Analysis of the effect of morphine and trimeperidine on the uptake and liberation of noradrenalin by myocardial tissue

The effect of morphine and trimeperidine on the concentration, uptake, and liberation of noradrenalin (NA) in the rat myocardium was investigated. Trimeperidine lowers the NA level in the myocardium. Morphine does not affect the liberation of NA-¹⁴C from the isolated perfused heart, whereas trimeperidine significantly increases it, affecting both the slow and the rapid release of the mediator. Trimeperidine does not affect the uptake of NA-¹⁴C by the perfused heart but morphine significantly lowers it. Competition between morphine and NA is characterized by an incomplete inhibition effect: Morphine and NA mutually affect the affinity of each other for the receptor and their interaction depends on their relative concentrations.Laboratory of Pharmacology of the Cardiovascular System, Institute of Pharmacology, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR V. V. Zakusov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 82, No. 11, pp. 1345–1347, November, 1976.