Inhibition by Phenoxybenzamine of the Noradrenaline Releasing Effect of Tyramine

Hedqvist, P., A. Oliverio and L. Stjärne, Inhibition by phenoxybenzamine of the noradrenaline releasing effect of tyramine. Acta physiol. scand. 1968. 72. 385–391. After loading the isolated, perfused dog spleen with tritium-labeled noradrenaline intra-arterial injections of tyramine were found to cause an increase in the overflow of both labeled, exogenous, and of endogenous noradrenaline into the effluent from the organ. The overflow response to 2–3 consecutive injections of a standard dose of tyramine remained relatively constant. Increasing the tyramine dose up to 100-fold resulted in a marked increase in the pressor response but did not produce a proportional increase in the overflow of noradrenaline. Phenoxybenzamine added to the perfusion fluid strongly reduced or completely abolished the overflow response to tyramine.