Pressor Effects of Adrenaline, Noradrenaline and Reflex Vasoconstriction Sensitised by Low Concentrations of Ganglion Blocking Drugs

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Abstract
In cats, rats and pigeons, concentrations of hexamethonium, tetra-ethylammonium and pentolinium ions too low to influence transmission in autonomic ganglia potentiate the pressor effects of adrenaline, noradrenaline and of reflex vasoconstriction. These effects of the ganglion blocking drugs are not modified by spinalization or by acute adrenalectomy but are absent after pretreatment of an animal with reserpine or of a tissue by postganglionic sympathetic denervation. These concentrations of ganglion blocking drug increase the uptake of noradrenaline by the adrenal medulla, increase the total amine and the proportion of it present as adrenaline in this gland, fail to antagonise adrenal medullary depletion of catecholamine by reserpine and can reverse a pre-existing potentiation of the pressor effects of adrenaline and noradrenaline induced by cocaine.