On the mechanism of sensibilization to catechol-amines by hexonium (Hexamethonium)

The mechanism of the potentiation of catecholamines by hexonium was investigated. In anaesthetized cats hexonium enhanced the presser action of noradrenaline and adrenaline. This effect did not occur when the central nervous system was fully destroyed. After preganglionic sympathectomy of the cervical trunk or extirpation of the superior cervical ganglion, hexonium also failed to increase the response of the nictitating membrane to the electrical stimulation of postganglionic fibres and to adrenaline injected into the femoral vein or external carotid artery. In experiments on isolated spleen of the cat, hexonium did not increase the contraction caused by adrenaline. It is concluded that potentiation of sympathomimetic amines cannot be ascribed to the direct sensitizing action of hexonium on the adrenoreceptors of effector cells.