Actions of Bretylium and Guanethidine on the Uptake and Release of [³h]‐noradrenaune

The effect of bretylium and guanethidine has been studied on the uptake and the spontaneous and reserpine-induced release of [(3)H]-noradrenaline in the rat heart and in the splenic nerve endings of the cat. Bretylium and guanethidine inhibited the uptake by the heart of circulating [(3)H]-noradrenaline. Bretylium blocked spontaneous and reserpine-induced release of [(3)H]-noradrenaline, while guanethidine caused release and partially antagonized the reserpine-induced release. Both compounds produced a transient liberation of [(3)H]-noradrenaline from splenic nerves, but blocked the release of the [(3)H]-catechol amine following stimulation of the splenic nerve.