Effect of antisympathomimetic drugs on the plasma concentrations of catechol amines.

Intravenous injection of phenoxybenzamine, choline 2,6-xylyl ether bromide (xylocholine, TM 10), piperoxane or dihydroergotamine increases the vasopressor activity of blood plasma, collected from cats under chloralose anaesthesia. The increased vasopressor activity that follows the administration of piperoxane is due to an increase of adrenaline and noradrenaline in the plasma. Cross-circulation experiments show that catechol amines are liberated from the spleen by piperoxane.