Effect of Adrenergic Blocking Agents on Tyramine-Induced Release of Catecholamines from the Cat Heart.

The release of catecholamines produced by tyramine in the isolated cat heart is inhibited by phenoxybenzamine and GD-131 but not by phentolamine or dihydroergotamine. Inhibition of the release of catecholamines is associated with a marked reduction in the positive inotropic effect of tyramine. The possibility is suggested that β-haloalkylamines may interfere with the release of catecholamines in vivo as well as inhibiting the effects of catecholamines on effector cells.