The Release of Sympathetic Amines by Tyramine from the Aortic Walls of Cats

Horns of rat uteri in chambers, perfused with the femoral arterial blood of cats, relaxed during pressor responses to intravenous injections of tyramine, but failed to do so when half this weight of tyramine was put directly into the arterial blood bathing the uterine horn. Concentrations of tyramine, evoking only threshold inhibitions of rat uteri, have been shown to release one or more compounds from the isolated perfused aortae of cats. The substances released inhibit the spontaneous and induced contractions of rats' uteri. Finally both adrenaline and noradrenaline have been demonstrated in extracts of cats' aortae.