The action of sympathomimetic amines on the rate of the denervated heart of the cat

In a previous paper it was shown that the action of noradrenaline, but not that of adrenaline, on the rate of the acutely denervated heart of the cat was potentiated by cocaine or chronic sympathetic denervation (Innes & Kosterlitz, 1951). At that time, no theoretical explanation was offered for the observed facts as it was felt that the analysis was still incomplete. Burn & Robinson (1952) have put forward the view that the potentiating action of cocaine and chronic denervation on the responses of the nictitating membrane to noradrenaline may be caused by inhibition or loss of the enzyme amine oxidase. For this reason it seemed of interest to study the chronotropic action of adrenaline and noradrenaline in the presence of substances inhibiting amine oxidase. In view of the fact that cobefrine or corbasil, the propanol homologue of noradrenaline, is not oxidized by amine oxidase (Blaschko, Richter & Schlossmann, 1937) this substance was included in the present investigation.