Abstract

After the intravenous administration of H³-norepinephrine, it was taken up by the heart and slowly released over a period of days. Long-acting monoamine oxidase inhibitors blocked the slow release of H³-norepinephrine. Long-acting and short-acting monoamine oxidase inhibitors blocked the releasing action of reserpine on H³-norepinephrine in the heart. On the basis of these observations it is proposed that monoamine oxidase inhibitors elevated the catecholamine concentration in certain tissues by blocking the release of the hormone from its binding site.