Prolonged constriction of the bloodvessels by subcutaneous injection of adrenalin into the ear of a rabbit. A demonstration

Abstract

Intravenous injection of adrenin causes a rise of blood pressure which is due to a constriction of the bloodvessels. The rise lasts only several minutes. The shortness of the duration of this rise is explained by the escape of the injected adrenin from the circulation into the surrounding tissues where it becomes destroyed by the alkalinity of the tissue fluid. Subcutaneous injection of adrenin produces only a slight effect upon the blood pressure. As is well known the bloodvessels of the rabbit's ears are easily visible. We have observed that a subcutaneous injection of adrenin into the lower part of one of the rabbit's ears causes a striking and long lasting constriction of the bloodvessels of the corresponding ear. It is this phenomenon which we wish to demonstrate. If the injection is given in the proximity of the central artery, the constriction of the bloodvessels of the entire ear sets in two or three minutes after the injection. If it is given at some distance from the central artery, the pallor develops slowly. In either case the vessels remain more or less strikingly constricted for many hours, sometimes even seven hours. Injection of a different solution, saline, for instance, does not exert such an effect. It is evident that in the case of the ear the adrenin is not destroyed rapidly by the tissues surrounding the bloodvessels.