CONCENTRATION OF POTASSIUM IN SERUM AND RESPONSE TO VAGAL STIMULATION IN THE DOG

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Abstract
Seventeen dogs under nembutal anesthesia were employed. Changes in heart rate and in A-V conduction time were recqrded with the Ecg after a variety of physiological procedures at various levels of serum K. These included, 1, stimulation of the distal end of the ligated right vagus; 2, pressure on the larynx and carotid sinus; 3, elicitation of the carotid sinus reflex by the transient hypertension of adrenalin inj.; and 4, the intraven. inj. of 0.05-0.10 mg. of acetyl-[beta]-methyl-choline chloride. The influence of acetyl-[beta]-methylcholine chloride was also investigated by means of a balloon and tambour system. The level of serum K was increased by the slow intravenous infusion of isotonic KCl or by the autointoxication with K consequent to bilateral ureteral ligation. In some expts. the level of Ca in the serum was also increased by inj. In all expts. there was a marked increase in effectiveness of parasympathetic stimulation or acetyl-[beta]-methylcholine chloride inj. at increased levels of serum K, and this increase was noticeable at levels at which no effects of the K on heart rate or intracardiac conduction were to be seen. The effect was completely reversible and was not antagonized by increasing the Ca content of the serum. Variation in the level of serum K did not alter the hypertensive response to adrenalin.