Effects of the Electrical Stimulation of the Central Gray Stratum of the Midbrain on the Blood and Myocardial Catecholamine

Abstract

Effects of the electrical stimulation of the central gray stratum of the midbrain on the blood and myocardial catecholamine were studied in 26 normal dogs anesthetized with intravenous injection of α-chloralose.
(1) Blood pressure showed a biphasic pressor response consisting of a sharp rise with tachycardia during stimulation and a relatively slow elevation with bradycardia after stimulation.
(2) The concentration of both arterial and adrenal venous catecholamine was determined simultaneously by the fluorimetric method. Adrenal venous catecholamines secretion increased most strikingly during stimulation. In the animal with the intact lumboadrenal veins both peripheral arterial norepinephrine and epinephrine levels elevated also immediately after stimulation. The arterial norepinephrine concentration when adrenal venous flow was separated from systemic circulation increased during stimulation, and the epinephrine level of the artery elevated immediately after stimulation.
(3) The release of norepinephrine from the heart was confirmed by measuring the plasma norepinephrine level in bloods obtained simultaneously from the coronary sinus and femoral artery using coronary sinus catheterization under fluoroscopy.
(4) The myocardial norepinephrine content increased significantly by stimulation, but the epinephrine level remained almost unchanged.
A few possible explanation for these data was discussed.