Lack of Influence of the Sympathetic Nervous System on the Calorigenic Response to Thyroxine

¹ From the Department of Physiology, Washington University School of Medicine and the Jewish Hospital, Saint Louis, Missouri

Normal rats as well as thyroparathyroidectomized rats concurrently given thyroxine and an adrenergic blocking dose of Dibenzyline show the expected rise in rate of oxygen consumption. After bilateral adrenal demedullation the resting rate of oxygen consumption is not significantly different from normal, and injection of a large dose of thyroxine either with or without concurrent administration of adrenergic blocking doses of Dibenzyline is followed by a significant rise in the rate of oxygen consumption. Our data and other pertinent published data lend support neither to the claim that the calorigenic effect of exogenous thyroxine is dependent upon the presence of normally acting adrenal medullary hormones nor to the claim that the metabolic changes of thyrotoxicosis are due to the physiological effects of epinephrine and norepinephrine as augmented by the thyroid hormones.