Effect of Atropine on the Responsiveness of the Adrenal Medulla to Acetylcholine

The experiments were performed in dogs anesthetized with Evipansodium. The adrenal venous blood was collected through the lumbar route and was estimated for adrenaline using the arseno-molybdic acid method of Bloor and Bullen. Intravenous injection of acetylcholine in doses of 2.0mg., 1.5mg. or 1.0mg. per kg. of body weight was made after administrations of atropine in doses of 1mg. and 10mg. per kg., respectively. In some cases it was also made without administering atropine previously. After the administration of atropine in a dose of 10mg. per kg., a definite increase in the adrenaline secretion rate was elicited by the injection of acetylcholine in almost the same magnitude as that caused by acetylcholine after atropine in a dose of 1mg. per kg. or without atropine. From these experimental results, it may be concluded that the adrenaline-secretory action of acetylcholine is not inhibited even by large doses of atropine.