202 CORTEX 



Insulin and epinephrine are antagonists. The mobilization 

 of sugar induced by epinephrine is counteracted by the stimula- 

 tion of sugar utilization and the inhibition of glycogenolysis in 

 the liver which insulin induces. However, this antagonism 

 between epinephrine and insulin is limited to their effects on 

 carbohydrate metabolism. Epinephrine is capable of causing 

 glycogenolysis after insulin poisoning and hence may be used 

 as an antidote to overdosage of insulin, when the liver store 

 of glycogen is not depleted. That hyperglycemia, induced by 

 insulin injections and probably also by other methods, causes 

 an increased epinephrine secretion, is shown by the depletion 

 of the epinephrine stores of the adrenals after insulin poisoning 

 and by the reaction of the denervated heart and iris of the cat. 

 These reactions are absent in adrenalectomized animals and 

 may be prevented by injections of glucose. 



The injection of large doses of insulin causes a depletion of 

 the liver glycogen and a considerable diminution of the muscle 

 glycogen. After removal of the adrenals, however, there is 

 little effect on the muscle glycogen. 151 Since epinephrine 

 also depletes the liver of its glycogen and diminishes the glyco- 

 gen content of the muscles, the latter effect when following in- 

 sulin injections has been attributed to epinephrine. 



In hypophysectomized rabbits, insulin hypoglycemia still 

 liberates epinephrine into the blood stream, but this epineph- 

 rine fails to restore the blood sugar to the normal level in 

 spite of the presence of ample reserves of liver glycogen. There 

 is also a diminution in the hyperglycemic response to injected 

 epinephrine. 124 



The question of whether or not emotional hyperglycemia is 

 due to increased epinephrine secretion should be settled by 

 noting the blood sugar changes occurring in adrenalectomized 

 animals, maintained on adequate quantities of cortical hor- 

 mone following emotional disturbances. 



