98 MEDULLA 



hances the epinephrine discharge caused by splanchnic stimu- 

 lation, which is what one would expect if the discharge of 

 epinephrine caused by splanchnic stimulation were due to the 

 liberation of acetylcholine. The action of acetylcholine or of 

 splanchnic stimulation of the adrenal medulla manifests the 

 two types of peripheral effects which the choline esters show 

 generally; viz., 1) a "nicotine" action which is abolished by 

 large doses of nicotine and 2) a "muscarine" component 

 abolished by small doses of atropine. Feldberg and his collab- 

 orators conclude that acetylcholine is the humoral transmitter 

 of splanchnic impulses to the adrenal medulla. This cho- 

 linergic action of the preganglionic sympathetic fibers is not 

 limited to the splanchnic nerves. 



FACTORS AFFECTING EPINEPHRINE SECRETION 



Sensory stimulation. After stimulation of sensory nerves, 

 such as the central end of the sciatic, brachial, or vagus, the 

 blood of the adrenal vein induces the characteristic reactions 

 of epinephrine. It has, therefore, been claimed that such 

 stimuli, by reflex action, cause a discharge of epinephrine. 

 The evidence adduced by earlier workers was criticized by 

 Stewart and Rogoff. 591 As these authors pointed out, ob- 

 servations made without regard to changes in the rate of blood 

 flow through the adrenals and without quantitative determina- 

 tions of the amount of epinephrine liberated per unit of time 

 offer no criterion for determining the influence of stimulation 

 of afferent nerves. 



Stewart and Rogoff's failure to demonstrate that sensory 

 stimulation does not increase the secretion of epinephrine was 

 due probably to the experimental methods which these authors 

 utilized. As shown by Satak6 et alii, 546 with the "cava-pocket" 

 procedure on anesthetized dogs or cats, one does not obtain 

 an increased secretion of epinephrine. However, in the non- 

 anesthetized dog the output of epinephrine is increased from 

 two to five times by stimulation of sensory nerves. Narcosis 



