CHEMICAL EXCITATION OF NERVE* 



By Frank Brink, jR.,t Detlev W. Bronk, and Martin G. Larrabee 



Eldridge Reeves Johnson Research Foundation, University of Pennsylvania, 



Philadelphia, Pennsylvania 



One of the noteworthy characteristics of neurones is their sensitivity 

 to changes in the chemical environment. Even within the relatively 

 protected interior of the body, the properties of nerves are subject to 

 modification by variations in the composition of the body fluids. In- 

 deed, the alterations of irritability and the trains of nerve impulses, 

 which are the result of changes in the chemical environment, are among 

 the most important factors involved in the regulation of the activity 

 of the organism. This is one of the significant reasons for studying 

 the chemical activation of nerve. A second reason derives from the 

 current interest in the role of chemical agents in the mechanism of syn- 

 aptic transmission. Furthermore, the investigation of the effects of 

 various chemical agents is one of the most fruitful sources of informa- 

 tion regarding the role of the several chemical components of the nerve 

 structure and of the chemical processes involved in nervous action. 



This last consideration suggests that the most significant chemical 

 agents for use in the study of the processes of activation are those 

 which have an important part in the normal structure of nerve. Cal- 

 cium is such an element. Potassium is another; it modifies the action 

 of calcium, to which it is closely related in the regulation of nerve ac- 

 tion, and it has a marked influence on the electric potential difference 

 across the interfaces at which the nerve comes in contact with its en- 

 vironment. Finally, the effects of acetylcholine on the initiation and 

 conduction of the nerve impulse make an important and timely 

 subject for investigation in such a study as this. It is with the effects 

 of these agents that we shall be primarily concerned. There are 

 others of significance for a general study of this problem, but from 

 these three we can derive many of the basic phenomena involved in 

 chemical excitation. 



The changes in the functional characteristics of a nerve caused by 

 an alteration of its chemical environment are due to the consequent 



* The experimental work reported here has been generously supported by grants from the Supreme 

 Council, Scottish Rite Masons, and from the American Philosophical Society, 

 t Fellow of the Lalor Foundation. 



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