NERVE ACTIVITY 



virtually nothing was known about chemical reactions associated 

 with nerve activity, as was stated by Feng in his review on heat 

 production in nerve (9) ; this was in striking contrast to all the 

 great advances in this field obtained with physical methods, 

 especially electrical recordings. During the decade between the 

 appearance of the Perspectives and the first volume of the Currents 

 in Biochemical Research essential progress had been achieved (17). 

 Investigations were carried out following lines of approach 

 similar to those which had been applied to the biochemistry of 

 muscle. 



SEQUENCE OF ENERGY TRANSFORMATIONS 



These studies had revealed that the action of acetylcholine 

 is associated with the elementary process of conduction, i.e., 

 acetylcholine is necessary for generating the bioelectric potentials 

 which propagate the impulse in conducting tissues. The se- 

 quence of energy transformations was established, the enzyme 

 systems associated with the formation and hydrolysis of acetyl- 

 choline were studied, and acetylcholine was integrated into the 

 metabolic pathways of the nerve cell. A variety of chemical and 

 electrical processes were correlated. The use of electric tissue, 

 since 1937, was helpful in overcoming many difficulties. Electric 

 organs are the most powerful bioelectric generators known in 

 nature and the choice of this material proved decisive in many 

 respects, especially, however, in determining the sequence of 

 energy transformations. These organs contain acetylcholinester- 

 ase in amazingly high concentrations: 100 g. of organ (fresh 

 weight) may hydrolyze 200 to 400 g. of acetylcholine per hour, 

 although the tissue is poor in protein (2 per cent) and its water 

 content is very high (92 per cent). Since the electric organs are 

 highly specilized as to their function, the remarkable concentra- 

 tion of acetylcholinesterase appeared suggestive as to a direct 

 relationship with the process by which bioelectric currents are 

 generated. A direct proportionality exists indeed between 

 voltage per centimeter and acetylcholinesterase concentration. 



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