CHAPTER LXXV 



Neuronal metabolism 1 



,2 



L. G. ABOOD 



Departments of Psychiatry and Biochemistry, University of Illinois 

 College oj Medicine, Chicago, Illinoi I 



CHAPTER CONT E N T S 



Cytochemistry 



Mitochondria 



Myclinization 



Structural Elements, Growth and Differentiation 



Substrates of the Neuron 



Nucleic Acids 



Relationship of Chemistry to Function 



until the last decade any attempt to discuss tin- 

 problem of 'neuronal' metabolism was cither 

 burdened with speculation or completely destined to 

 failure, primarily because the concept of the 'neuron' 

 was not sufficiently delineated from a chemical or 

 biochemical point of view. With the application of 

 highly refined microchemical and microphysical 

 techniques to the chemistry of the single cell, not only 

 has it been possible to obtain information about the 

 chemistry of the adult neuron at rest, but considerable 

 knowledge is accumulating on the biochemical 

 changes during growth and activity, as well as under 

 pharmacological and pathological conditions. Al- 

 though the neuron comprises the main functional 

 unit of the nervous system, morphologically it is 

 embedded in a syncytium of neuroglial elements, 

 the biochemical and even functional role of which 



1 The unpublished work was supported by a contract from 

 the Office of Naval Research 



2 The purpose of this chapter is not to present a compre- 

 hensive review of the biochemistry of the nervous system, but 

 rather to indicate general trends and, wherever possible, to 

 relate neurochemistry to neural function. For more extensive 

 biochemical details, the reader is referred elsewhere (27, 63, 

 95, 1 18). 



remains obscure. To what extent the chemistry and 

 function of the neuron is related to the neuroglial 

 components is a problem in itself, but the necessitv 

 for studying each cell type individually remains acute. 



Even in the case of 'peripheral nerve,' the contri- 

 bution of connective tissue and endoneurial elements 

 to the overall chemistry must not be overlooked. 

 There is a further consideration which concerns the 

 exact role of the extraneuronal elements of neural 

 tissue. As long as the mechanism of excitation and 

 conduction remains a problem, the question of the 

 extent of involvement of the neuroglial elements will 

 remain open. For this reason it is equally as dangerous 

 to exclude the neuroglia from a discussion of 

 'neuronal' chemistry as it is to interpret the chemistry 

 of neuronal function on the basis of the chemistrv 

 of the heterogeneous complex of the nervous system. 

 The need for distinguishing the metabolism and 

 chemistry of the functional elements from the merely 

 structural or passive components is tantamount to an 

 understanding of the relationship of chemistrv to 

 function. In many species and under certain con- 

 ditions the evidence that the neuron itself is auton- 

 omously functional in excitation is overwhelming, 

 so that some justification does exist for studying 

 'neuronal chemistry' per se. 



It seems highly improbable, however, that the role 

 of the neuroglial elements is a purely 'passive' one. 

 Early in this century Nageotte (87) suggested that 

 the function of the neuroglia was a nutritive one 

 insofar as it appeared to contain secretory granules. 

 A similar view still obtains today, particularly in 

 regard to invertebrate nerves where the nutritional 

 state of the neurons is correlated with the density of 

 secretion granules within the neuroglia, a function 

 which may be of special significance since blood 



18, 5 



