78 BIOCHIMICA ET BIOPHYSICA ACTA VOL. 4 (l950)' 



STUDIES ON PERMEABILITY IN RELATION 

 TO NERVE FUNCTION 



I. AXONAL CONDUCTION AND SYNAPTIC TRANSMISSION 



by 



DAVID NACHMAXSOHN 



Department of Neurology, College of Physicians and Surgeons, Columbia University, 



New York, N.Y. (U.S.A.) 



INTRODUCTION 



Cellular boundaries are endowed with the ability either to permit or to prevent the 

 entrance and leakage of various compounds and metabolites. This makes possible the 

 elimination of waste products and the supply of substances important for ionic equi- 

 librium, energy requirements, and other vital functions of the cell. There are many 

 indirect indications for the selective permeability of the membranes covering the cell. 

 The g'eat importance of this property for the understanding of cellular mechanisms and 

 of the action of compounds applied externally, which includes most pharmacolog'cal 

 effects, has long been recognized. Nevertheless, surprisingly little is known in regard to 

 the factors wh'ch determine and affect permeability of cellular boundaries. Direct 

 measurements are extremely difficult. The introduction of isotopes as research tool in 

 biology, mainly due to the work of Hevesy^ and Schoenheimer and Rittenberg^, 

 has opened a new pathway to the approach of the problem, but the obstacles to be 

 overcome are still tremendous. The lucid appraisal of the field by Krogh^ in his Croonian 

 lecture shows that in spite of some progress in recent years this aspect of cellular function 

 is in its initial phase. 



The permeability of the surface membranes of the nerve cell is of particular interest. 

 Physiologists of the last century have already postulated that changes in permeability 

 must be intimately assoc'ated with the function of the neuron, i.e., with the propagation 

 of the nerve impulse. Du Bois-Reymond who first established conclusively that nerve 

 activity is associated with flow of current devoted much time to testing the possibility 

 that the source of the electromotive force for the electrical manifestations observed may 

 be ionic concentration g-adients between the interior of the cell and its outer environ- 

 ment*. When, in the later part of the nineteenth century, physico-chemical invest'gations 

 revealed the marked potential differences whxh may be produced by semipermeable 

 membranes, the existence of such membranes was postulated as a basis for the electrical 

 manifestations during the passage of the nerve impulse. Ostwald^ wrote in iSgo: "An 

 den halbdurchlassigen Membranen kommen weit grossere Potentialdifferenzen zustande 

 als in gewChnlichen Flussig'ceitsketten. Es ist vielleicht nicht zu gewagt schon hier die 

 Vermutung auszusprechen , dass nicht nur die Strome in Muskeln und Nerven sondern 

 auch namentlich die ratselhaften Wirkungen der elektrischen Fische durch die hier 

 References p. 93I95. 



