^6 BIOCHIMICA ET BIOPHYSICA ACTA VOL. 4 (1950) 



STUDIES ON PERMEABILITY IN RELATION TO NERVE FUNCTION 



II. IONIC MOVEMENTS ACROSS AXONAL MEMBRANES* 



by 



M. A. ROTHENBERG** 

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



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



INTRODUCTION 



The ionic concentration gradients which exist between the inside and the outside 

 of nerve fibres and their possible role in nerve function have been discussed in the preced- 

 ing paper. In spite of the importance of this question very little information is available 

 as to the ionic movements across axonal surface membranes in rest and during activity. 

 The investigations on the giant axon of Squid have demonstrated that this material is 

 most suitable for permeability studies. With the increased availability of radioactive 

 ions from the Oak Ridge pile a more direct approach to the problem became feasible. 

 It was thought that precise and more quantitative data might be obtained by subjecting 

 the giant axon of Squid, Loligo peallii, to artificial environments in which all or part of 

 a given ionic constituent was replaced in isomolar concentration with its radioactive 

 isotope. 



METHODS 



Chemical. Na^* and K'*^, available from the Oak Ridge pile in the form of the carbonates, were 

 dissolved in the smallest possible volume of distilled water and then converted to the chlorides by 

 the addition of equivalent quantities of dilute HCl. Aliquots of the neutral solution were then trans- 

 ferred to tared vials and evaporated to dryness under infra-red heating lamps. The quantity of salt 

 per vial was determined by weighing and artificial sea water was prepared from these as described 

 below. All necessary precautions were maintained {i.e., remote control pipetting behind thick lead 

 shields, etc.) in carrying out the conversions of carbonates to chlorides***. 



The Ca*^ employed in our earliest experiments was that obtained from the Oak Ridge pile in 

 the form of CaCOg (AEC Catalog Item 41= 13 A). Since this material contained A'' in addition to 

 Ca*^, it was deemed necessary to pump out the A^' under high vacuum before carrying out the con- 

 vei'sion of the carbonate to chloride. In general, the latter conversion was carried out in a manner 

 similar to that for Na^"* and K*^ above. In later experiments, high specific acitivity Ca*^ was employed 



* These investigations were supported by a research grant from the Atomic Energy Commission. 

 From a dissertation submitted in partial fulfilment of the requirements for the degree of 

 Doctor of Philisophy in the Faculty of Pure Science of Columbia University. 



*** We are indebted to Tracerlab, Inc., Boston, Mass., for carrying out the carbonate to 

 chloride conversions. 



References p. 114. 



