24 : 5/ The Molecular Basis of Nerve Conduction 



457 



presented in more detail in the references at the end of the chapter. 

 The results emphasize both the importance of the clamped nerve 



100 



E 



- so 



100 

 3 50 



r 110 mv 



0L 



2 msec 



Figure II. Predicted and observed action potential, (a) 

 shows the curve predicted by equations developed in this 

 section, whereas (b) is a tracing of an actual action potential 

 observed on an axon. After A. L. Hodgkin and A. F. Huxley, 

 "A Quantitative Description of Membrane Current and its 

 Application to Conduction and Excitation in Nerve," J. Physiol. 

 117: 500 (1952). 



experiments and the significance of the minimum of six rate constants 

 found. 



5. Summary 



The equations and experiments of Hodgkin and Huxley have been 

 checked by other investigators and found essentially correct. These 

 equations rule out all previous molecular models and they rule out 

 passive diffusion of Na + ions. However, the equations cannot supply 

 any model related to known molecules. 



One could fit the acetylcholine activity into these equations by per- 

 mitting ACh to react with a variety of molecules in the membrane 

 having a variety of effects. To do this, one has to produce a mysterious 

 (that is, unknown) mechanism for releasing an amount of ACh which is 

 a complex function of the membrane potential. Although Nachman- 

 sohn's conclusions, that is, ACh and cholinesterase are necessary for the 

 conduction of spike potentials in axons, appear quite justified, the work 

 of Hodgkin and Huxley makes it clear that these can be but two of a 

 number of molecules necessary to explain the action of the neuron 

 membrane. 



