The role of diffusion barriers in determining the excitability of peripheral nerve.

The excitability changes occurring in normal isolated peripheral nerves of rats have been studied during exposure to hypoxic and anoxic conditions before and after the administration of insulin. The changes observed have been explained in terms of the dynamics of K' equilibrium in the periaxonal spaces, and attention is drawn to the importance of the relative impermeability of the periaxonal diffusion barrier in determining this equilibrium. Isolated peripheral nerves from alloxan-diabetic rats, studied under similar conditions, show significant differences in the sequence of their excitability changes. It has been shown that the rate of change of excitability in these nerves is slower than those of control nerves. These results have now been interpreted in terms of the K' changes in the periaxonal space. It is concluded that these slower excitability changes are due to an increase in the permeability of the diffusion barrier of the diabetic nerve to potassium.