The distribution of potassium and leakage channels in rat myelinated axons.

Abstract

Frankenhaeuser and Huxley (1964) attributed a large ohmic leakage conductance to the frog node of Ranvier, and this assumption has been accepted for most voltage-clamp studies. Barrett and Barrett (1982), however, proposed a different equivalent circuit, in which much of the leakage current flowed under or through the myelin sheath, rather than across the nodal membrane. Baker et al. (1987) made recordings of electrotonus in rat spinal root axons poisoned with tetrodotoxin (TTX), which they interpreted in terms of Barrett and Barrett's model. I have now simulated those recordings of electrotonus, using a computer model of a node and internode with the equivalent circuit shown in Fig. 1.