Potassium channels in the nodal membrane of rat myelinated fibres

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Abstract
Mammalian fibers from rabbit and rat were successfully studied in detail by means of the voltage clamp. The early transient or Na+ conductance system was similar to that in frog and squid axons. The delayed conductance or K+ currents were negligible. Only after chemical and osmotic manipulations, which were said to expose channels buried under the myelin, did Chiu and Ritchie find delayed currents in rabbit fibers. If confirmed, this would mean that the membrane conductance system of mammalian fibers is so different from that of invertebrate and amphibian axon models as to make the data base gathered from amphibian myelinated fibers (frog and toad) and invertebrate giant axons (squid and Myxicola) irrelevant to human and other mammalian fibers. It is possible to find in the normal nodal membrane of rat myelinated fibers K+ currents that flow through channels which are similar in many respects to those found in the frog node or squid axons.