The optimum density of sodium channels in an unmyelinated nerve

In introducing this meeting I wish to refer to a theoretical development which may be relevant to some of our discussion. Present estimates suggest that the density of sodium channels varies between 2.5/(xm2 in the 0.2 pirn diameter axons of the olfactory nerve of the garfish (Colquhoun, Henderson & Ritchie 1972) to about 500/pim2 in the giant nerve fibres of the squid (Keynes & Rojas 1974). Since giant nerve fibres are considered to be an adaptation to rapid movement it is of interest to consider whether there is an optimum density of sodium channels at which conduction velocity is maximal. If this can be established it is then important to develop methods for calculating the optimum density on different sets of assumptions.