EFFECT OF TEMPERATURE ON SLOWLY CHANGING SODIUM PERMEABILITY OF VERATRINIZED NODES OF RANVIER

1. The effect of veratridine-Ringer (10-5 g/ml; pH 8.1) of varying temperature on single nodes of Ranvier of frog motor fibres was studied by means of the double air gap method. 2. Nodes, once depolarized by veratridine at room temperature, repolarized or even hyperpolarized on cooling. The change in membrane potential markedly out-lasted the change in temperature. 3. Voltage clamp experiments revealed that repolarization was caused by a reduction of Ps, the veratridine-induced, slowly changing Na permeability. The Q10 of the steady state value of Pswas 3.3 between 8 and 22°C. 4. Cooling considerably increased the time constant, τs, with which Pschanged on sudden displacement of membrane potential. The Q10 of 1/τs was 3.9 between 8 and 23°C. 5. Fast changes in temperature induced steps in membrane current which were followed by slower phases of current change. A hypothesis is offered to explain these changes and the unusually high temperature coefficient of the stationary value of Ps. © 1969 Springer-Verlag.