EFFECT OF SCORPION VENOM ON IONIC CURRENTS OF NODE RANVIER .I. PERMEABILITIES PNA AND PK

1. The action of scorpion venom (10-6 g/ml) on the ionic currents of single myelinated nerve fibres of Xenopus laevis was studied in voltage clamp experiments. 2. Scorpion venom was found to affect the sodium permeability as well as the potassium permeability of the nodal membrane. 3. The main effects of scorpion venom on the sodium permeability PNa are: a) The maximum sodium permeability {Mathematical expression} is reduced to 60% of its value in the unpoisoned membrane. b) The sodium inactivation is markedly slowed and proceeds in two phases. c) The time course of PNa can be described assuming that the variable h is the sum of two components x and y, whose time constants τx and τy are 4 and 200 times τh of the unpoisoned membrane. 4. The effects of scorpion venom on the potassium permeability PK are: a) The maximum potassium permeability PK' is reduced to about 35% of its normal value. b) The increase of PK' upon depolarisation is slowed down; two phases can be distinguished. 5. The effects on sodium inactivation and potassium permeability may explain the extreme prolongation of the action potential under the influence of scorpion venom. © 1968 Springer-Verlag.