The effect of sea anemone toxins from Parasicyonis actinostoloides and Anemonia sulcata on the Na conductance in crayfish giant axons was studied under voltage-clamp conditions. The toxin slowed the Na inactivation process without changing the kinetics of Na activation or K activation in an early stage of the toxin effect. An analysis of the Na current profile during the toxin treatment suggested an all-or-none modification of individual Na channels. Toxin-modified Na channels were partially inactivated with a slower time course than that of the normal inactivation. This slow inactivation in steady state decreased in its extent as the membrane was depolarized to above -45 mV, so that practically no inactivation occurred at the membrane potentials as high as +50 mV. In addition to inhibition of the normal Na inactivation, prolonged toxin treatment induced an anomalous closing in a certain population of Na channels, indicated by very slow components of the Na tail current. The observed kinetic natures of toxin-modified Na channels were interpreted based on a simple scheme which comprised interconversions between functional states of Na channels. The voltage dependence of Parasicyonis toxin action, in which depolarization caused a suppression in development of the toxin effect, was also investigated.
Article| March 01 1983
Effect of sea anemone toxins on the sodium inactivation process in crayfish axons.
Online Issn: 1540-7748
Print Issn: 0022-1295
J Gen Physiol (1983) 81 (3): 305–323.
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A Warashina, S Fujita; Effect of sea anemone toxins on the sodium inactivation process in crayfish axons.. J Gen Physiol 1 March 1983; 81 (3): 305–323. doi: https://doi.org/10.1085/jgp.81.3.305
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