Iodoacetate depression in Xenopus sciatic single nerve fibers

¹ Department of Physiology, Washington University School of Medicine, Saint Louis, Missouri

Under conditions of continuous fluid exchange at a pH 7.55, a 10-min exposure of Xenopus sciatic single nerve fibers to iodoacetate results in eventual decline in the maximum rate of change of membrane potential, even after a delay of an hour or more during which no changes are apparent. This delayed effect is obtained over an iodoacetate concentration range of 0.1–20.0 mm sodium iodoacetate. Neither the resting membrane potential nor the maximal limiting response obtained during hyperpolarization are affected at a time when iodoacetate has appreciably depressed the spike in the nonpolarized fiber. These findings are taken to indicate that iodoacetate blocks a chain of reactions at a link remote from the process directly concerned with maintenance of the resting level of the sodium conductance. Neither lactate nor pyruvate can be relied on to bring about recovery from the iodoacetate depression.

Key Words: iodoacetate depression of nerve • metabolism and sodium conductance • dependence of action potential on metabolism

Submitted on September 28, 1964