Actions of the antidepressant drug imipramine on the voltage-clamped Myxicola giant axon

Abstract

The effects of the antidepressant drug imipramine were studied on the voltage-clamped Myxicola giant axon at concentrations from 10- minus 6 to 5 X 10- minus 5 M. Over this range, imipramine reversibly reduced both the sodium and potassium conductances without having any substantial effect on either the resting membrane potential or the leakage conductance. The observed dose-response relation is described by a Langmuir adsorption isotherm with an apparent dissociation constant of 9 X 10-minus 6 M. The sodium and potassium conductance-voltage curves are shifted in the hyperpolarizing direction along the voltage axis, the magnitude of the displacement increasing with increasing concentrations of imipramine. There was no significant effect of imipramine on either time to peak sodium current or time to half-maximum steady-state current.