Pharmacological properties of axonal sodium channels in the cockroach Periplaneta americana L. II. Slowing of sodium current turn-off by Condylactis toxin.

Condylactis toxin induces a prolonged falling phase in action potentials recorded from giant axons of the cockroach Periplaneta americana L. A distinct plateau potential can be recorded in the presence of Condylactis toxin at concentrations of 0.5 mg/ml and above. In cockroach axons, voltage-clamp experiments show that Condylactis toxin acts primarily by slowing the sodium current turn-off without affecting either the time-course of the sodium conductance increase or the peak amplitude of the transient sodium current.