Neurophysiological effects of insecticidal pyrethroids and methoxychlor and of the anticalmodulin agent W-7

Abstract 1. W-7, an anticalmodulin agent, prolonged the falling phase of the action potential in crayfish ( Procambarus clarkii ) giant axons, as did meta -methylbenzyl pyrethrate, a pyrethroid insecticide, and the methoxychlor of a DDT analog. 2. The anticalmodulin agent suppressed both the inward and outward membrane currents in the axon, measured under voltage-clamp conditions. 3. The pyrethroid and methoxychlor insecticides induced a large inward tail-current upon step repolarization, but the anticalmodulin agent did not induce a current of a detectable size.