EFFECTS OF QUATERNARY AMMONIUM IONS ON A CRUSTACEAN NERVE-MUSCLE PREPARATION

¹ Departments of Pharmacology, New York University School of Medicine and Cornell University Medical College, New York, New York

Several ethonium ions were shown to increase the neurally evoked contractile response of crayfish skeletal muscle; this same action has been observed in mammalian nerve-muscle preparations.

Replacement of one ethyl group in the onium center of these ions by a methyl group converts the compound into one which depresses the crayfish contractile response.

Stimulation of the motor axon proximally to a drug-treated segment also resulted in potentiation of the contractile response. The drug concentrations required to produce this effect were significantly higher than those which increased contraction after perfusion through the propodite.

It is suggested that the potentiating action of ethonium ions on both mammalian and crayfish contractile response is related to an effect on the motor axon terminals.