Chemically induced myotonia in amphibia.

Frogs and toads treated with high doses of anthracene-9-carboxylic acid (A-9-C) develop prolonged muscular contractions and 'divebomber' electromyograms characteristic of myotonia. Hitherto, myotonia has been considered peculiar to homeotherms where it is associated with several hereditable diseases and can be induced by specific treatments, most of which seem to act by decreasing membrane chloride conductance. Our work indicates that myotonia can be induced in amphibia by similar means. We offer possible reasons why others have missed seeing myotonia in amphibia.