Pharmacology of the venom of the gastropod Conus magus

Abstract

The venom of Conus magus has a direct action on vertebrate skeletal and cardiac musculature. With vertebrate skeletal musculature a sustained contracture associated with a progressive loss of response to stimulation was elicited by the venom. Isolated mammalian hearts responded to the venom by a marked increase in the amplitude of the contraction cycle. Mammalian extravascular smooth musculature responded to the venom with a sustained contracture but no response was elicited by the venom in vascular smooth musculature or in barnacle musculature. Trains of impulses were generated by the venom in vertebrate motor fibres. The compound action potential exhibited by amphibian sciatic nerve declined slowly and conduction in the nerve was ultimately blocked by high concentrations (100 μg per ml) of venom. Activity of the venom in vertebrate striated muscle fibres is dependent on the existence of a polarized fibre membrane. Transmembrane resting potentials of individual skeletal muscle fibres exposed to adequate concentrations of the venom fell quickly, the extent of the fall being directly related to venom concentration. The venom caused initially a marked increase in ion flux across the short-circuited frog skin. Evidence was obtained which indicated that the venom affected movements of sodium ions across the sarcolemma.