EFFECTS OF STONEFISH (SYNANCEIA-TRACHYNIS) VENOM ON MURINE AND FROG NEUROMUSCULAR-JUNCTIONS

The neuromuscular toxicity of stonefish Synanceia trachynis) venom was characterized by electrophysiological and electron microscopic examination of isolated murine and frog nerve-skeletal muscle preparations exposed to various concentrations of venom. Low concentrations of venom (2.5-10 mug/ml) acted presynaptically by causing release and depletion of neurotransmitter from the nerve terminal. The response was Na+ channel-independent (resistant to tetrodotoxin), required the presence of either Ca2+ or Mg2+, and was observed with botulinum neurotoxin-paralyzed nerve-muscle preparations. Higher concentrations of venom (100-300 mug/ml) acted postsynaptically and presynaptically. They caused irreversible depolarization of muscle cells and microscopically observable muscle and nerve damage. We conclude that the previously observed neuromuscular toxicity of stonefish venom is a consequence of the venom's dose-dependent, presynaptic and postsynaptic actions at the myoneural junction.