The neurotoxicity of the venom phospholipases A(2), notexin and taipoxin

The presynaptically active, toxic phospholipases known as notexin and taipo xin are principal components of the venom of the Australian tiger snake and the Australian taipan respectively. The inoculation of the toxins into one hind limb of rats caused, within 1 h, the depletion of transmitter from th e motor nerve terminals of the soleus muscle. This was followed by the dege neration of the motor nerve terminals and of the axonal cytoskeleton. By 24 h 70% of muscle fibers were completely denervated, Regeneration and functi onal reinnervation were almost fully restored by 5 days, but collateral inn ervation was common in the regenerated muscles, and this abnormality persis ted for at least 9 months. The data provide an explanation for both the sev erity of neuromuscular paralysis that can accompany envenoming bites by tig er snakes and taipans and the difficulty experienced by physicians in manag ing the envenomed subjects. (C) 2000 Academic Press.