The effects of the subcutaneous injection of the crude venom of the Australian common brown snake, Pseudonaja textilis on the skeletal neuromuscular system.

1 The effects of the crude venom of the Australian common brown snake on the mammalian neuromuscular system have been investigated. 2 The venom was injected subcutaneously into the dorso-lateral aspect of one hind limb of the rat. The limb was paralyzed within 90 min and remained paralysed for 2 to 3 days. 3 The exposed muscles failed to respond to indirect excitation, and individual fibres were not depolarized at the nerve-muscle junction by exposure to carbachol. 4 The wet weight, histological appearance, resting potential and input resistance of the muscle fibres and their ability to generate directly elicited action potentials were unaffected by exposure to the venom. 5 Administration of venom to isolated preparations caused a reduction in the amplitude of miniature endplate potentials, with no change in frequency. The quantal content of evoked endplate potentials was unchanged. 6 It was concluded that the crude venom was largely devoid of presynaptic activity and myotoxicity, and that its primary site of neurotoxicity was directed to the postsynaptic membrane.