The effects of neurotoxins and radiation on the neuromuscular junction of the mouse: a physiological and morphological study

Some of the factors controlling axonal growth are studied by observing the effects of botulinum toxin, black widow spider venom and X-irradiation on teh neuromuscular junction in mice. Irradiation alone caused no changes since radiation is believed to affect only the Schwann cells. Irradiation prior to the administration of botulinum delayed the recovery of transmission and led to the failure of maturation and myelination of newly formed axons; this illustrates the importance of the Schwann cell for continued growth, functional maturation and myelination of axons. The effect of black widow spider venom on the end-plates was degeneration of the nerve terminals within a few hours but after a few days there was regeneration and restoration of normal transmission. The effects of black widow spider venom on muscles paralysed by botulinum were also studied; the recovery from the action of botulinum was greatly accelerated by the venom and axonal sprouting was either abolished or greatly reduced. (U.K.)