Motor end-plates in regenerating rat skeletal muscle exposed to botulinum toxin.

Botulinum toxin type A, when applied to the extensor digitorum longus muscle of rats, reduces spontaneous and evoked transmitter release to a few per cent of the normal level. The toxin, however, fails to affect the morphological redifferentiation of the postsynaptic part of the neuromuscular junction following muscle degeneration-regeneration induced by a selective myotoxic agent, bupivacaine. This indicates that neither transmitter release nor resulting muscle activity are necessary for the differentiation of the sole plate.