The action of botulinum A neurotoxin on the inhibition by antidromic stimulation of the lumbar monosynaptic reflex.

1. Botulinum toxin type A was injected into gastrocnemius muscles of cats and 2 days later its action on the monosynaptic gastrocnemius reflex and on the recurrent inhibition was investigated. 2. In early local botulism, no significant change in the monosynaptic gastrocnemius reflex was observed. 3. The inhibition by antidromic stimulation of the monosynaptic gastrocnemius reflex was significantly reduced. 4. During the early phases of local botulism an action of botulinum toxin on parts of the soma membrane of the alpha-motoneuron is suggested.