Abstract
Botulinum toxin (BoTx) was injected into the muscles of 1 leg in mice, causing local paralysis. Black widow spider venom (b.w.s.v.) was then injected into the paralyzed muscles 3 or 15 days later. In both groups b.w.s.v. destroyed the nerve terminals poisoned by ToTx. In the 15 days group axonal sprouts, which had formed due to the block of neuromuscular transmission by BoTx, were also destroyed. Within a few days the motor nerve terminals regenerated and the muscles recovered from paralysis at a faster rate than after BoTx alone. Recovery seemed to begin earlier in muscles where axonal sprouting was already advanced when b.w.s.v. was injected. The normal pattern of innervation was re-established in both groups, which was in marked contrast with muscles after BoTx alone where numerous sprouts and many ectopic end-plates had formed.