botulinal toxin

botulinum toxin, botulinus toxin an exotoxin produced by germinating spores and growing cells of Clostridium botulinum. The toxin binds to presynaptic terminals of the central nervous system and blocks the release of acetylcholine, leading to paralysis. There are seven immunologically distinct types (A–G). Type A is one of the most powerful poisons known; it is also used therapeutically by injection to inhibit muscular spasm in the treatment of dystonic disorders such as blepharospasm and strabismus, to treat wrinkles of the upper face, and to reduce anal sphincter pressure to promote healing of chronic anal fissure. Type B is used therapeutically by injection in the treatment of cervical dystonia. See also botulism.