Biomedical aspects of Botulinum Toxin

Abstract

Clostridium botulinum produces a potent neurotoxin, which causes the neuroparalytic illness in humans and animals known as botulism. Seven immunologically distinct neurotoxins are recognized, which are designated by the letters A through G. the different serotypes of botulinum toxin vary in the animal species that they affect and the severity and duration of paralysis that they evoke. Botulinum toxin type A has become an important pharmaceutical for the treatment of segmental movement disorders, spasticity, pain syndromes, and various other neuronal disorders. Botulinum toxin specifically and tightly binds to cholinergic neurons. Upon endocytosis and internalization into the nerve terminal, the toxin acts to block or slow the exocytotic release of neurotransmitters, particularly acetylcholine. Selective injection of botulinum toxin into neuromuscular regions produces a local weakening of proximal muscles and relief from excessive involuntary muscle contractions In addition to directly affecting cholinergic neurotransmission, botulinum toxin also exerts other poorly understood effects including altering activity of autonomic ganglia. the outstanding properties of botulinum toxin as a pharmacological agent are its specificity for peripheral nerves and its long duration of action Complications and drawbacks of botulinum toxin therapy include immunologic resistance in some patients and diffusion and resulting ptosis of neighboring muscles. these side effects can be avoided by proper purification and preparation of the toxin for pharmaceutical use.