The Botulinum Toxin as a Therapeutic Agent: Molecular Structure and Mechanism of Action in Motor and Sensory Systems

Botulinum neurotoxin (BoNT) produced by Clostridium botulinum is the most potent molecule known to mankind. Higher potency of BoNT is attributed to several factors, including structural and functional uniqueness, target specificity, and longevity. Although BoNT is an extremely toxic molecule, it is now increasingly used for the treatment of disorders related to muscle hyperactivity and glandular hyperactivity. Weakening of muscles due to peripheral action of BoNT produces a therapeutic effect. Depending on the target tissue, BoNT can block the cholinergic neuromuscular or cholinergic autonomic innervation of exocrine glands and smooth muscles. In recent observations of the analgesic properties of BoNT, the toxin modifies the sensory feedback loop to the central nervous system. Differential effects of BoNT in excitatory and inhibitory neurons provide a unique therapeutic tool. In this review the authors briefly summarize the structure and mechanism of actions of BoNT on motor and sensory neurons to explain its therapeutic effects and future potential.