acetylcholine release

Class

botulinum toxin type A

Acetylcholine release is the process by which a nerve terminal secretes acetylcholine, a chemical messenger that activates skeletal muscle and regulates several autonomic functions, including salivary and sweat-gland secretion. Botulinum toxin type A is a biologic protein that inhibits this release at peripheral cholinergic nerve endings. Its light-chain component enters the nerve terminal and cleaves SNAP-25, a protein required for the SNARE complex that normally enables synaptic vesicles to fuse with the cell membrane. As a result, acetylcholine-containing vesicles cannot be released efficiently.

Local reduction of acetylcholine signaling produces temporary weakening of overactive muscles or reduced activity of cholinergically controlled glands. This mechanism is relevant to disorders involving focal muscle overactivity, such as dystonia and spasticity, and to conditions involving excessive glandular secretion, such as sialorrhea and hyperhidrosis. It also has applications in selected pain and bladder disorders in which local nerve signaling contributes to symptoms. The effect is localized when administration is appropriately targeted, but it can extend beyond the intended site if toxin activity or injected material reaches adjacent tissues. Important on-target trade-offs therefore include unwanted muscle weakness, swallowing difficulty, dry mouth, or other changes in autonomic function.