Which of the following best describes the mechanism of Botulinum toxin?

Which of the following best describes the mechanism of Botulinum toxin?

• A. Stimulates dopamine release
• B. Inhibits acetylcholine release at the neuromuscular junction
• C. Inhibits GABA activity
• D. Increases acetylcholine release

Answer: (B)

Botulinum toxin works by blocking communication between nerve and muscle. It is a protease that cleaves SNARE proteins needed for acetylcholine-containing vesicles to fuse with the nerve terminal membrane, so acetylcholine cannot be released at the neuromuscular junction. With no acetylcholine to stimulate the muscle, motor neurons cannot trigger contraction, leading to flaccid paralysis. This explains why it relaxes overactive muscles and is used clinically for cosmetic and therapeutic purposes. The other ideas don’t fit because botulinum toxin does not stimulate dopamine release, does not inhibit GABA, and does not increase acetylcholine release; it inhibits its release instead.

Botulinum toxin works by blocking communication between nerve and muscle. It is a protease that cleaves SNARE proteins needed for acetylcholine-containing vesicles to fuse with the nerve terminal membrane, so acetylcholine cannot be released at the neuromuscular junction. With no acetylcholine to stimulate the muscle, motor neurons cannot trigger contraction, leading to flaccid paralysis. This explains why it relaxes overactive muscles and is used clinically for cosmetic and therapeutic purposes. The other ideas don’t fit because botulinum toxin does not stimulate dopamine release, does not inhibit GABA, and does not increase acetylcholine release; it inhibits its release instead.