Which toxin blocks the release of acetylcholine at the neuromuscular junction, causing paralysis?

Which toxin blocks the release of acetylcholine at the neuromuscular junction, causing paralysis?

• A. Diphtheria toxin
• B. Botulinum toxin
• C. Cholera toxin
• D. Tetanus toxin

Answer: (B)

At the neuromuscular junction, muscle contraction depends on acetylcholine being released from the nerve ending to activate receptors on the muscle fiber. Botulinum toxin cuts SNARE proteins essential for vesicle fusion, so acetylcholine cannot be released. Without acetylcholine, the muscle fiber can’t be activated, leading to flaccid paralysis. This differs from tetanus toxin, which causes spastic paralysis by blocking the release of inhibitory neurotransmitters in the CNS; diphtheria toxin stops protein synthesis, and cholera toxin raises cAMP causing diarrhea rather than NMJ paralysis.

At the neuromuscular junction, muscle contraction depends on acetylcholine being released from the nerve ending to activate receptors on the muscle fiber. Botulinum toxin cuts SNARE proteins essential for vesicle fusion, so acetylcholine cannot be released. Without acetylcholine, the muscle fiber can’t be activated, leading to flaccid paralysis. This differs from tetanus toxin, which causes spastic paralysis by blocking the release of inhibitory neurotransmitters in the CNS; diphtheria toxin stops protein synthesis, and cholera toxin raises cAMP causing diarrhea rather than NMJ paralysis.