What is the mechanism of action of onabotulinumtoxin A in migraine prophylaxis?

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Multiple Choice

What is the mechanism of action of onabotulinumtoxin A in migraine prophylaxis?

Onabotulinumtoxin A works by blocking the release of neurotransmitters from presynaptic nerve terminals. The toxin binds to nerve endings, is taken into the cell, and its light chain cleaves SNARE proteins (such as SNAP-25). This prevents vesicles from fusing with the membrane, so acetylcholine cannot be released into the synapse, which reduces muscle activity. In migraine prevention, this same mechanism also lowers the release of pain mediators from sensory neurons in the trigeminal system, helping to reduce peripheral sensitization and frequency of attacks. This description fits best because it captures the main action—inhibiting acetylcholine release to lessen neural signaling and muscle activity. It’s not about inhibiting acetylcholine synthesis, nor about increasing release, and it’s not a blocker of voltage-gated sodium channels.

Onabotulinumtoxin A works by blocking the release of neurotransmitters from presynaptic nerve terminals. The toxin binds to nerve endings, is taken into the cell, and its light chain cleaves SNARE proteins (such as SNAP-25). This prevents vesicles from fusing with the membrane, so acetylcholine cannot be released into the synapse, which reduces muscle activity.

In migraine prevention, this same mechanism also lowers the release of pain mediators from sensory neurons in the trigeminal system, helping to reduce peripheral sensitization and frequency of attacks.

This description fits best because it captures the main action—inhibiting acetylcholine release to lessen neural signaling and muscle activity. It’s not about inhibiting acetylcholine synthesis, nor about increasing release, and it’s not a blocker of voltage-gated sodium channels.

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