How Does the Botulinus Toxin Decrease the Effect of a Neurotransmitter?

Published July 21, 2010

Question by Mike: How does the botulinus toxin decrease the effect of a neurotransmitter?
A- The toxin blocks the release of the neurotransmitter.
B- The toxin blocks the reuptake of the neurotransmitter at the presynaptic membrane.
C- The toxin blocks the action of the neurotransmitter at the postsynaptic membrane.

Thanks ..

Best answer:

Answer by eli
The heavy chain of the toxin is particularly important for targeting the toxin to specific types of axon terminals. The toxin must get inside the axon terminals in order to cause paralysis. Following the attachment of the toxin heavy chain to proteins on the surface of axon terminals, the toxin can be taken into neurons by endocytosis. The light chain is able to cleave endocytotic vesicles and reach the cytoplasm. The light chain of the toxin has protease activity. The type A toxin proteolytically degrades the SNAP-25 protein, a type of SNARE protein. The SNAP-25 protein is required for vesicle fusion that releases neurotransmitters from the axon endings (in particular Acetylcholine) The toxin cleaves these SNAREs, preventing vesicles from fusing with the membrane to release.

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