channels prevents neurons from sending signals. Numbness occurs
because signals from sensory neurons in the skin do not reach the
brain. And signals from the brain don’t reach the muscles, so the
experience after TTX ingestion is one of muscle weakness, difficulty
moving, and shortly thereafter paralysis—including the muscles
controlling breathing. So, if someone dies from TTX poisoning, as
occasionally happens, it is from respiratory paralysis and the result-
ing suffocation. There is no chemical antidote to TTX poisoning.
However, its effect on sodium channels is not permanent. The TTX
molecule sticks to a channel only temporarily, eventually falls off, and
is washed out of the body. Thus, if a person who has been poisoned
with TTX can be mechanically respirated during the period of paraly-
sis—up to several hours—they will survive the ordeal.
Two other interesting things may be noted about the poisonous
effects of TTX. First, the heart does not stop beating—the Na* chan-
nels in the heart are of a sufficiently different molecular type that they
are not blocked by TTX. Second, the brain is not affected—the ability
of nerve cells in the brain to send signals is not impaired. Why not?
Because TTX does not enter the brain! This brings us to the concept of
the blood-brain barrier.
Cells of the blood-vessel wallBody Brain
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