杏吧原创

A WOMAN who spent a month in a cage full of scorpions and survived their
stings was protected by the very toxins that make the sting so painful.

Last month, Nor Malena Hassan spent a record-breaking 30 days in a glass cage
with 2700 black scorpions in the town of Kota Baru in Malaysia. She was stung
seven times, but survived.

Now Hoon-Eng Khoo and his team at the National University of Singapore have
analysed venom from the black scorpion Heterometrus spinifer. They found that
the venom constricts blood vessels. This stops venom spreading through the body,
so the stings only cause localised pain.

鈥淭he scorpion woman did receive painful stings, but as we鈥檝e shown, the genus
Heterometrus is unlikely to contain any potent neurotoxins,鈥� says Khoo. 鈥淪o she
was in no mortal danger.鈥�

Khoo鈥檚 team found that the active substances in black scorpion venom are
acetylcholine and noradrenaline, two neurotransmitters found in mammals.
Acetylcholine shuttles nerve signals from one cell to the next. The venom
contains so much of it that it overstimulates nerve cells, causing intense
pain.

Noradrenaline probably intensifies the pain by trapping the acetylcholine.
But to do this it constricts blood vessels, stopping the venom from spreading
further and protecting the victim, Khoo says. The findings, to be published in a
forthcoming issue of the journal Biochemical Pharmacology, suggest that
Heterometrus uses its sting primarily to defend itself rather than to paralyse
or kill prey.

There are 1050 known species of scorpion. Most, like H. spinifer and its
relatives, are relatively harmless. Only the most dangerous, such as the Chinese
Buthus martensii Karsch, have venom that spreads through the body. This causes
an overwhelming cascade of nerve signalling that can lead to heart failure or
respiratory collapse.