Botox and pain

This is a bit old, but still interesting.

Combining the most potent neurotoxin known to man and a protein from the Mediterranean coral tree could deliver a long-lasting treatment for the chronic pain that afflicts millions of people, including cancer patients.

The neurotoxin in question is botulinum toxin, perhaps better known as Botox ....The neurotoxin, whose effects can last for months, works by blocking the release of the neurotransmitters that relay the "contract now" message from nerves to muscles. The machinery that is knocked out is actually found inside most cells, but the toxin only affects the neurons that control muscles. This is because of a targeting sequence in the toxin that only permits it to bind to muscle cells.

So Keith Foster's team at the Centre for Applied Microbiology and Research near Salisbury, UK, went looking for a targeting sequence specific to the nerves that transmit pain signals. He wanted to use this sequence to turn the neurotoxin into a painkiller. They found it in the Mediterranean coral tree, Erythrina cristagalli.

It may be a complete coincidence that the coral tree protein binds to the surface of pain neurons and no other cells, but all that matters to Foster is that it does. Since pain nerves do not carry any other sort of message, the altered toxin his team has created stops pain without affecting touch, for example

Results from tests in mice have been impressive. In three experiments, Foster's painkiller performed as well as morphine at preventing pain. But it was still working nine days later, whereas morphine would have worn off after four hours.