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Thursday, November 25, 2010

Finding a pain gene

An international team of scientists has identified a gene that is implicated in the sensation of pain. In particular, this gene allows both insects and mammals to sense dangerous levels of heat.

In an attempt to find genes involved in feeling pain, the researchers altered nearly 12,000 fruit fly genes, and then tested the resulting mutant flies to see which ones failed to flee from areas of excessive heat. 600 possible candidate genes passed the first round of experiments. Eventually, the team narrowed their focus to a single gene called alpha2delta3, which encodes part of a calcium channel. Calcium and other ion channels are critical for nerve signal conduction, so it’s not surprising that they form an integral part of pain sensation.

The scientists next examined mice that were missing the same alpha2delta3 gene and found that they too lacked the heat avoidance behavior. MRI study of the mouse brains showed that rather than sending the pain signal to the cortex for processing, that signal was activating other senses, such as vision, smell or hearing. This sort of cross-activation of senses, also known as synesthesia, occasionally occurs in humans, though the connection to pain sensation has not previously been noted.

Finally, the molecular biologists examined 189 healthy human volunteers who had variations in or around their alpha2delta3 genes. Some of the mutations did result in reduced sensitivity to pain. Among another 169 patients who had undergone back surgery, the ones with these same mutations were much less likely to have persistent chronic pain.

The scientists hope that by identifying genes involved in sensing pain, doctors will be able to tailor analgesics to more closely fit patients’ needs.