Optogenetics is a field I've only just discovered, but a cursory search of i09 suggests I'm very late to this particular party. No matter, writing here on whitenoise has been really great for forcing me to look into areas of research outside my own. This week, I ventured into the journal 'Nature Biotechnology' for the first time and came across this paper.

Optogenetics, for those of you who have been hiding under the same rock as me, is the stimulation and monitoring of neurons using optical techniques. It's the sort of research that leads to spectacular headlines like "Scientists use light to control monkey brains" or "Scientists Demonstrate Laser-Powered Mind Control in Best Way Possible" or mine above. (Writing online has also taught me the term "click bait" and now there's no turning back.) Lately, the big innovation in optogenetics has been efforts to stimulate neurons outside the brain.

In this study, they're focusing on the modulation of afferent nociceptors, the neurons that send pain signals to the brain, in mice . This sort of thing has been tried before, but only using mice which had been genetically modified to produce light-sensitive compounds. While interesting, using special mice limits the potential cross-species applications of the technique. We are certainly not at the point of genetically modifying humans to be light responsive. That's where this new study is more interesting. Instead of modifying the mouse genome, they actually injected regular mice with a virus that had been engineering to express a light-sensitive protein.

After two to four weeks, tests showed that the light-sensitive protein was indeed active within the mice. The researchers then shone blue light on their tiny mouse paws and observed clear indications of mouse pain (squealing, licking, flinching). Poor little guys. So evidently this particular procedure does the opposite of what we might hope. But it's valuable anyway for a number of reasons.

  • First, they were able to stimulate neurons with light on a part of the body that is not the brain and not transparent (like the corneas, for example).
  • Second, they were the first to do this targeting afferent nociceptors.
  • Third, they were able to do it without genetically modified mice, meaning the procedure could actually be adapted for humans in the (very) distant future.
  • Fourth, in the meantime, its a noninvasive way to study peripheral neurons and the affect of pain medications.

That's a pretty substantial bit of progress I'd say. Though perhaps not if you're a mouse.


Read the original paper, Virally mediated optogenetic excitation and inhibition of pain in freely moving nontransgenic mice, here.
The background in the top image is from Brevia, but the skill with which the clip art mouse has been overlaid is all me.