By Chuck Seegert, Ph.D.
By optically stimulating the anterior cingulate cortex in mice, researchers at the University of Texas at Arlington (UT Arlington) were recently able to dampen the animals’ sense of pain. The new method specifically targets the inhibitory neurons in the brain, decreasing pain associated neuronal activity and pain-associated behavior, an advance that could lead to new strategies for managing chronic pain.
A significant body of evidence implicates the anterior cingulate cortex (ACC) in the perception of pain, which makes it a likely target for pain control studies. Historically, attempts to stimulate this region using electrodes have met with limited success, because the excitatory neurons are stimulated along with the inhibitory neurons. Scientists believe that specific stimulation of the inhibitory neurons of the ACC could reduce the perception of pain.
Using optogenetics, a team from the University of Texas at Arlington now appears to have found a way to specifically stimulate the inhibitory neurons of the ACC, according to a recent press release from the university. By stimulating this small region of the brain with certain wavelengths of light, the researchers significantly reduced response to mechanical pain stimulation — like pin pricks — in mice. Additionally, injecting small amounts of chemicals under the skin, another pain stimulation method, generated a much smaller pain response thanks to the optogenetic treatment.
While pain is a sensation that most people don’t enjoy, it does play an important role in how we interact with our environment.
“While reducing the sensation for chronic pain by optical stimulation, we still want to sense certain types of pain because they tell us to move our hands or legs away from something that is too hot or that might otherwise hurt us if we get too close,” Samarendra Mohanty, an assistant professor of physics at UT Arlington, said in the press release.
The mice that were studied had been genetically modified to express channelrhodopsin-2 in the inhibitory neurons of the ACC, according to a recent study published by the team in PLOS One. By stimulating these neurons, the researchers were able to confirm a decreased electrophysiologic response by the neurons in the ACC. This inhibition could also be modulated based on the intensity of the light used to optogenetically stimulate the tissue, as well as its frequency. The results obtained by the new approach led the team to conclude that it may have potential as a clinical alternative to chronic pain inhibition.
Optogenetics is an area of research that is rapidly gaining momentum in the medical space. Researchers at the University of California, Irvine, are exploring use of the method to treat temporal lobe epilepsy.