Scientists have discovered why green color relieves pain

Exposure to green is known to help reduce pain levels, in particular, there is evidence that this color can alleviate pain in patients with arthritis, migraine and fibromyalgia. However, the reasons for this effect remained a mystery, writes naked-science portal.

Scientists from Fudan University and other scientific organizations in China conducted research on this issue and published the results in the journal Science Translational Medicine. The study was conducted on mice. To learn more about how light affects the brain, the team studied every part of the rodent visual nervous system, from the eyes to the gray matter.

They started with rod and cone photoreceptors on the outer retina of the eye. By shutting off each of these receptors at different times and testing what changes in pain sensation this leads to, the scientists found that the neural pathway to this effect starts with the rods and cones.

The team then examined the role of ganglion cells in the inner part of the retina, which receive signals from photoreceptors. Using genetic suppression, the authors of the work learned which of the cells are responsible for communication with the so-called ventral lateral nucleus in the thalamus, whose function is to help coordinate and plan movements.

After that, the scientists tracked the transmission of signals, sent light of different colors into the eyes of mice. It turned out that green light led to more intense signaling of gamma-aminobutyric acid, the most important inhibitory neurotransmitter of the central nervous system. This, in turn, increased the expression of the so-called Penk gene, which encodes a protein with a similar name, PENK. This protein is the precursor to a molecule called ENK, which activates opioid receptors in the brain, resulting in pain relief.