Researchers from the Washington University School of Medicine in St Louis found that scratching causes the brain to release serotonin, a neurotransmitter that makes the itching sensation more intense.

Although the study was conducted on mice, the same cycle of itching and scratching is thought to be the same in humans. Aside from proving the same mechanism occurs in humans, the research also provides new information that could aid in stopping the process. This could prove useful for individuals suffering from chronic itching.

Like Us on Facebook

Researchers have known for decades that scratching an itch produces a small amount of pain in the skin, said senior investigator Zhou-Feng Chen, PhD, director of Washington University's Center for the Study of Itch.

The pain can temporarily stop the itching by making neurons in the spinal cord relay the pain signals to the brain, as opposed to the itch signals.

"The problem is that when the brain gets those pain signals, it responds by producing the neurotransmitter serotonin to help control that pain," Chen explained.

"But as serotonin spreads from the brain into the spinal cord, we found the chemical can 'jump the tracks,' moving from pain-sensing neurons to nerve cells that influence itch intensity."

Although scientists discovered the role of serotonin in managing pain decades ago, the study is the first time the release of a chemical messenger from the brain has been associated with itching, Chen said.

Scientists bred a strain of mice without the genes required to produce serotonin. When the genetically modified mice were exposed to a substance that usually makes the skin itch, the mice didn't scratch the region as much as their normal littermates.

After injecting them with serotonin, however, the mice displayed the similar behavior of the normal mice and scratched in response to the itching compounds.

"So this fits very well with the idea that itch and pain signals are transmitted through different but related pathways," said Chen, a professor of anesthesiology, of psychiatry and of developmental biology. 

TagsSerotonin, Neurotransmitter, Genetically engineered mice, Genetic Engineering, Itch, Scratching, Excessive itching