Scratching itches when we offered some relief at first. It works because scratching causes mild pain neurons transmit the spine, instead of itch signals to the brain.
But then the brain releases a neurotransmitter called serotonin to deaden the pain and, according to a new study, the release of serotonin activates certain neurons in the spinal cord, causing more itching.
The researchers carried out their work in mice, but this vicious circle of itching and scratching may be what happens to us.
"The problem is that when the brain receives these signals pain, responsible for the production of serotonin to help control the pain."
says Zhou-Feng Chen, director of the University of Washington for the Study of itching, and adds:
"But as serotonin extends from the brain down the spine, passes from pain-sensitive neurons to influence the intensity of the itch."
In the study, the researchers genetically engineered mice that lacked the genes necessary to produce serotonin and then injected with a substance that causes itchy skin.
They found that these mice are not scratched much as normal mice. However, when these genetically modified mice were injected with serotonin, her reaction to itching again became normal.
This suggests that serotonin, which has a wide range of functions, but also important for itching sensation.
The findings may help find treatments for those experiencing chronic itch.
As a final conclusion, we can say that serotonin is released in response to pain scrape it does is cause more itching.