Scientists might have "scratched the surface" of the scratch-an-itch-then-it-itches-more mystery, according to Psychology Today.
The belief used to be that itching and pain followed the same nervous system road, but scientists now think itching signals have their own paths with itch-specific nerve cells and receptors. Pain can override the path for itching, which is why scratching - and the accompanying mild pain - can stop an itch, according to Psychology Today.
A new study published in Neuron relays how scientists at Washington University's Center for the Study of Itch have taken that idea even further. Senior author Zhou-Feng Chen and his team studied what took place once the pain signals caused by scratching hit the brain in mice.
The researchers found that when the brain gets the signal of pain, it produces serotonin. "But as serotonin moves from the brain into the spinal cord, the researchers found, it can 'jump the tracks,' moving from the pain pathway to the itching pathway," Psychology Today wrote. "When serotonin reacts with receptors on itch-sensing cells in the spinal cord, it can ratchet up the intensity of the itching."
The researchers then used mice engineered to lack serotonin-making genes. The mice were injected with an itch-provoking substance. The mice lacking the serotonin did not scratch as much as other mice in their litter that were injected with the same itch-making substance.
When the mice were given serotonin by injection, the genetically-altered mice scratched as would be expected from any other mouse.
This research could one day help those with chronic itching, but Chen said in a statement that blocking serotonin is not an option, according to Psychology Today. Serotonin fights pain, regulates mood, appetite and sleep. Chen suggested that blocking the communication between serotonin and nerves in the spinal cord might be the answer.
