Serotonin plays key role in how we feel pain

Scientists have confirmed that the neurotransmitter serotonin plays a key role in pain management.
Researchers at Champalimaud Foundation in Lisbon have established the effect of serotonin on sensitivity to pain using a combination of advanced genetic and optical techniques.
"Serotonin is a small molecule known to be implicated in a wide range of brain functions, from the control of sleep and appetite, to the regulation of complex emotional behaviours," said Zachary Mainen, Champalimaud Neuroscience Programme director and principal investigator of the Systems Neuroscience Lab.
"This neurotransmitter is also popularly thought to contribute to feelings of well being and happiness, as some anti-depression medications work through increasing serotonin in the brain," Mainen said.

Serotonin's great importance led researchers to seek ways of understanding its function, but studying it has been a long-standing challenge.
"Most of the cells that produce serotonin are located in a defined cell group called the Dorsal Raphe Nucleus (DRN)," said Mainen.

"This cell group is small and located deep in the brain, which makes targeting it difficult.
"In addition, other cells that produce and release different molecules are also present in the DRN, which means that general stimulation of the area may result in the release of other molecules besides serotonin.
"To overcome the limitations of previous studies and explore the specific function of serotonin, we used a combination of light and genetics, an approach called optogenetics," said Guillaume Dugue, a former postdoctoral researcher in the lab of Mainen.

Using genetic techniques, the researchers expressed a light-sensitive protein specifically in the serotonin-producing cells of mice, so that when the researchers shone light on these cells, the cells released serotonin.
"The effect of the serotonin was clear. Mice that we stimulated to release serotonin showed a significant decrease in sensitivity to pain, when compared with mice in the control group," Dugue said.
The study was published in the journal PLoS One.