Editor’s comment: Antidepressant medications have been found to help reduce some types of pain and are, therefore, often prescribed for fibromyalgia patients. However, until now, little has been known about exactly how or why they work. Scientists at the Champalimaud Neuroscience Programme have uncovered a mechanism that might explain one reason antidepressants have been effective for pain. Antidepressants increase the availability of serotonin. Serotonin, a neurotransmitter found in the brain and gastrointestinal tract, is typically low in FM patients. In the following press release, the researchers describe their discovery of how serotonin works to reduce pain.
Note: You may read the full text of this study free HERE.
In a study published in the scientific journal PLoS One, researchers at the Champalimaud Neuroscience Programme establish the effect of serotonin on sensitivity to pain.
“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, 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.” says Zachary Mainen, CNP director and principal investigator of the Systems Neuroscience Lab.
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),” explains 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,” says Guillaume Dugué, a former postdoctoral researcher in the lab of Zachary 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,” says Dugué. “Mice that we stimulated to release serotonin showed a significant decrease in sensitivity to pain, when compared with mice in the control group.”
“We devoted substantial efforts to optimising light activation of serotonin-producing cells. Overall these results provide a new level of evidence on the importance of serotonin in gating the influence of sensory inputs to behavioural outputs, a key physiological role that will help define large-scale theories of serotonin function. Moreover, it has possible implications for better understanding chronic pain treatment.” concludes Mainen.
Source: Press Release: Champalimaud Neuroscience Programme, August 28, 2014.