How does a small cluster of similar cells in the brain that regulate breathing, appetite, and other functions?
The answer is that they are not as homogeneous. In recent years, scientists, including geneticist Susan Dimech from Harvard Medical School have identified different subtypes of serotonin neurons. Experts have identified two groups of neurons that help suppress aggression in male mice.
Opening to better understand the complex neural circuitry underlying aggression. "Serotonin neurons are sensitive to dopamine," - says Dimech, senior author of the study.
"There is evidence of interaction between serotonin and dopamine - she adds. - But now we have tied them to a certain group of cells. "
The authors suggest that dopamine accentuates aggression twice: on their own, as has been shown in earlier studies, but also due to the suppression of serotonin neurons that inhibit aggression.
Although the study was conducted only in mice, Dimech believes that surveillance will be similar in the case of man, partly because the corresponding area of the hindbrain is the same in all mammals.
If the information is confirmed in humans, the results will lead to more accurate treatment of excessive aggression, which occurs, for example, schizophrenia.
Serotonin affects aggressive behavior in humans and animals. Recent studies have linked low levels of serotonin with a high probability of pathological aggression. Doctors sometimes prescribed serotonin reuptake inhibitors to increase its level in patients suffering from aggression. Attempting to adjust the behavior of one can affect breathing, mood, libido and appetite.
Dimech realized that if she could find out which neurons affect the aggression, could be developed procedures to reduce the undesirable side effects. A team of scientists began experimenting with blocking neurotransmitter release in laboratory mice group. As might be expected, according to become more aggressive and began biting compared with intact rodent systems serotonin, experimental mice.
As a result of research Dimech and other scientists have discovered two neurons: Drd1a / Pet1.
Dopamine: an unexpected effect
Mice in which one of these neurons was silenced, were more aggressive. The suppression of other subtypes of serotonin neurons had no effect.
The researchers found that most of the cells of serotonin, close to the DRD2 / Pet1, respond to dopamine in another way, increasing their activity. Dimech team did not detect dopamine receptors on the surface, with the result that it remains a mystery what the cells are doing and how dopamine acts on them. Further experiments showed that dopamine receptor DRD2 / Pet1 activated in adolescence.
Both subtypes of serotonin neurons differ from their counterparts in the most unexpected way. It is not yet clear why the mouse brain contains several types of serotonin neurons, each of which is active at different stages of development. It remains to be seen scientists.