The more serotonin in the brain has a mouse, the longer it can wait patiently for a reward. This result, written by Magdalene Fonseca, Masayoshi Murakami and Zachary Mainen, neuroscientists at the Champalimaud Foundation in Lisbon, was published on Thursday in the journal Current Biology .
Serotonin is one of the key chemicals that mediate the transmission of information in the brain nerve. It is produced by small groups of neurons located in the brainstem raphe nuclei called and is the target of the antidepressant Prozac family. These medications, also known by the acronym SSRI, act preventing the reuptake of serotonin by neurons, doing so increase extracellular serotonin levels in the brain. And to the extent that serotonin is associated with emotional states – in particular the sensation of wellbeing – it is thought that this increase is that alleviates depressive symptoms
However, what. serotonin does exactly is yet to unravel. “Serotonin is a mystery because it is involved in many things, but that even after the publication of more than 10,000 scientific articles (!), Neurosciences can not build a coherent and consensual theory of what she does,” said Zach PUBLIC Mainen. “Most people associate serotonin happiness because of SSRI, but neuroscientists do not see things that way.”
Mainen and his colleagues study the neural processes involved in decision making. And in particular, try to understand what makes someone give up (or not) to wait for a given event when it is slow to happen.
“It interests me realize where it comes from patience and see how a system brain can conflict with each other, or to compete or other control system, “explains Zach Mainen. “Freud spoke in terms of id versus ego and today we speak of executive functions, but it remains very unclear how this works at the level biological. So we are trying to address some major issues studied in great detail a very simple thing:. Postponing a decision “
In the study now published, the scientists analyzed the role of serotonin in patience through experiences with mice in which the animals had to wait for a reward that took an indefinite time to come. During these trials, the team could stimulate comfortable serotonin production by the animals’ brains thanks to said technique of “optogenetics”, increasingly used in such studies. “We have made the neurons that produce serotonin sensitive to light and so when the iluminávamos, they activavam up and freed serotonin,” says Magdalene Fonseca in a statement of the foundation.
The authors found so that when the activavam Serotonin-producing cells of the mice became more patients. “We tried with varying degrees of activation and found that, the greater the activation, the longer it [the animals] could wait,” added Masayoshi Murakami, quoted in the same document.
But the scientists showed yet another thing – something they say goes against the idea that antidepressants that act on serotonin function simply increasing the sense of well-being of depressed people. More specifically, made a further experiment to determine whether or not the mice preferred to perform tasks during which the production of serotonin by neurons was stimulated his. “If the feeling [produced by higher levels] serotonin was pleasant or rewarding,” says Magdalene Fonseca, “this could explain why the mice were willing to wait” when their serotonin neurons were stimulated producers than when were not.
The results contradict this hypothesis. “Our results show that the history [serotonin] is not that simple,” says Zach Mainen. “They question the existence of a motivational or emotional effect [serotonin] as usually think, before pointing to an effect on our perceptions and our actions” (which is what is at stake in experiences about patience) .
The study may allow better understanding of the role of serotonin in depression and other diseases, the authors conclude. “The fact that the antidepressant effect of SSRI take two to three weeks to manifest itself is a puzzle,” says Zach Mainen, “and suggests that this effect [on mood] is not the primary effect of serotonin increase.” For So Mainen think that the connection between the increase in serotonin and the antidepressant effect is indirect. “We do not know what that connection is, but we can speculate that the effects on the patience we see in our experiments are part of it. It’s a very complex issue … “
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