Brain Chemical Serotonin Neurons Help Humans to Be More Patient

A recent study of researchers shows that the brain chemical, serotonin, that is widely targeted to treat depression also helps humans have patience in life.

Serotonin is a neuromodulatory chemical that is targeted by antidepressant drugs, such as Prozac, which are widely used to treat depression and other disorders such aschronic pain.

“We made serotonin neurons sensitive to light so when we illuminated them, they were activated and released serotonin in the brain,” said Madalena Fonseca, member from the team of lead researcher Zachary Mainen at the Champalimaud Centre for the Unknown (CCU) in Lisbon, Portugal.

The scientists observed that when they activated serotonin neurons, mice became more patient. “The more serotonin neurons were activated, the longer the mice would wait,” added Masayoshi Murakami, another member of the CCU team.

Scientists also performed experiments to test if stimulation of serotonin neurons could act as a reward. “If the sensation of serotonin was pleasant or rewarding for the mice, this could have explained why they waited longer”, Fonseca noted.

To investigate the role of serotonin in patience, the researchers used a task in which mice have to wait for a reward that arrives at random times. During some of the trials, they stimulated serotonin neurons using a technique called optogenetics.

While testing whether mice preferred to perform actions associated with serotonin stimulation, it showed the result as negative, ruling out that increased patience was a consequence of reward.

The study has implications for understanding the involvement of serotonin in depression and other diseases. While antidepressants are thought to increase serotonin, people assume that more serotonin neuron firing would feel good.

While concluding, Mainen said, “Our results show that the story is not so simple. That serotonin affects patience gives us an important clue that we hope will help us crack the serotonin mystery.” The paper was appeared in the journal Current Biology.


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