Serotonin, we know, is a neurotransmitter responsible for mood balance, hence it being targeted in many antidepressant medications. But do serotonin levels have something to say about patience, too? A new study published in the journal Current Biology says yes.

A team of scientists from the Champalimaud Centre for the Unknown (CCU) in Portugal conducted an animal study in which mice had to wait for a reward to arrive at random times. During some of the trials, scientists stimulated serotonin neurons using a technique called optogenetics, which is a relatively new method used to control the brain with light. And when applied to neurons, the light activated and released serotonin into the brain, CCU team member Madalena Fonseca said in a press release.

After testing the different levels of activation on patience, the results showed the stronger activation, the longer mice were willing to wait for their reward. To make sure this wasn’t a result of a separate serotonin function, scientists also tested to see if stimulating these neurons alone was a reward for mice. The results, however, showed the opposite. So scientists have found a causal link between activation and release of serotonin.

This is on par with prior research published in the Frontiers in Behavioral Neuroscience that used optogenetics to understand the release of dopamine, another neurotransmitter, and its effect on addictive behavior. Dopamine helps control the brain’s reward and pleasure centers, and when activated to mimic tonic dopamine increases — low, but long-lasting levels — researchers found these spikes have a significant effect on drinking.

According to McGill University in Canada, both dopamine and serotonin are the chief operators of the accumbens nucleus, the part of the brain that plays a central role in the reward circuit. Given all this research, optogenetics could possibly be used to better understand the involvement of neurotransmitters in depression and other diseases, like addiction, Parkinson’s disease, and schizophrenia.

For now, neuroscientists are happy they're starting to understand the effects of neural activation and release on brain function.

"Because antidepressants are thought to increase serotonin, people assume that more serotonin neuron firing would feel good. Our results show that the story is not so simple," said Zachary Mainen, lead study author and director of the CCU neuroscience program. "That serotonin affects patience gives us an important clue that we hope will help us crack the serotonin mystery."

Source: Current Biology. 2014.