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A new study published in the Journal of Nature looked at how dopamine dynamics are dispensable for movement but promote reward responses.

“We tested whether rapid dopamine dynamics are necessary for the behavioral functions of dopamine,” study author Pascal S. Kaeser told us. “There is conflicting literature on each dopamine function as to whether it is mediated by fast and precise signaling or by slower, tonic signalling.” 

The research chose to do this study because of the fundamental importance of dopamine in regulating striatal circuits and behavior, and because of the importance of dopamine in diseases like Parkinson’s and addiction. 

A degeneration of nerve cells that control movement in the brain is to blame for the development of Parkinson's disease which is a progressive disorder. Once the nerve cells die or become compromised, the brain can no longer produce dopamine. A type of neurotransmitter and hormone, dopamine is responsible for our feelings of rewards and pleasure and not enough can cause the development of Parkinson's disease.

To test their theory, they built on previous work in which they generated mice that specifically lack rapid dopamine release. 

“We showed that the loss of rapid dopamine release in vitro leads to a loss of rapid dopamine dynamics in awake behaving mice,” Kaeser told us. “We showed that these dynamics are dispensable for movement initiation.”

The study also showed that the dynamics are likely important for behaviors related to motivation and learning because these behaviors are impaired in the mice. 

“We also showed that L-DOPA, a commonly used Parkinson’s disease drug, enhances movement without restoring dopamine dynamics,” Kaeser told us. “This helps explain the mechanism of action of L-DOPA and supports our overall conclusions.” 

The results suggest that a spontaneous form of dopamine release is really important for movement. It is important to define this form of signalling and to directly test its behavioral roles.

“The results suggest that motivation and/or learning are impaired when rapid dopamine dynamics are disrupted,” Kaeser told us. “It will be important to better understand why and how.”