Breakthrough in Parkinson's research reshapes understanding of dopamine's role

This discovery challenges long standing views of dopamine’s role in neurological disorders like Parkinson’s disease, a condition that affects more than 110,000 Canadians and millions worldwide. Parkinson’s develops when dopamine producing neurons in the brain gradually die, leading to symptoms such as tremors, slowed motion, and stiffness. Treatments like levodopa, which boosts dopamine levels, often restore mobility—but scientists have never fully understood why it works so effectively.

To answer that question, a team led by Dr. Nicolas Tritsch, assistant professor in McGill’s Department of Psychiatry and researcher at the Douglas Research Centre, turned to advanced mouse studies. Using optogenetics, a technique that uses light to control specific brain cells, the researchers monitored motor behavior while precisely turning dopamine neurons “on” or “off.” Mice were trained to press a weighted lever—a task requiring both speed and strength—while their brain activity was recorded in real time.

If brief dopamine bursts truly controlled movement intensity, changing dopamine levels mid task should have altered how hard or fast the animals pushed. Yet no such changes occurred. Instead, the researchers found that boosting dopamine beforehand helped the mice initiate movement but did not affect how forcefully they moved once they began. Conversely, restoring dopamine with levodopa improved overall ability to move, not moment by moment motion control.

The findings could reshape how Parkinson’s therapies are designed. Instead of targeting quick dopamine spikes, future treatments may focus on maintaining stable baseline dopamine levels—a simpler and potentially safer approach. By reframing dopamine as an essential enabler, rather than a micromanager, neuroscientists hope to refine treatment strategies that help patients reclaim motion and independence.

REFERENCE: Haixin Liu, Riccardo Melani, Marta Maltese, James Taniguchi, Akhila Sankaramanchi, Ruoheng Zeng, Jenna R. Martin, Nicolas X. Tritsch. Subsecond dopamine fluctuations do not specify the vigor of ongoing actions. Nature Neuroscience, 2025; 28 (12): 2432 DOI: 10.1038/s41593-025-02102-1