A type of dopamine neuron not associated with the reward system is responsible for modulating movements in Parkinson’s disease. These results were reached by scientists from the Champalimaud Foundation, a Portuguese scientific organization specializing in biomedical research in the fields of neurology, oncology and cardiology. Research results published In the scientific journal Current Biology.
To further investigate the role of neurons in modulating movements, scientists conducted an experiment on laboratory mice. Scientists have developed a behavioral task for rodents that requires freely moving mice to press a lever with a paw to receive a reward (a drop of fresh water).
To understand what was happening in the mice’s brains during this task, the researchers used single-photon imaging. This method allows you to visualize the structure, function and biochemical properties of the brain. The observation focused specifically on the pars compacta of the brain’s substantia nigra. It is significantly affected in Parkinson’s disease.
Scientists tagged dopamine neurons in mice to light up when they were active. For this purpose, a special protein that glows under a microscope was used. This allowed the researchers to understand which neurons were activated during movement and reward.
It turns out that two types of dopamine neurons are “mixed” in the compact part of the brain’s substantia nigra. Some neurons were activated when the mouse was about to move, while others fired when the animal received a reward. Another important observation was that the firing of neurons depended on which paw the mouse used to press the button.
To find out how dopamine loss affects movement, researchers used a neurotoxin to selectively reduce the number of dopamine-producing cells on one side of the mouse brain to mimic Parkinson’s disease. As a result, the decrease in dopamine levels in one part of the brain led to less pressing of the paw on the levers on the other side of the body.
It is stated that in people with Parkinson’s disease, symptoms often occur asymmetrically, and the normal mobility of some parts of one side of the body is reduced.
The scientists stated that their discovery shows that dopamine neurons play a more complex role in the functioning of the human body; These neurons are not only associated with the reward mechanism. They hope the new research will lead to the development of new treatments tailored to the type of dopamine neurons lost.
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