Neurotransmitters bind to a neuron. (Credit: Scientific Animations/CC BY-SA 4.0)Parkinson’s disease, a progressive disorder of the central nervous system, is estimated to affect more than 10 million people worldwide. Parkinson’s features include loss of mobility and involuntary movements such as tremors, making the disease inconvenient at best and debilitating at worst. For decades, it has been understood that Parkinson’s is caused by age-related brain degeneration that inhibits the production of dopamine. But dopamine—an important part of the brain’s movement and reward system—doesn’t work alone, and finding its neural foil has proven crucial to advancing scientists’ understanding of the disease as a whole.
Researchers in Oregon appear to have done just that. In a paper for the journal the nature, neuroscientists at Oregon Health and Science University (OHSU) describe the mechanism by which adenosine, another neurotransmitter, acts opposite to dopamine. Their findings have led to an improved understanding of how Parkinson’s begins to manifest in the brain.
A spinal cord motor neuron. (Photo: Berkshire Community College Bioscience Image Library/Wikimedia Commons)
Dopamine plays a key role in facilitating movement. It acts as a chemical messenger, allowing neurons to pass locomotive orders between the brain and other parts of the body. But if dopamine is the gas pedal, adenosine is the brake. While dopamine acts on a neuronal circuit that promotes movement, adenosine acts on a separate circuit that inhibits movement. Together, the two neurotransmitters use a “push-pull” system to orchestrate what we think of as normal, healthy movement.
The OHSU team confirmed adenosine’s role in locomotion in a study with mice. Using a genetic engineering technique they employed in previous studies, the researchers custom-developed protein probes, or single strands of DNA that probe their complementary sequences at a defined location. They then used two-photon fluorescence lifetime imaging to track adenosine activity in the rat brain.
Although there is still work to be done to fully understand the role of adenosine in Parkinson’s disease, the neuroscientists’ discovery points to a path that researchers can confidently investigate the behavior of the neurotransmitter. Drugs and other treatments targeting adenosine could provide a new way for medical experts to stop the onset of Parkinson’s or reduce symptoms for those already suffering from the disease.
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