By: Mallory Bachmann
UF researchers uncover a paradox in the brain that may open the door to earlier treatment.
A Tale of Two Neuron Types
In the human brain, two neighboring regions are packed with dopamine-producing neurons. One, called the substantia nigra (SNc), plays a key role in controlling movement and is also the primary site of dopamine neuron loss in Parkinson’s disease. Right next door is the ventral tegmental area (VTA). It looks similar under a microscope, but its neurons are far more resilient, surviving much longer as the disease progresses.
But what makes one group of neurons so vulnerable while the other seems to resist? That question prompted researchers at the Norman Fixel Institute for Neurological Diseases to take a closer look.
Catching Parkinson’s in Action
In a recent study, Dr. Habibeh Khoshbouei, professor of neuroscience at the University of Florida’s Fixel Institute and Department of Neuroscience, set out to discover what happens to these cells before they die. Khoshbouei and her team specifically looked at a protein called alpha-synuclein to see how it affects brain cell activity in mice.
Instead of waiting until the cells were gone, they captured an earlier stage: when the cells were still alive but “struggling.” In the SNc, neurons began firing abnormally fast and lost their ability to recover after stress. Meanwhile, neurons in the VTA stayed stable, showing little change.
By observing this process in real time, the team uncovered a hidden stage of Parkinson’s, a moment when cells are sick but not yet dead.
The Window of Opportunity
Researchers realized that this early stage could be the best chance for intervention, restoring normal brain activity before permanent damage sets in.
Parkinson’s symptoms like tremor, stiffness, and slowed movement do not appear until a large portion of dopamine-producing cells in the SNc have already died. By then, much of the damage is irreversible.
“When you lose a neuron in Parkinson’s or any neurological disorder, it’s irreversible,” explained Khoshbouei, “That’s why we always want to prevent the loss, delay it, or reduce the rate of it.”
What this study highlights is that there is a critical “sweet spot” before that point, when neurons are malfunctioning but still alive. In the SNc, they were firing too quickly and struggling to bounce back after stress, signaling that they were under pressure but not yet lost.
“The surprising part was that instead of seeing cell death after three or four weeks, we saw SNc neurons getting sick first,” Khoshbouei said. “Even more surprising was that neighboring VTA neurons seemed completely unaffected. That was unexpected, but also very exciting.”
If doctors can intervene during this stage, calming the overactive cells, restoring balance to their firing patterns, and stabilizing their energy use, it could mean slowing or even preventing the chain reaction that leads to Parkinson’s symptoms.
“In order to find effective treatments, we have to understand the timeline and progression of the disease. This early stage gives us the opportunity to study the problem before cell death happens, and that’s the window that could lead to truly effective therapies.”
What’s Next
Identifying this hidden stage is only the beginning. Leah Phan, the study’s first author and a senior graduate student in the Khoshbouei Lab, is now working to determine exactly when neurons tip from being “sick” to being permanently lost. By tracking the disease over a longer timeline, the team hopes to pinpoint the critical window when intervention offers the greatest chance of success.
The team will also test existing FDA-approved drugs, such as D2 receptor agonists. These medications mimic dopamine’s effects, helping dopamine neurons restore normal firing activity while sending dopamine-like signals to other neurons in the early stages of Parkinson’s disease. The goal is to determine whether these drugs can do more than ease symptoms, could they actually protect vulnerable neurons and re-establish healthy firing patterns before cell death occurs? If so, it could fast-track new treatments, since these medications are already available to patients.
Check out the full study here: Parkinson’s paradox: alpha-synuclein’s selective strike on SNc dopamine neurons over VTA | npj Parkinson’s Disease