Researchers at the University of Copenhagen have identified a specific set of neurons in the brainstem that, when stimulated by electric pulses, can help improve the mobility of patients with Parkinson’s disease.
Without a known cure, treatment for Parkinson’s focuses on reducing the severity of symptoms. Since the disease is characterized by a deficit of dopamine in the brain, the most common treatment involves drugs that boost dopamine levels, but these become less effective as the disease progresses.
Since the 1990s, deep brain stimulation (DBS) has been used to treat Parkinson’s. This procedure involves implanting thin metal wires in the brain, which send small jolts of electricity to certain neurons. This works to alleviate symptoms like tremors and may even slow progression of the disease.
But one symptom that DBS has struggled to improve is what’s known as freezing of walking. During these episodes, people report that their feet feel like they’re glued to the floor momentarily, and the pause can often cause falls. Attempts to use DBS to improve this and other mobility issues have come up short, and that may be because scientists weren’t sure exactly which region of the brain they should be targeting.
For the new study, the Copenhagen researchers set out to find that optimal target. Previous studies have shown that a good place to start may be the pedunculopontine nucleus (PPN), a region of the brainstem that sends signals from the brain to initiate movements in the body.
In mouse models of Parkinson’s disease, the team systematically targeted different areas and cell types in the PPN. That helped them identify a group of excitatory neurons that were particularly promising.
“When we stimulated these specific neurons in the caudal area of the PPN, the animals were able to walk normally, across longer distances and with normal walking speed, as opposed to before the stimulation, where they would display symptoms of Parkinson’s disease,” said Debora Masini, first author of the study.
As intriguing as the study is, it’s important to remember that results in mice don’t always carry across to humans. In this case, the team also studied mice that had been engineered so that their neurons responded to pulses of light and chemical signals, which aren’t viable methods in humans. However, now that the optimal neurons have been identified, they could be targeted by DBS in humans.
The research was published in the journal Nature Communications.
Source University of Copenhagen
