Parkinson’s disease is often associated with unexplained pain. Researchers from Inserm and the University of Grenoble Alpes have sought to understand this phenomenon. In a study published in the journal eLife, they identified a new brain network, which links pain to a specific region of the brain.
The sensations of burning, stabbing, tingling or even itching would be reduced by deep stimulation of a subset of neurons located in the subthalamic nucleus, which also helps reduce symptoms related to movements in the framework of the disease. The researchers wanted to explain the mechanisms.
“Dysfunction of the Pain Treatment Pathways”
First, they used electrophysiology by measuring the triggering of electrical signals in nerve cells in the subthalamic nucleus of rats. After the latter received a shock in the hind paw, the nerve cells appeared to be temporarily activated. Another finding, the response of neurons was divided into three categories with respect to the base triggering speed: an increase, a decrease or a maintenance of the speed.
Next, the team investigated whether the responses caused a change in brain function. For rats with damaged subthalamic nucleus, signs of discomfort took longer to appear than healthy rats. In Parkinson’s disease, the onset speed was faster and pain responses were greater. “All of these results suggest that the pain associated with Parkinson’s disease may be due to a dysfunction of the pain treatment pathways in the subthalamic nucleus”, we can read in the Inserm press release.
Towards more targeted pain treatment
The researchers were particularly interested in two brain structures known to be important in the transmission of injury signals from the spinal cord: the superior colliculus and the parabrachial nucleus. They blocked their activity, which allowed them to observe the determining role they play in transmitting information from pain to the subthalamic nucleus. They discovered that there is a direct line of communication between the parabrachial nucleus and the subthalamic nucleus.
“The results we obtained show that the subthalamic nucleus is functionally linked to a pain treatment network and that these responses are affected in parkinsonian syndrome,” concludes Véronique Coizet, Inserm researcher and director of the study in the press release.
The researchers wish to confirm their results through other studies, in order to characterize the effects of this deep brain stimulation. The goal is to develop a treatment for the pain caused by Parkinson’s disease and other neurological diseases, by directing the stimulation to specific parts of the brain.
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