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 eLifethey identified a new brain network, which connects pain to a specific region of the brain.
Burning, stabbing, tingling or even itching sensations would be reduced by deep stimulation of a subset of neurons located in the subthalamic nucleus, which also helps to reduce movement-related symptoms in the framework of the disease. The researchers wanted to explain the mechanisms.
“Dysfunction of pain processing pathways”
First, they used electrophysiology by measuring the triggering of electrical signals in nerve cells in the subthalamic nucleus of rats. After the latter had received a shock in the hind leg, the nerve cells appeared to be temporarily activated. Another observation, the response of the neurons was divided into three categories compared to the basic trigger 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 nuclei, signs of discomfort took longer to appear than healthy rats. In the case of Parkinson’s disease, the onset speed was higher and the responses to pain were greater. “All of these results suggest that the pain associated with Parkinson’s disease is due to a dysfunction of the pain processing pathways in the subthalamic nucleus”, can we read in the Inserm press release.
Towards more targeted pain treatment
The researchers were particularly interested in two cerebral structures known for their importance 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 decisive role they play in transmitting pain information to the subthalamic nucleus. They discovered that there is a direct communication pathway between the parabrachial nucleus and the subthalamic nucleus.
“The results we obtained show that the subthalamic nucleus is functionally linked to a pain processing 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 pain caused by Parkinson’s disease and other neurological diseases, by directing stimulation to specific parts of the brain.
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