Neurons paralyze motor function duringREM sleep13 December 2016

The glutamate neurons of the sublaterodorsal nucleusemit a spontaneous red fluorescence indicating that theviral vectors used have been successfully added. Credit:Sara Valencia Garcia / Patrice Fort, CNRS

During REM sleep, the brain inhibits the motorsystem, which makes the sleeper completelyimmobile. CNRS researchers working in the Centrede Recherche en Neurosciences de Lyon(CNRS/Université Claude Bernard Lyon1/INSERM/Université Jean Monnet) have identifieda population of neurons that is responsible for thistransient muscle paralysis. The animal modelcreated will shed light on the origin of someparadoxical sleep disorders, and more particularlythe condition that prevents this paralysis. It will alsobe most useful in the study of Parkinson's disease,

since these pathologies are related. This work waspublished on December 12, 2016 on the website ofthe journal Brain.

In spite of being in a deep sleep, the patients talk,move, kick and eventually fall out of bed. They aresuffering from a parasomnia called REM sleepbehavior disorder (RBD). This disorder usuallyappears around the age of 50. Muscles are at restduring the REM sleep phase, but in these patients,there is no paralysis, although the reason for this isnot known. The sleepers move abnormally,probably reflecting their dream activity.

A team from the Centre de Recherche enNeurosciences de Lyon (CNRS/INSERM/UniversitéClaude Bernard Lyon 1/Université Jean Monnet)has taken one more step towards elucidating thispathology. The researchers identified neurons inthe sublaterodorsal nucleus of the brain, ideallylocated to control motor system paralysis duringREM sleep. In rats, they specifically targeted thisneuron population, by adding genetically modifiedviral vectors to it. Once these are in the neuralcells, they block the expression of a gene thatallows synaptic glutamate secretion. Now incapableof releasing this excitatory neurotransmitter, theneurons can no longer communicate with theirneighbors. They are disconnected from the cerebralnetwork necessary for paralysis during REM sleep.

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In a normal rat specimen (A and B) the neurons of thesublaterodorsal nucleus (SLD, colored in brown) areglutamate neurons (also colored in black). In rats treatedwith viral vectors (C and D), neurons are still present.Credit: (in brown) but are not longer capable of releasingglutamate (absence of black color). Sara Valencia Garcia/ Patrice Fort, CNRS

For 50 years, the scientific community hasconsidered that these glutamate neurons generatedREM itself. This team's experience invalidates thishypothesis: despite the absence of activity in thisneuron circuit, the rats still experience this stage ofsleep. They are fast asleep and disconnected fromthe outside world, with eyes closed. But these ratsare no longer paralyzed. Their behavior is veryreminiscent of the clinical profile of patientssuffering from RBD. The glutamate neuronstargeted in this study play an essential part in REMparalysis during sleep and are reportedly the firstneurons affected in this neurological disease.

This research work goes beyond creating a newpreclinical model that mimics this parasomnia. Itmay be of paramount importance in studying someneurodegenerative diseases. Recent clinicalresearch has shown that patients diagnosed withRBD almost always develop the motor symptoms ofParkinson's disease, on average a decade later.The team is now attempting to develop an animalmodel that evolves from parasomnia intoParkinson's disease, in order to understand howneuron degeneration occurs.

More information: Genetic inactivation ofglutamate sublaterodorsal nucleus recapitulatesREM sleep Behavior Disorder. Sara ValenciaGarcia, Paul-Antoine Libourel, Michael Lazarus,Daniela Grassi, Pierre-Hervé Luppi and PatriceFort. Brain. Published online on December 12,2016. DOI: 10.1093/brain/aww310

Provided by CNRS

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APA citation: Neurons paralyze motor function during REM sleep (2016, December 13) retrieved 8September 2021 from https://medicalxpress.com/news/2016-12-neurons-paralyze-motor-function-rem.html

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