Genetic inactivation of glutamate neurons in the rat sublaterodorsal tegmental nucleus recapitulates REM sleep behaviour disorder

Abstract

SEE SCHENCK AND MAHOWALD DOI101093/AWW329 FOR A SCIENTIFIC COMMENTARY ON THIS ARTICLE: Idiopathic REM sleep behaviour disorder is characterized by the enactment of violent dreams during paradoxical (REM) sleep in the absence of normal muscle atonia. Accumulating clinical and experimental data suggest that REM sleep behaviour disorder might be due to the neurodegeneration of glutamate neurons involved in paradoxical sleep and located within the pontine sublaterodorsal tegmental nucleus. The purpose of the present work was thus to functionally determine first, the role of glutamate sublaterodorsal tegmental nucleus neurons in paradoxical sleep and second, whether their genetic inactivation is sufficient for recapitulating REM sleep behaviour disorder in rats. For this goal, we first injected two retrograde tracers in the intralaminar thalamus and ventral medulla to disentangle neuronal circuits in which sublaterodorsal tegmental nucleus is involved; second we infused bilaterally in sublaterodorsal tegmental nucleus adeno-associated viruses carrying short hairpin RNAs targeting Slc17a6 mRNA [which encodes vesicular glutamate transporter 2 (vGluT2)] to chronically impair glutamate synaptic transmission in sublaterodorsal tegmental nucleus neurons. At the neuroanatomical level, sublaterodorsal tegmental nucleus neurons specifically activated during paradoxical sleep hypersomnia send descending efferents to glycine/GABA neurons within the ventral medulla, but not ascending projections to the intralaminar thalamus. These data suggest a crucial role of sublaterodorsal tegmental nucleus neurons rather in muscle atonia than in paradoxical sleep generation. In line with this hypothesis, 30 days after adeno-associated virus injections into sublaterodorsal tegmental nucleus rats display a decrease of 30% of paradoxical sleep daily quantities, and a significant increase of muscle tone during paradoxical sleep concomitant to a tremendous increase of abnormal motor dream-enacting behaviours. These animals display symptoms and behaviours during paradoxical sleep that closely mimic human REM sleep behaviour disorder. Altogether, our data demonstrate that glutamate sublaterodorsal tegmental nucleus neurons generate muscle atonia during paradoxical sleep likely through descending projections to glycine/GABA premotor neurons in the ventral medulla. Although playing a role in paradoxical sleep regulation, they are, however, not necessary for inducing the state itself. The present work further validates a potent new preclinical REM sleep behaviour disorder model that opens avenues for studying and treating this disabling sleep disorder, and advances potential regions implicated in prodromal stages of synucleinopathies such as Parkinson's disease.

Neuroscience: A Distributed Neural Network Controls REM Sleep

“…Jouvet specifically found that lesions of this region in cats caused a perculiar state dissociation in which the animals appeared to ‘act out’ their dreams. Subsequent experimental work spanning several decades further refined the location of this ‘atonia generator’ to a region of the pons called the sublaterodorsal nucleus (SLD) in rodents (also termed the subcoeruleus region) [8,14,84–86] (Figure 3). …”

“…Selective disruption of glutamatergic transmission of SLD and dorsally adjacent caudal laterodorsal tegmental (cLDT) neurons produces REM sleep without atonia. Interestingly, inactivation of these same neurons also reduced total time spent in REM sleep in mice [86,90]. Hence in addition to regulating REM sleep motor atonia, glutamatergic cLDT-SLD neurons also play a role in generating the forebrain features of REM sleep.…”

“…For example, chemical, electrolytic and neuron-specific lesions of the REM sleep circuit, including the SLD and vM, result in loss of normal REM sleep paralysis and RBD-like motor behaviours in cats and rodents [8,14,84–86] (Figure 3). In addition, tumours or strokes that cause lesions of the dorsal pons where REM sleep circuits are located also cause RBD-like behaviours in humans [136,137].…”

Sleep‐related motor and behavioral disorders: Recent advances and new entities

“…) . In a recent study, a research group from Lyon demonstrated that genetic inactivation of glutamate neurons in the rat pontine sublaterodorsal tegmental nucleus was sufficient to cause loss of REM atonia . These findings mirror a human study using neuromelanin‐sensitive magnetic resonance imaging, in which reduced signal intensity in an equivalent region (the locus coeruleus/subcoeruleus complex) was observed in idiopathic RBD patients …”

Animal Model for Prodromal Parkinson’s Disease

“…In autopsy brains of PD patients who developed PD and dementia with Lewy bodies (DLB) preceded by idiopathic RBD, LBs were identified in the pedunculopontine tegmental nucleus (PPN), locus coeruleus/subcoeruleus complex, and gigantocellular reticular nucleus in medulla oblongata [46]. These regions are considered part of the neural circuit controlling atonia during REM sleep in animal experiments [6,47,48] and thus responsible for RBD. In this way the pathological progression of PD largely follows Braak's staging.…”