Science︱ Mouse REM sleep is regulated by dopamine signaling in the basolateral amygdala

Written by ︱ Yuanjia Zheng edited ︱ Sizhen Wang Sleep-wake state is affected by noradrenergic neurons, histaminergic neurons, and serotonergic neurons, which are located in the nucleus locus coeruleus, the ventral dorsal inner tubercle mammary nucleus of the thalamus, and the raphe dorsal nucleus
.

These neurons fire rapidly during wakefulness, slowly and occasionally during non-rapid eye movement (NREM) sleep, and almost stop firing during rapid eye movement (REM) sleep [1-2]
.

Dopaminergic neurons (DAVTA neurons) of the ventral tegmental area (VTA) have distinct firing patterns from other monoaminergic neurons [3-4], and they exhibit lower rates during NREM sleep than during wakefulness or REM sleep , which begins to increase before the transition between NREM-REM and NREM-awake transitions [5]
.

DAVTA neurons consist of heterogeneous populations with different input and output organizations [6-7], suggesting that there may be multiple populations of DAVTA neurons with distinct firing patterns during sleep-wake states
.

 On March 4, 2022, Emi Hasegawa (first author), Takeshi Sakurai (corresponding author) and others from the International Institute of Integrative Sleep Medicine (WPI-IIIS), University of Tsukuba, Japan, published a paper entitled "Rapid eye movement sleep" in Science.
is initiated by basolateral amygdala dopamine signaling in mice”
.

The authors examined extracellular dopamine (DA) levels throughout the sleep-wake cycle in several brain regions densely projected by DAVTA neurons, using DA sensors to determine the presence of subpopulations of DAVTA neurons and their role in sleep-wake regulation different effects
.

 The authors first expressed GRABDA (a G protein-coupled receptor for DA activated by G protein-coupled receptors) in the basolateral amygdala (BLA), nucleus accumbens (NAc), medial prefrontal cortex (mPFC), and lateral hypothalamus (LHA) of mice.
sensors) and implanted optical fibers for detection to study the relationship between DA levels and each sleep-wake state transition
.

It was found that there are three dynamic modes of DA during the transition from NREM to REM
.

The first: in BLA, DA levels briefly increase before each NREM-to-REM transition and decrease during REM sleep (Fig.
1 AD)
.

Second: DA levels in the NAc were also shown to be elevated before the transition from NREM to REM sleep, fluctuated during REM sleep with slightly higher mean values ​​(Fig.
1 EH)
.

Third: DA levels had similar temporal patterns in the mPFC and LHA, with a marked decrease in DA levels during REM sleep, which did not increase before (Fig.
1 IP)
.

Figure 1 Temporal changes of DA levels in various brain regions under different alert states (Source: Emi Hasegawar, et al.
, Science, 2022) Next, the authors investigated the effect of the increase in DA in BLA and NAc during NREM sleep on the sleep-wake state influence
.

The authors expressed stabilized step function opsin (SSFO) [8] in DAVTA neurons of DAT-ires-Cre mice (Fig.
2A, H), and implanted them bilaterally in BLA or NAc.
Into the optical fiber for optogenetic stimulation (1s)
.

During NREM sleep, DA fibers activating the BLA induced a transition to REM sleep, which began at 142.
4 ± 33.
7 s after stimulation, significantly earlier than that observed in controls (Fig.
2 BC)
.

BLA DA photostimulation every 30 min increased REM sleep, and the electroencephalogram (EEG) in each state did not change significantly as a result of photostimulation of DA neurons in the BLA (Fig.
2DF)
.

NREM sleep duration was shortened by premature termination of optogenetic stimulation
.

In contrast, excitation of DA fibers in the NAc did not induce state transitions during NREM sleep (Fig.
2 GJ)
.

Stimulation every 30 minutes (1 s) resulted in a slight increase in NREM sleep time and a decrease in wake time (Fig.
2 KL), consistent with previous studies showing that excitation of direct pathway neurons in the NAc reduces wakefulness [9], But this operation does not affect REM sleep
.

Exciting DA fibers of the mPFC or LHA also did not affect the number of each state
.

These results suggest that an acute increase in DA in the BLA causes a sleep transition from NREM to REM
.

Consistently, inhibition of DAVTA in the BLA prolonged REM sleep latency and reduced REM sleep volume without affecting EEG
.

Figure 2 During non-REM sleep, optogenetic excitation of DAVTA fibers in the BLA can induce REM sleep (Source: Emi Hasegawar, et al.
, Science, 2022) Studies have shown that complete depletion of DA in mice can eliminate REM sleep, The application of dopamine receptor D2 (Drd2) agonists can restore [10], and another study showed that low doses of Drd2 agonists increased REM sleep, while high doses of Drd2 agonists reduced REM sleep [11]
.

These findings suggest that Drd2 is involved in the regulation of REM sleep
.

Combined with the results in Figure 1, the authors hypothesized that DA acts on Drd2-positive neurons in the BLA to initiate REM sleep
.

To test this hypothesis, first, the authors performed whole-cell recordings of BLA Drd2-positive neurons after expressing SSFO in DAVTA neurons of Drd2-Cre;DAT-ires-Cre mice and found that DA fibers were stimulated with light (1 s) induced persistent hyperpolarization that could be blocked by Drd2 antagonists (Fig.
3 AD), suggesting that DA inhibits Drd2 neurons in the BLA via Drd2
.

Next, the authors expressed vLWO (a low-wavelength protein that couples to G proteins and induces hyperpolarization by light) in Drd2 neurons in the BLA of Drd2-Cre mice, and whole-cell recordings showed that light pulses (462 nm, 1 Hz, 40 s) caused persistent hyperpolarization of enhanced yellow fluorescent protein (EYFP)-positive neurons, similar to the hyperpolarization observed when DA fibers were excited (Fig.
3EH), suggesting optogenetic inheritance of BLA Drd2-positive cells Inhibition induced REM sleep
.

Next, we demonstrated that optogenetic inhibition of Drd2 neurons following implantation of optical fibers in the BLA of vLWO-expressing Drd2-Cre mice induced a transition from NREM to REM sleep (Fig.
3 IJ)
.

REM sleep began at 89.
2 ± 20.
3 s after stimulation, significantly earlier than controls; a light pulse every 30 min increased REM sleep volume and decreased NREM sleep without affecting EEG spectra (Fig.
3 LN), but the duration of NREM sleep shortened (Fig.
3 KO), indicating that inhibition of Drd2 cells caused inhibition of BLA neurons
.

Additionally, chemogenetic inhibition of Drd2 neurons in the BLA of Drd2-Cre mice increased REM sleep time and decreased NREM sleep time (Fig.
3QS), further supporting the importance of Drd2 neurons in the BLA in triggering REM sleep
.

At the same time, an increase in the number of Fos-positive neurons in the BLA as well as in the central amygdala (CeA) was observed (Fig.
3 PT), indicating that Drd2 neurons in the BLA are mainly active within the BLA
.

Therefore, these results above demonstrate that Drd2-positive neurons in the BLA mediate the transition from NREM to REM sleep
.

 Figure 3 Drd2-positive neurons in the BLA mediate the transition from NREM to REM (Source: Emi Hasegawar, et al.
, Science, 2022) Cataplexy is a pathological phenomenon in which REM sleep invades wakefulness
.

Previous studies have shown that Drd2 agonists or antagonists increase or decrease convulsions in sleepy dogs and mice, respectively [12-14]
.

So, is DA signaling in the BLA also involved in the appearance of convulsions? To this end, the authors expressed GRABDA in the BLA of narcolepsy mice (orexin-ataxin 3) [15], and implanted optical fibers to observe the relationship between DA levels and convulsions (Fig.
4A), while feeding the mice Chocolate to increase the number of seizure-like seizures [16]
.

Convulsion-like episodes (cataplexylike episodes, CLEs) are characterized by sudden onset of behavioral pauses [17]
.

First, the authors observed a transient increase in DA levels when eating chocolate, followed by CLEs; the increase in DA levels in the BLA of narcolepsy mice was greater during chocolate feeding than in controls (Figure 4BC)
.

Then, in DAT-ires-Cre mouse DAVTA neurons expressing SSFO, light stimulation for 1 s increased Fos expression in VTA SSFO-positive cells, causing a transient increase in DA levels (Fig.
4 DE), which is similar to the aforementioned lethargy Symptoms observed when mice were fed chocolate before convulsions
.

In Drd2-Cre mice expressing vLWO, BLA optogenetic inhibition (1 Hz, 1 min) induced CLEs in the awake state, and EEG profiles during induction of CLEs were similar to those observed during convulsions in narcolepsy mice (Fig.
4DH).
, while the number of Fos-positive neurons in the BLA increased after optogenetic inhibition (Fig.
4I)
.

Then, the authors injected AAV-DIO-hM4DimCherry into the BLA of Drd2-Cre;orexin-ataxin 3 mice to study the effect of chemogenetic inhibition of Drd2-positive neurons in the BLA on convulsions and found that CNO (clozapine-N -Oxide) treatment increased the total time and number of convulsive seizures and also increased the number of Fos-positive neurons in the BLA and CeA (Fig.
4 JM)
.

These results collectively suggest that transient elevation of DA levels in the BLA triggers convulsions, demonstrating that BLA DA signaling is also involved in the appearance of convulsions in mice
.

Figure 4.
The acute increase in DA levels in BLA triggers convulsions in narcolepsy mice (Image source: Emi Hasegawar, et al.
, Science, 2022) Conclusions and discussions, inspiration and prospects ) sleep and rapid eye movement (REM) sleep alternately, but the relevant mechanism of this sleep cycle has not been studied in depth
.

The amygdala plays a key role in processing emotional signals during wakefulness
.

Using techniques such as optical fiber recording and EEG recording, the present study found that an acute increase in dopamine (DA) levels in the basolateral amygdala (BLA) during NREM sleep terminates NREM sleep and initiates REM sleep, and that DA acts in the BLA by acting on it.
Neurons expressing the dopamine receptor D2 (Drd2) induce the transition from NREM to REM
.

This mechanism was also observed in narcolepsy mice, which temporarily increased DA levels in the BLA before convulsive onset, but not in wild-type mice (Fig.
4)
.

Positive emotions induce a transient increase in DA in the BLA of narcolepsy mice and trigger the NREM-REM transition and corresponding DA dynamics
.

These results suggest that DA signaling in the BLA plays a key role in initiating REM sleep, which provides a neuronal mechanism for understanding the generation of sleep cycles.
These findings also help to reveal the mechanism of convulsions and understand the pathophysiology of abnormal REM sleep.
Such as REM sleep behavior disorder and disorders involving abnormal DA signaling (eg Parkinson's disease)
.

Link to the original text: https:// Selected articles from previous issues [1] Nat Neurosci︱ Neuroimmunity and synapse-related pathways in the amygdala and anterior cingulate gyrus in patients with bipolar disorder Down-regulation 【2】Dev Cogn Neurosci︱Different comparison processes of functional near-infrared spectroscopy data of infants【3】Nat Commun︱Zhou Xiaoming/Sun Ziyi team revealed the molecular mechanism of the ligand entry pathway based on the open conformation of Sigma-1 receptors【4】 Glia︱Yuan Jianqiang's group reveals a new mechanism for regulating the proliferation of oligodendrocyte precursor cells: c-Abl phosphorylates Olig2[5] HBM︱Yu Lianchun's group reveals the relationship between the brain avalanche critical phenomenon and fluid intelligence and working memory[6] J Neuroinflammation︱Gu Xiaoping's research group reveals the important role of astrocyte network in long-term isoflurane anesthesia-mediated postoperative cognitive dysfunction【7】Nat Methods︱Fei Peng/Zhang Yuhui Research Group Co-Report Live New progress in cellular super-resolution imaging research【8】J Neurosci︱Qiang Zhou’s group reveals that extrasynaptic NMDARs bidirectionally regulate intrinsic excitability of inhibitory neurons 【9】JCI︱Jun Wang’s group reveals that long-term alcohol consumption leads to impaired cognitive flexibility The mechanism of damage [10] PNAS︱ Zhang Chunli's research group revealed that astrocyte regeneration has become a high-quality scientific research training course recommendation for multi-lineage neuronal cells [1] Scientific research skills︱ The 4th near-infrared brain function data analysis class (Online: 2022.
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18~4.
30) [2] Scientific Research Skills︱Introduction to Magnetic Resonance Brain Network Analysis (Online: 2022.
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2-3 Tencent Online) References (swipe up and down to view) [1]TE Scammell, E.
Arrigoni, JO Lipton, Neuron 93, 747–765(2017).
[2]CB Saper, TC Chou, TE Scammell, Trends Neurosci.
24, 726–731 (2001).
[3] L.
Dahan et al.
, Neuropsychopharmacology 32,1232–1241(2007).
[4]JM Monti, H.
Jantos, Prog.
Brain Res.
172, 625–646 (2008).
[5]A.
Eban-Rothschild, G.
Rothschild, WJ Giardino, JR Jones, L.
de Lecea, Nat.
Neurosci.
19, 1356–1366 (2016).
[6]KT Beier et al.
, Cell 162, 622–634 (2015).
[7]KT Beier et al.
, Cell Rep.
26 , 159–167.
e6 (2019).
[8]O.
Yizhar et al.
, Nature 477, 171–178 (2011).
[9]Y.
Oishi, M.
Lazarus, Neurosci.
Res.
118, 66–73 (2017).
[10]K.
Dzirasa et al.
, J.
Neurosci.
26, 10577–10589 (2006).
[11]JM Monti, D.
Monti, Sleep Med.
Rev.
11, 113–133 (2007) .
[12]CR Burgess, G.
Tse, L.
Gillis, JH Peever, Sleep 33, 1295–1304 (2010).
[13]S.
Nishino et al.
, J.
Neurosci.
11, 2666–2671 (1991) .
[14]E.
Mignot et al.
, J.
Neurosci.
13, 1057–1064 (1993).
[15]J.
Hara et al.
, Neuron 30, 345–354 (2001).
[16]Y.
Oishi et al.
, J.
Neurosci.
33, 9743–9751 (2013).
[17]TE Scammell, JT Willie, C.
Guilleminault, JM Siegel, International Working Group on Rodent Models of Narcolepsy, Sleep 32, 111–116 (2009).
Plate making︱Sizhen Wang End of this article