Monochromatic Blue Light Activates Suprachiasmatic Nucleus Neuronal Activity and Promotes Arousal in Mice Under Sevoflurane Anesthesia

High-Performance Bidirectional Microelectrode Array for Assessing Sevoflurane Anesthesia Effects and In Situ Electrical Stimulation in Deep Brain Regions

Precise assessment of wakefulness states during sevoflurane anesthesia and timely arousal are of paramount importance to refine the control of anesthesia. To tackle this issue, a bidirectional implantable microelectrode array (MEA) is designed with the capability to detect electrophysiological signal and perform in situ deep brain stimulation (DBS) within the dorsomedial hypothalamus (DMH) of mice. The MEA, modified with platinum nanoparticles/IrOx nanocomposites, exhibits exceptional characteristics, featuring low impedance, minimal phase delay, substantial charge storage capacity, high double-layer capacitance, and longer in vivo lifetime, thereby enhancing the sensitivity of spike firing detection and electrical stimulation (ES) effectiveness. Using this MEA, sevoflurane-inhibited neurons and sevoflurane-excited neurons, together with changes in the oscillation characteristics of the local field potential within the DMH, are revealed as indicative markers of arousal states. During the arousal period, varying-frequency ESs are applied to the DMH, eliciting distinct arousal effects. Through in situ detection and stimulation, the disparity between these outcomes can be attributed to the influence of DBS on different neurons. These advancements may further our understanding of neural circuits and their potential applications in clinical contexts.

Distinct Neural Mechanisms Between Anesthesia Induction and Emergence: A Narrative Review

Anesthesia induction and emergence are critical periods for perioperative safety in the clinic. Traditionally, the emergence from general anesthesia has been recognized as a simple inverse process of induction resulting from the elimination of general anesthetics from the central nervous system. However, accumulated evidence has indicated that anesthesia induction and emergence are not mirror-image processes because of the occurrence of hysteresis/neural inertia in both animals and humans. An increasing number of studies have highlighted the critical role of orexinergic neurons and their involved circuits in the selective regulation of emergence but not the induction of general anesthesia. Moreover, additional brain regions have also been implicated in distinct neural mechanisms for anesthesia induction and emergence, which extends the concept that anesthetic induction and emergence are not antiparallel processes. Here, we reviewed the current literature and summarized the evidence regarding the differential mechanism of neural modulation in anesthesia induction and emergence, which will facilitate the understanding of the underlying neural mechanism for emergence from general anesthesia.

TDP-43 deficiency in suprachiasmatic nucleus perturbs rhythmicity of neuroactivity in prefrontal cortex

Individuals within the amyotrophic lateral sclerosis and frontotemporal dementia disease spectrum (ALS/FTD) often experience disruptive mental behaviors and sleep-wake disturbances. The hallmark of ALS/FTD is the pathological involvement of TAR DNA-binding protein 43 (TDP-43). Understanding the role of TDP-43 in the circadian clock holds promise for addressing these behavioral abnormalities. In this study, we unveil TDP-43 as a pivotal regulator of the circadian clock. TDP-43 knockdown induces intracellular arrhythmicity, disrupts transcriptional activation regulation, and diminishes clock genes expression. Moreover, our experiments in adult mouse reveal that TDP-43 knockdown, specifically within the suprachiasmatic nucleus (SCN), induces locomotor arrhythmia, arrhythmic c-Fos expression, and depression-like behavior. This observation offers valuable insights into the substantial impact of TDP-43 on the behavioral aberrations associated with ALS/FTD. In summary, our study illuminates the significance of TDP-43 in circadian regulation, shedding light on the circadian regulatory mechanisms that may elucidate the pathological underpinnings of ALS/FTD.

Tenuigenin promotes non-rapid eye movement sleep via the GABAA receptor and exerts somnogenic effect in a MPTP mouse model of Parkinson's disease

Sleep disturbances are commonly non-motor symptoms in Parkinson's diseases (PD). However, standard dopamine replacement therapies for the treatment of motor symptoms often prove inadequate in combating sleep disturbances. Previous studies conducted by our research group have reported the neuroprotective effects of tenuigenin, a natural extract from Polygala tenuifolia root, which has been traditionally employed in treating insomnia. The objective of this study was to investigate the potential of tenuigenin in modulating sleep-wake behaviors and elucidate the underlying mechanisms. We employed EEG/EMG recordings to evaluate the impact of tenuigenin on sleep-wake profiles. Furthermore, we utilized c-Fos immunostaining, whole-cell patch clamping and local field potentials (LFP) recording to explore the mechanisms involved in sleep-promoting effects of tenuigenin. Additionally, we examined the effects of tenuigenin on sleep-promoting in MPTP PD mice. Here, we found tenuigenin demonstrated a significant increase in NREM sleep and a reduction in sleep latency in mice, without altering the EEG power density. Moreover, tenuigenin increased c-Fos expression in the ventrolateral preoptic area (VLPO) and stimulated sleep-promoting neurons in VLPO. The sleep-promoting effects of tenuigenin were abolished when mice were pretreated with flumazenil, an antagonist at the benzodiazepine site of the GABAA receptor. Furthermore, tenuigenin was found to ameliorate sleep disturbances in MPTP-induced mice. The results suggesting that tenuigenin facilitated a type of NREM sleep comparable to physiological NREM sleep through interaction with the GABAA receptor. Additionally, tenuigenin demonstrated improvements in sleep disturbances in MPTP-induced PD mice, suggesting its potential as a sleep-promoting substance, particularly for PD patients experiencing sleep disturbances.

Brain areas modulation in consciousness during sevoflurane anesthesia

Sevoflurane is presently one of the most used inhaled anesthetics worldwide. However, the mechanisms through which sevoflurane acts and the areas of the brain associated with changes in consciousness during anesthesia remain important and complex research questions. Sevoflurane is generally regarded as a volatile anesthetic that blindly targets neuronal (and sometimes astrocyte) GABAA receptors. This review focuses on the brain areas of sevoflurane action and their relation to changes in consciousness during anesthesia. We cover 20 years of history, from the bench to the bedside, and include perspectives on functional magnetic resonance, electroencephalogram, and pharmacological experiments. We review the interactions and neurotransmitters involved in brain circuits during sevoflurane anesthesia, improving the effectiveness and accuracy of sevoflurane's future application and shedding light on the mechanisms behind human consciousness.

Low frequency visual stimulation enhances slow wave activity without disrupting the sleep pattern in mice

Non-invasive stimulation technologies are emerging as potential treatment options for a range of neurodegenerative disorders. Experimental evidence suggests that stimuli-evoked changes in slow brain rhythms may mitigate or even prevent neuropathological and behavioral impairments. Slow wave activity is prevalent during sleep and can be triggered non-invasively by sensory stimulation targeting the visual system or directly via activation of neurons locally using optogenetics. Here, we developed new tools for delivering visual stimulation using light-emitting diodes in freely moving mice while awake and during sleep. We compared these tools to traditional optogenetic approaches used for local stimulation of neurons in the cerebral cortex. We then used these tools to compare the effects of low-frequency visual versus optogenetic stimulations on the slow wave activity and sleep pattern in mice. Visual stimulation effectively enhanced slow wave activity without disrupting the sleep pattern. Optogenetic stimulation of cortical GABAergic neurons increased NREM sleep. These results suggest that visual stimulation can be effective at boosting slow wave activity without having adverse effects on sleep and thus holds great potential as a non-invasive stimulation treatment strategy.

G protein-coupled estrogen receptor in the rostral ventromedial medulla contributes to the chronification of postoperative pain

Aims

Chronification of postoperative pain is a common clinical phenomenon following surgical operation, and it perplexes a great number of patients. Estrogen and its membrane receptor (G protein‐coupled estrogen receptor, GPER) play a crucial role in pain regulation. Here, we explored the role of GPER in the rostral ventromedial medulla (RVM) during chronic postoperative pain and search for the possible mechanism.

Methods and Results

Postoperative pain was induced in mice or rats via a plantar incision surgery. Behavioral tests were conducted to detect both thermal and mechanical pain, showing a small part (16.2%) of mice developed into pain persisting state with consistent low pain threshold on 14 days after incision surgery compared with the pain recovery mice. Immunofluorescent staining assay revealed that the GPER‐positive neurons in the RVM were significantly activated in pain persisting rats. In addition, RT‐PCR and immunoblot analyses showed that the levels of GPER and phosphorylated μ‐type opioid receptor (p‐MOR) in the RVM of pain persisting mice were apparently increased on 14 days after incision surgery. Furthermore, chemogenetic activation of GPER‐positive neurons in the RVM of Gper‐Cre mice could reverse the pain threshold of pain recovery mice. Conversely, chemogenetic inhibition of GPER‐positive neurons in the RVM could prevent mice from being in the pain persistent state.

Conclusion

Our findings demonstrated that the GPER in the RVM was responsible for the chronification of postoperative pain and the downstream pathway might be involved in MOR phosphorylation.

Revealing the Cortical Glutamatergic Neural Activity During Burst Suppression by Simultaneous wide Field Calcium Imaging and Electroencephalography in Mice

Burst suppression (BS) is an electroencephalogram (EEG) pattern in which signals alternates between high-amplitude slow waves (burst waves) and nearly flat low-amplitude waves (suppression waves). In this study, we used wide-field (8.32 mm × 8.32 mm) fluorescent calcium imaging to record the activity of glutamatergic neurons in the parietal and occipital cortex, in conjunction with EEG recordings under BS induced by different anesthetics (sevoflurane, isoflurane, and propofol), to investigate the spatiotemporal pattern of neural activity under BS. The calcium signal of all observed cortices was decreased during the phase of EEG suppression. However, during the phase of EEG burst, the calcium signal in areas of the medial cortex, such as the secondary motor and retrosplenial area, was excited, whereas the signal in areas of the lateral cortex, such as the hindlimb cortex, forelimb cortex, barrel field, and primary visual area, was still suppressed or only weakly excited. Correlation analysis showed a strong correlation between the EEG signal and the calcium signal in the medial cortex under BS (except for propofol induced signals). As the burst-suppression ratio (BSR) increased, the regions with strong correlation coefficients became smaller, but strong correlation coefficients were still noted in the medial cortex. Taken together, our results reveal the landscape of cortical activity underlying BS.

Central Neural Circuits Orchestrating Thermogenesis, Sleep-Wakefulness States and General Anesthesia States

Great progress has been made in specifically identifying the central neural circuits (CNCs) of the core body temperature (Tcore), sleep-wakefulness states (SWs), and general anesthesia states (GAs), mainly utilizing optogenetic or chemogenetic manipulations. We summarize the neuronal populations and neural pathways of these three CNCs, which gives evidence for the orchestration within these three CNCs, and the integrative regulation of these three CNCs by different environmental light signals. We also outline some transient receptor potential (TRP) channels that function in the CNCs-Tcore and are modulated by some general anesthetics, which makes TRP channels possible targets for addressing the general-anesthetics-induced-hypothermia (GAIH). We suggest this review will provide new orientations for further consummating these CNCs and elucidating the central mechanisms of GAIH.