Cerebellar Purkinje cell firing promotes conscious recovery from anesthesia state through coordinating neuronal communications with motor cortex

Systematic evaluation of adhesives for implant fixation in multimodal functional brain MRI

OBJECTIVE

Invasive multimodal fMRI in rodents is often compromised by susceptibility artifacts from adhesives used to secure cranial implants. We hypothesized that adhesive type, shape, and field strength significantly affect susceptibility artifacts, and systematically evaluated various adhesives.

MATERIALS AND METHODS

Thirty-one adhesives were applied in constrained/unconstrained geometries and imaged with T2*-weighted EPI at 7.0 and 9.4 T to assess artifact depths. Spherical and flat patch shapes, both unconstrained geometries, were compared for artifact depth in vitro and in vivo. Adhesion strength was assessed on post-mortem mouse crania. Finally, an integrative scoring system rated adhesive properties, including artifact depth, handling, and adhesion strength.

RESULTS

Susceptibility artifacts were two times larger at 9.4 than at 7.0 T (p < 0.001), strongest at the patch edges, and deeper with spherical than flat patches (p < 0.05). Artifact size depended more on shape and volume after curing than adhesive type. Our integrative scoring system showed resins, bonding agents, and acrylics offered the best overall properties, while silicones and cements were less favorable.

DISCUSSION

Adhesive selection requires balancing handling, curing time, strength, and artifact depth. To minimize artifacts, adhesives should be applied in a spread-out, flat and thin layer. Our integrative scoring system supports classification of future classes of adhesives.

Noradrenergic Locus Coeruleus-CA3 Activation Alleviates Neuropathic Pain and Anxiety- and Depression-Like Behaviors by Suppressing Microglial Neuroinflammation in SNI Mice

OBJECTIVE

Neuropathic pain (NP) arises from neuroimmune interactions following nerve injury and is often accompanied by anxiety and depression. The aim of the study is to evaluate the effects of the noradrenergic locus coeruleus (LC), a key regulator of pain and emotional states, projects extensively to the hippocampus.

METHOD

We investigated the effects of chronic NP on LC integrity and its projections to the hippocampal CA3 region in spared nerve injury (SNI) mice with behavioral tests, immunohistochemistry, neurochemical analyses, and Gq-DREADD.

RESULTS

Chronic NP induced LC neuronal loss, reduced hippocampal norepinephrine (NE) release, and triggered microglial activation and neuroinflammation in CA3. Selective activation of LC-CA3 noradrenergic neurons using Gq-DREADD chemogenetics alleviated NP and comorbid anxiety- and depression-like behaviors. This intervention suppressed microglial activation, decreased proinflammatory cytokines (TNF-α and IL-1β), and restored NE levels in CA3.

CONCLUSION

Our findings highlighted the therapeutic potential of targeting LC-CA3 projections to mitigate chronic NP and its neuropsychiatric comorbidities via modulation of hippocampal neuroinflammation.

Mettl3-m6A-NPY axis governing neuron-microglia interaction regulates sleep amount of mice

Sleep behavior is regulated by diverse mechanisms including genetics, neuromodulation and environmental signals. However, it remains completely unknown regarding the roles of epitranscriptomics in regulating sleep behavior. In the present study, we showed that the deficiency of RNA m6A methyltransferase Mettl3 in excitatory neurons specifically induces microglia activation, neuroinflammation and neuronal loss in thalamus of mice. Mettl3 deficiency remarkably disrupts sleep rhythm and reduces the amount of non-rapid eye movement sleep. We also showed that Mettl3 regulates neuropeptide Y (NPY) via m6A modification and Mettl3 conditional knockout (cKO) mice displayed significantly decreased expression of NPY in thalamus. In addition, the dynamic distribution pattern of NPY is observed during wake-sleep cycle in cKO mice. Ectopic expression of Mettl3 and NPY significantly inhibits microglia activation and neuronal loss in thalamus, and restores the disrupted sleep behavior of cKO mice. Collectively, our study has revealed the critical function of Mettl3-m6A-NPY axis in regulating sleep behavior.

The regulation of glutamatergic nervous system in sleep-wake states and general anesthesia

The sleep-wake states and general anesthesia share many neurophysiological similarities, as both involve reversible changes in consciousness and modulation of brain activity. This paper reviews the role of glutamatergic neurons, the brain's primary excitatory neurons, in regulating sleep-wake states and general anesthesia. We discuss the involvement of glutamatergic neurons across various brain regions, including the brainstem, basal forebrain, thalamus, hypothalamus, and cortex, highlighting their contributions to physiological sleep-wake and anesthesia modulation. Recent advancements in techniques such as optogenetics, chemogenetics, and neural tracing have enhanced our understanding of these neurons' functions. Understanding these mechanisms can lead to improved therapeutic strategies for sleep disorders and more precise anesthetic practices, providing new avenues for clinical intervention.

Neurobiological basis of emergence from anesthesia

The suppression of consciousness by anesthetics and the emergence of the brain from anesthesia are complex and elusive processes. Anesthetics may exert their inhibitory effects by binding to specific protein targets or through membrane-mediated targets, disrupting neural activity and the integrity and function of neural circuits responsible for signal transmission and conscious perception/subjective experience. Emergence from anesthesia was generally thought to depend on the elimination of the anesthetic from the body. Recently, studies have suggested that emergence from anesthesia is a dynamic and active process that can be partially controlled and is independent of the specific molecular targets of anesthetics. This article summarizes the fundamentals of anesthetics' actions in the brain and the mechanisms of emergence from anesthesia that have been recently revealed in animal studies.