The suprachiasmatic nucleus (SCN) of the hypothalamus serves as the master circadian pacemaker that synchronizes internal rhythms with the environmental light-dark (LD) cycle. Although SCN spike activity is crucial for maintaining circadian rhythms, there is a scarcity of long-term in vivo electrophysiological recording data, especially for ultradian cycles. Using long-term extracellular single-unit recordings in anesthetized rats, we discovered that multiple types of ultradian cycles, which beyond the three previously reported types, can coexist within a single SCN neuron. The period of these ultradian cycles in one single neuron may shift from nearly 2 min to around 10, 30 or around 80 min, or vice versa. These dynamic changes suggest that periodic stimuli may be particularly suitable for probing the electrical characteristics of SCN neurons. We therefore applied periodic light stimulation in anesthetized rats and performed spectral analysis for neuronal activity. We found that SCN neurons can be entrained by short-period LD cycles ranging from seconds to minutes. Notably, the induced oscillatory firing patterns persisted for more than 1.5 h after stimulus cessation, suggesting persistent reverberatory activity within SCN circuitry. The correlation between firing during and after stimulation increased with stimulus duration and cycle number, suggesting that stronger or longer LD exposure may reinforce post-stimulus oscillatory activity. Moreover, light-on cells exhibited more robust post-stimulus oscillations than light-off cells, implying potentially differential roles in photic encoding. These results suggest periodic light changes can induce persistent rhythmic electrical activity within SCN neurons, potentially reflecting a previously unrecognized form of sub-circadian plasticity within the SCN. We propose an "incomplete gear" model as a hypothetical framework for interpreting temporal dynamics in the SCN. In this framework, SCN neurons exhibit variable ultradian cycle periods, which can be conceptualized as a "incomplete gear" with heterogeneous tooth pitches. Periodic light exposure may bias SCN neuronal activity toward shorter or longer ultradian cycles, and the accumulation of these shifts could contribute to changes in the overall periodicity of neuronal activity, potentially contributing to broader temporal reorganization within SCN networks.
Alterations in cortical somatostatin (SST)-containing GABAergic interneurons are among the most consistently replicated molecular findings in schizophrenia. Whether these alterations primarily reflect intrinsic cellular vulnerabilities, regional circuit context, or an interaction between the two remains unclear. To address this question, we examined a transcriptionally distinct SST neuron subtype that selectively expresses chondrolectin (CHODL), referred to as CHODL-SST neurons, across two brain regions with markedly different circuit organization: deep layer 6 and adjacent subcortical white matter of the dorsolateral prefrontal cortex (DLPFC) and the caudate nucleus.Using multiplex fluorescent in situ hybridization in postmortem tissue from 18 matched pairs of schizophrenia and unaffected comparison individuals, we quantified mRNA levels of CHODL, SST, neuropeptide Y (NPY), and nitric oxide synthase (NOS1) within CHODL-SST neurons in both regions.In the DLPFC, CHODL-SST neurons exhibited lower mRNA levels for all four transcripts in schizophrenia, with small-to-medium effect sizes (-0.29 to -0.52). In contrast, effect sizes in the caudate were nominal (-0.13 to 0.03), with Bayesian analyses providing strong evidence for no difference in schizophrenia. For every transcript, a significant diagnosis-by-region interaction (all p < 0.005) highlighted a striking dissociation between cortical and striatal CHODL-SST neurons.These findings indicate that schizophrenia-associated molecular alterations in CHODL-SST neurons are regionally selective and preferentially affect cortical populations. Rather than reflecting uniform cell-intrinsic vulnerability, these results support a model in which differential vulnerability emerges from the interaction between subtype-specific molecular features and regional circuit context, with implications for understanding SST neuron dysfunction and developing circuit-informed therapeutic strategies.
Rodent cell culture models have long underpinned research into nociceptive signaling; however, their limited recapitulation of human nociceptor biology has created a translational gap in analgesic development. While primary human sensory neurons are relevant, their use is hampered by scarcity, ethical constraints, donor variability, and difficulties in long-term culture. Furthermore, conventional cultures lack the compartmentalization needed to study sensory neuron processes and fail to recapitulate the synaptic connectivity between sensory and spinal cord neurons, limiting their translational relevance. To address these limitations, we utilized a microfluidic platform enabling compartmentalized culture of human induced pluripotent stem cell (hiPSC) derived sensory neurons (hiPSC-SNs) to study the function of their processes. We also demonstrate the feasibility of microfluidic co-cultures of hiPSC-SN with human iPSC-derived cortical excitatory neurons (hiPSC-CNs) as a basis for future development of models for sensory-to-CNs communication circuit. Using optimized protocols, we maintained stable microfluidic cultures and confirmed expression of pain-relevant sodium channels (Nav1.7, Nav1.8) in hiPSC-SN in both mono- and co-culture configurations. Leveraging this compartmentalized platform, we demonstrate that pharmacological blockade of Nav1.7 and Nav1.8 inhibits signal propagation along sensory neuron processes. We also demonstrate that growth factors modulate excitability of these processes. This functional validation underscores the platform's capability to investigate signal transmission along human sensory processes and demonstrates its potential for modelling more complex cellular interactions. Thus, we present a human iPSC-based microfluidic culture model that enables detailed study of sensory neuron processes and assessment of analgesics targeting nociceptive transmission, offering a significant advance toward analgesic drug discovery.
Neurons accumulate somatic mutations with age, but how mutation processes vary among neuronal types remains unclear. Characterizing this variability may elucidate the role of genome integrity in brain function and disease and reveal determinants of mutation rates and patterns. Using high-fidelity duplex DNA sequencing, we profiled somatic mutations across the lifespan in human cerebellar Purkinje and granule neurons, which differ markedly in size and physiology. Surprisingly, they exhibited similar substitution rates, including rates of SBS5, the body's predominant mutational signature, whose mechanism is unknown. However, their substitution patterns and insertion/deletion rates and patterns differed, with transcription associated with these differences. In surviving granule neurons from five cerebellar ataxias, we detected only a small disease effect on mutation profiles. Our work indicates that neuronal types can differ in aging-related mutagenesis and that key features distinguishing Purkinje and granule neurons are unlikely, in these neurons, to be major determinants of SBS5 activity.
Successful repair after brain injury requires a chain of events, including the generation, migration, and successful integration of adult-born neurons into preexisting circuits. In mammals, the capacity for neuronal regeneration is extremely limited and further declines with age, constraining recovery. Regeneration-competent vertebrates offer a unique opportunity to uncover mechanistic principles of seamless brain repair. We here introduce the African turquoise killifish, a naturally short-lived vertebrate in which tissue repair occurs at young but not old age. We established an integrative approach combining i) an optimized retroviral vector application to birthdate GFP-labeled dividing neural stem cells and their progeny, ii) targeted electrophysiology to quantify synaptic and intrinsic maturation of such neurons, and iii) a conditioned avoidance assay to track recovery of learned behavior in adult killifish. We applied this workflow to the dorsomedial telencephalon, a region homologous to the mammalian amygdala. We reveal that injury-induced adult-born neurons survive, mature, and integrate synaptically into preexisting circuits, and that this coincides with the recovery of learned avoidance behavior by two months postinjury. Only when newborn neurons display mature morpho-electric properties, including complex dendritic arborization and abundant dendritic spines, recovery of behavior is accomplished. That full functional recovery takes around 50 d, substantially longer than previously inferred from histological analyses alone, is a striking finding given the killifish's short lifespan. These findings establish the killifish as a powerful vertebrate model and introduce a scalable platform for experimentally manipulating neuronal maturation and integration in vivo, particularly in the context of aging and age-related regenerative decline.
N6-methyladenosine (m6A) facilitates functional recovery following ischemic stroke (IS). This study investigated the role of Sptbn2 in post-stroke cognitive impairment (PSCI) and the mechanisms regarding m6A. HT-22 cell damage and ferroptosis were analyzed following OGD exposure. pMCAO surgery was performed to establish an IS mouse model. We assessed neurological deficits and cognitive impairment in mice using the mNSS, adhesive removal test, rotarod test, novel object recognition test, and Y-maze test. Adeno-associated viral vectors with overexpression of Sptbn2 combined with pMCAO surgery were used to analyze cognitive dysfunction and ferroptosis. Sptbn2 was reduced in neurons of PSCI mice. Sptbn2 overexpression alleviated ferroptosis-induced neuronal damage by promoting the membrane translocation of Slc7a11. Hnrnpa2b1 promoted Sptbn2 stability through an m6A-related mechanism. Knockdown of Sptbn2 reversed the mitigation of ferroptosis by Hnrnpa2b1 and exacerbated the neuronal injury. Under OGD, Bard1 knockdown reduced the Hnrnpa2b1 ubiquitination, slowed Hnrnpa2b1 degradation, and restored Sptbn2 expression. Knockdown of Bard1 alleviated neuronal ferroptosis, thereby reducing the development of cognitive impairment in mice, a phenotype reversed by Hnrnpa2b1 or Sptbn2 knockdown. In IS, Bard1-associated regulation of Hnrnpa2b1 ubiquitination is accompanied by reduced Sptbn2 expression and impaired Slc7a11 membrane translocation, and is involved in neuronal ferroptosis-related damage.
Stress triggers a complex network of neuroendocrine, immune, and behavioral responses aimed at maintaining homeostasis. Nesfatin-1, a hypothalamic peptide initially identified for its anorexigenic effects, has also been increasingly implicated in stress-related processes. This study investigated whether acute inflammatory stress induced by lipopolysaccharide (LPS) activates Nesfatin-1 neurons in the supraoptic nucleus (SON) and examined the modulatory role of glutamatergic receptor antagonists. Female and male Sprague-Dawley rats were assigned to control, LPS, MK-801 + LPS, and CNQX + LPS groups. Neuronal activation was assessed using dual immunohistochemical staining for c-Fos and Nesfatin-1, followed by quantitative analysis of co-localized neurons in the SON. LPS administration significantly increased the proportion of c-Fos-positive Nesfatin-1 neurons in both female and male rats compared to controls (p = 0.001). Pretreatment with MK-801 and CNQX attenuated this activation (p < 0.01), indicating the involvement of both NMDA and non-NMDA glutamatergic pathways. Acute inflammatory stress activates Nesfatin-1 neurons in the SON, and this response is modulated by glutamatergic signaling. These findings provide new immunohistochemical evidence linking glutamatergic transmission to stress-induced Nesfatin-1 activation, with potential implications for the neurobiological interaction between inflammation, energy homeostasis, and stress-related processes.
Spinal muscular atrophy (SMA) results from biallelic loss of functional survival motor neuron 1 (SMN1), reducing production of full-length survival motor neuron (SMN) protein and leaving endogenous SMN supply largely dependent on inefficient survival motor neuron 2 (SMN2) splicing. This review conceptualizes SMA as a disorder in which available SMN supply fails to meet tissue- and stage-specific SMN requirement, defined as the minimum effective SMN level needed to maintain normal cellular or tissue function. Disease-modifying therapies (DMTs) have transformed SMA outcomes, particularly when initiated presymptomatically or very early after symptom onset. However, treatment responses remain heterogeneous, especially among infants with two SMN2 copies and patients treated after symptomatic progression. These observations suggest that therapeutic response is shaped not only by SMN restoration but also by timing, residual SMN reserve, and tissue vulnerability already present at treatment initiation. This review argues that SMN requirement varies across tissues, developmental stages, and biological states. It proposes a three-component framework: developmental mismatch, post-developmental dynamic mismatch, and tissue-state transitions. Developmental mismatch is the most directly supported component and highlights tissue- and stage-specific vulnerability before and shortly after birth, particularly in the motor unit; early SMN insufficiency may leave latent developmental vulnerability even after early DMT. Post-developmental dynamic mismatch is presented as an evidence-informed, hypothesis-generating extension in which constrained SMN supply may be sufficient at baseline but inadequate during maintenance, remodeling, repair, intercurrent illness, or catabolic stress. Tissue-state transitions distinguish preserved tissue, functionally impaired but structurally retained tissue, and structurally degenerated tissue with limited reversibility. Together, this framework may help interpret residual deficits after early treatment, incomplete recovery after delayed treatment, and the need for multimodal biomarkers and longitudinal monitoring strategies that distinguish potentially reversible functional impairment from structural degeneration with limited reversibility.
While the recent clinical approval of amyloid-targeting monoclonal antibodies represents a landmark in Alzheimer's disease (AD) management, these immunotherapies fundamentally function as agents of mitigation rather than restoration, failing to reconstitute decimated neural circuitry. Direct in situ astrocyte-to-neuron reprogramming offers a compelling regenerative alternative by leveraging the abundant endogenous glial reservoir. However, translating this cellular plasticity in vivo is severely bottlenecked by the hostile pathological microenvironment and the deeply entrenched epigenetic memory of reactive astrocytes. In this review, we delineate a tripartite neuroregenerative framework. First, we evaluate the prerequisite use of senotherapeutics to engineer a permissive parenchymal niche for nascent neuronal survival. Second, we explore epigenomic editing strategies-including CRISPR-dCas9 platforms and targeted pharmacological modulators-required to dismantle repressive heterochromatin and unlock sequestered neurogenic loci. Third, we dissect the molecular execution of reprogramming via pioneer transcription factors (TFs), emphasizing the obligatory metabolic rewiring from astrocytic glycolysis to neuronal oxidative phosphorylation (OXPHOS). Finally, to overcome formidable translational hurdles, we highlight the convergence of AI-optimized lipid nanoparticles (LNPs) for non-viral blood-brain barrier (BBB) transcytosis alongside Neurological Digital Twins (NDTs) to computationally predict the optimal presymptomatic intervention window. By harmonizing microenvironmental conditioning, epigenetic rejuvenation, and precision delivery, this systems-level blueprint provides a promising rationale for transitioning AD therapeutics from passive deceleration to active structural restoration.
The primary aim was to explore the relationship between neck weakness in people with motor neurone disease (MND) and their respiratory function. The secondary aim was to identify whether neck weakness can be a prognostic factor. This was a retrospective observational cohort study. Data was collected from patient records on MND characteristics, neck weakness, respiratory function, and noninvasive ventilation (NIV) use. Multivariate modeling explored the effect of neck weakness on respiratory variables. MND-related neck weakness was evident in 41% of 324 participants. Fifty-four percent used NIV and 17% became dependent on NIV during disease progression. The presence of neck weakness in MND was predictive of time to respiratory function decline, for respiratory outcomes (forced vital capacity (FVC) <65%, FVC <50% and NIV use) as well as having an effect on time to death. Median time from neck weakness onset to death was 8 months (IQR 10 months; range 0 to 60 months) with bulbar onset the quickest, median of 7 months (IQR 7 months, range 0 to 43 months). The presence of neck weakness is associated with a more rapid respiratory function decline in MND. In addition, neck weakness can be considered a prognostic factor in MND survival. People with motor neurone disease (MND) experience weakness in different parts of their body including muscles that are responsible for breathing. As the disease worsens, it is expected that their breathing worsens, resulting in death. To help prolong the person’s life, timely equipment that makes breathing easier is important. It is thought that there may be a relationship between weakness spreading to the neck muscles and the person’s ability to breathe and whether it could help predict how the disease will progress. To explore this further, we reviewed the medical records of 324 people with MND. We found that about 4 in 10 people had neck weakness from their MND and over half were using breathing support. We also found that those with neck weakness tended to lose their breathing function more quickly and needed breathing support sooner. People with neck weakness were also found to have a shorter survival time, with an average of 8 months once their neck weakness began, however this varied depending on the type of MND the person had.
To investigate whether selected Malaysian plant extracts modulate the antioxidant-autophagy axis to enhance neuronal and skeletal muscle protection. Four standardized extracts (Persicaria minor, Eurycoma longifolia (EL), Labisia pumila, and Ipomoea aquatica) were evaluated for antioxidant activity at 100, 200, and 300 μg/mL using ABTS, DPPH, and ORAC assays. The most active extract was further examined in SH-SY5Y neuronal-like cells and differentiated C2C12 myotubes. Cell viability was assessed using CCK-8, oxidative DNA damage was measured by 8-OHdG ELISA, and autophagy-related changes were evaluated by LC3/p62 immunofluorescence and western blot analysis of LC3-II and p62 with chloroquine (CQ) as a lysosomal inhibitor. Among the four extracts, EL exhibited the strongest antioxidant activity, achieving the highest values in ABTS (107.59 ± 7.98 μmol Trolox/g), DPPH (27.28 ± 1.29 μmol Trolox/g), and ORAC (81.12 ± 4.81 μmol Trolox/g) at 300 μg/mL, also showing the lowest IC₅₀ (167.22, 97.64, and 67.90 μg/mL for ABTS, DPPH, and ORAC, respectively), with regression analyses confirming significant dose-response relationships (R² > 0.96, p < 0.05). CCK-8 analysis showed that EL at 100-300 μg/mL did not cause overt cytotoxicity in either cell model after 24 h treatment (p > 0.2), whereas the positive cytotoxicity control markedly reduced viability (p < 0.001). 8-OHdG ELISA showed that EL reduced oxidative DNA damage, with significant reductions at 200 and 300 μg/mL in both SH-SY5Y and C2C12 cells (p < 0.05). H2O2 markedly increased 8-OHdG levels in both models (p < 0.001). Immunofluorescence analysis showed concentration-dependent modulation of LC3 and p62 autophagy-related markers. In SH-SY5Y cells, treatment with EL induced a dose-dependent increase in LC3 puncta (p < 0.001) and a significant reduction in p62 fluorescence (p < 0.01). Similar trends were observed in C2C12 myotubes, where LC3 puncta formation was enhanced (p < 0.05), and p62 levels decreased (p < 0.01). Western blot validation further showed that EL increased LC3-II abundance and that EL + CQ further increased LC3-II accumulation compared with CQ alone, particularly at 300 μg/mL (p < 0.05). p62 decreased under basal EL treatment but showed a non-canonical decrease in the CQ-only group and was therefore interpreted cautiously. EL showed the strongest antioxidant activity among the tested Malaysian plant extracts and modulated autophagy-related cellular markers without overt cytotoxicity. These findings identify EL as a promising candidate for further investigation in oxidative stress- and proteostasis-related cellular protection.
The ketogenic diet is used to treat drug-resistant epilepsy, yet the molecular mechanisms coupling metabolic state to seizure suppression remain understudied. β-Hydroxybutyrate (β-HB), a principal ketone body, exerts antiseizure effects, yet its downstream ionic mechanisms remain unclear. We used 69 C57BL/6 mice, including males and females (4-week-old for ex vivo electrophysiology and calcium imaging and 8-week-old for in vivo seizure experiments). β-HB or saline was administered after the onset of status epilepticus, induced in mice by continuous hippocampal stimulation. Intrinsic excitability and excitatory synaptic currents on hippocampal granule cells were measured using the patch clamp technique. Calcium imaging was performed after viral delivery of a genetically encoded calcium indicator into the hippocampus. In vivo, β-HB rapidly reduced the duration of status epilepticus. At the cellular level, patch-clamp recordings showed that β-HB hyperpolarized dentate granule cells (DGCs) increased action potential threshold and reduced firing frequency. Moreover, β-HB suppressed excitatory synaptic transmission onto DGCs. At the network-level, β-HB perfusion significantly decreased DGC population activity by reducing neuronal excitability and excitatory synaptic currents. Mechanistically, pharmacological blockade of G protein-gated inwardly rectifying potassium (GIRK) channels prevents the β-HB-induced suppression of DGC intrinsic excitability, excitatory synaptic transmission, and population-level activity. In contrast, inhibition of adenosine triphosphate-sensitive potassium channels had no detectable impact on β-HB-mediated modulation of DGC intrinsic excitability or network responses. These findings identify GIRK channels as a key downstream effector of β-HB signaling, providing a mechanistic link between ketogenic states and neuronal excitability, revealing a new mechanistic target for ketogenic therapies.
Type 2 ryanodine receptor (RyR2), a Ca2+ release channel located in the endoplasmic reticulum (ER) membrane, expresses catecholamine-induced polymorphic ventricular tachycardia (CPVT), and is a potential risk factor of autism spectrum disorder (ASD). However, the pathological relationship between RyR2 mutation-induced Ca2+ dysregulation and ASD pathology remains unclear. This study examined the association between CPVT-related RyR2 mutations and ASD pathology to determine its dopaminergic pathological role in ASD. Patient-derived stem cells from human exfoliated deciduous teeth were obtained from a boy with comorbid CPVT and ASD, and differentiated to dopaminergic neurons (RyR2-DNs). Two heterozygous missense mutations were identified in RyR2: c.9910C > G, p.Q3304E in exon 69 and c.14222C > T, p.A4741V in exon 99 (RyR269/99). RyR2-DNs showed cytosolic and mitochondrial Ca2+ accumulation, and impaired neurite outgrowth, suggesting that RyR269/99 is a gain-of-function mutation that promotes Ca2+ release from the ER and attenuates neurite development. RyR2-DNs also exhibited increased mitochondrial reactive oxygen species along with impaired mitochondrial oxidative phosphorylation. These mitochondrial abnormalities and neurite outgrowth were managed by pharmacological intervention of mitochondrial Ca2+ accumulation. Thus, RyR2 hyper-activation-induced mitochondrial Ca2+ overload may cause oxidative stress-related mitochondrial dysfunction, impairing DN development and dopaminergic dysregulation in ASD.
Epilepsy is a chronic neurological disorder characterized by recurrent seizures, neuroinflammation, and epigenetic instability, with around one-third of patients experiencing drug-resistant epilepsy. While ion channels and neurotransmitter imbalances have been thoroughly examined in relation to epilepsy, the significance of piRNAs and their interaction with PIWI proteins in gene regulation, transposon silencing, and inflammatory signaling inside the epileptic brain is gaining recognition. This summary encapsulates the existing understanding of piRNA synthesis, the epigenetic control through PIWI-piRNA interactions, and their novel roles in epileptogenesis. PIWI-piRNA complexes target highly expressed genomic areas, such as LINE-1 retrotransposons, and mute them by recruiting chromatin modifiers such DNMT3A and H3K9 methyltransferase complexes, therefore influencing genome stability and neuronal excitability. Additionally, piRNAs initiate pathways associated with neuroinflammation, including the activation of the Toll-like receptor-4/NF-kB signaling pathway and the NLRP3 inflammasome, and indirectly influence GABAergic homeostasis through interactions with the extensive noncoding RNA regulatory network. Targeted modulation of kainic acid, pilocarpine, and hereditary epilepsy models has been documented to provide decreases in seizure load; however, the extent of this effect varies among the models and modulation techniques employed. The review critically evaluates emerging therapeutic strategies, including AAV9 vectors, lipid nanoparticles, exosome-based delivery systems, and antisense oligonucleotides, along with their associated challenges such as blood-brain barrier penetration, off-target effects, immune activation, and long-term safety. In conclusion, the PIWI-piRNA axis represents a potential yet nascent domain for biomarker creation and disease modulation in epilepsy.
The dynamical behaviour of a population-based rate model with firing adaptation is studied. An excitatory and inhibitory population of neurons is recurrently coupled and a negative feedback term is added to the excitatory population as firing adaptation. In several studies of these models, the UP-DOWN transitions are in focus, which are also exhibited by the investigated model. In this paper we provide a full characterization of equilibrium points with the precise conditions for their existence and stability. Calculations can be performed analytically and explicit formulas can be provided due to the fact that the activation function is a threshold linear function. We use bifurcation analysis to detect significant changes in the phase space. Complete list of bifurcation diagrams is provided with respect to the number of steady states. Oscillatory dynamics of neurobiological relevance are examined through local bifurcation analysis. The study demonstrates that sharp wave-ripple oscillations may emerge in certain regions of the parameter space.
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Parkinson's disease is characterized by dopaminergic neuron loss and accumulation of α-synuclein aggregates in the brain. G51D α-synuclein knock-in mice provide a genetically and clinically relevant model of disease, exhibiting early olfactory deficits, age-dependent motor impairment, and progressive phospho-α-synuclein accumulation. In multiple Parkinson's disease models, striatal cholinergic and parvalbumin interneurons, as well as astrocytes, lose primary cilia and the neurotrophic signaling needed to sustain dopaminergic neurons. We show here that G51D α-synuclein mice share these phenotypes. Phospho-Ser129 α-synuclein accumulation correlates with cilia loss in cholinergic interneurons but not in spiny projection neurons that accumulate higher phospho-α-synuclein levels. In the piriform cortex, parvalbumin neurons lose primary cilia and downregulate Neurturin, potentially contributing to olfactory dysfunction. Within the peripheral olfactory epithelium, horizontal basal cells lose cilia, whereas multiciliated olfactory sensory neuron cilia remain intact. These findings reveal convergent cellular vulnerabilities across Parkinson's disease models and highlight a pathogenic role for impaired ciliary signaling.
Peripheral sensory signaling in homeothermic mammals is a thermally constrained process where prolonged exposure to temperatures below 10°C disrupts neurotransmission and may incur irreversible nerve damage. The hibernating thirteen-lined ground squirrel (Ictidomys tridecemlineatus) preserves somatosensory function during torpor at near-freezing body temperatures through unknown mechanisms. We show that, despite prolonged hypothermia during torpor, squirrel dorsal root ganglion (DRG) neurons maintain membrane potential and excitability. Furthermore, DRG neurons from torpid hypothermic squirrels show potentiated mechanotransduction compared with neurons from active euthermic animals. Cold exposure is necessary and sufficient to enhance mechanotransduction in squirrel neurons, demonstrating that peripheral sensory neurons possess a cell-intrinsic capacity to undergo reversible functional adaptation to changes in ambient temperature. Finally, we show that a single light tactile stimulus is sufficient to trigger arousal from torpor, demonstrating the preservation of mechanosensory signaling beyond the peripheral nervous system in torpid animals below 5°C. Our work reveals a temperature-gated neuronal mechanism underlying cold-resistant mechanosensation and underscores the adaptability of mammalian peripheral nervous system function under extreme thermal conditions.
Improving behavioral performance relies on the ability to associate decisions with their positive and negative outcomes. Although neurons that associate actions with their consequences have been identified across multiple brain regions, the circuit-level mechanisms underlying this integration remain poorly understood. Here, using an operant thermoregulatory assay in larval zebrafish, we show that the dorsal habenula-interpeduncular nucleus (dHb-IPN) pathway is necessary for associating actions with subsequent thermal reward. A population of intermediate IPN (iIPN) neurons encodes actions only when they lead to reward, suggesting a role in establishing action-outcome associations. This integration is temporally precise, requiring actions and their outcomes to occur within approximately one second in both the behavioral assay and iIPN responses. We then combine circuit mapping and axon imaging to show that actions and reward signals are conveyed by GABAergic prepontine and glutamatergic dHb neurons, respectively. Finally, the integration between action and reward signals relies on presynaptic GABAB receptor-mediated modulation of dHb axon terminals by prepontine neurons. These results link a crucial computation for adaptive behavior to a specific circuit mechanism.
Excessive microglial activation after subarachnoid hemorrhage (SAH) contributes to early brain injury (EBI) and poor clinical outcomes. This study explores the role of complement C3a receptor 1 (C3aR1) in microglial activation after SAH and evaluates Vorinostat as a potential therapeutic agent. Differentially expressed genes were identified from GEO datasets (GSE36791, GSE73378), followed by WGCNA and machine learning to pinpoint key SAH-related genes. Molecular docking and molecular dynamics simulation identified Vorinostat as a potential C3aR1-targeting compound. Functional studies were conducted using C3aR1 knockout mice and BV2 microglial cells. Neurological outcomes were assessed through Garcia score, rotarod, and pole tests. Histological staining and immunofluorescence evaluated neuronal injury and microglial activation. ELISA was used to measure plasma C3aR1 and inflammatory markers in SAH patients and correlate them with 6-month modified Rankin Scale (mRS) scores. C3aR1 was identified as a key SAH-related gene and was significantly upregulated after SAH. C3aR1 deficiency alleviated brain edema, neuronal apoptosis, neuroinflammation, and neurological dysfunction in SAH mice. Transcriptomic and functional analyses demonstrated that these protective effects were mediated, at least in part, through activation of the TGF-β/Smad signaling pathway. In vitro, C3aR1 knockdown suppressed microglial proliferation, migration, phagocytosis, and inflammatory responses, while reducing oxidative stress in co-cultured neurons; opposite effects were observed following C3aR1 overexpression. Vorinostat exhibited strong binding affinity to C3aR1, reduced C3aR1 protein expression, activated TGF-β/Smad signaling, and attenuated EBI after SAH. Clinically, plasma C3aR1 levels were significantly elevated in SAH patients, correlated with inflammatory cytokines and 6-month modified Rankin Scale scores, and independently predicted poor functional outcomes. C3aR1 promotes microglial overactivation and neuronal injury after SAH, partly via suppression of TGF-β signaling. Vorinostat attenuates EBI and is associated with reduced C3aR1 expression. Plasma C3aR1 may serve as a prognostic biomarker in SAH.