Search Results (232)

Background: Glucagon-like peptide-1 receptor (GLP1R) agonists, particularly semaglutide, show neuroprotective effects in genetic models of Alzheimer’s disease (AD). However, their delayed and long-term effects in sporadic AD, such as the intracerebroventricular streptozotocin (STZ) injection, remain insufficient. It is unclear how long the effects of GLP1R agonists persist after discontinuation and whether a single course can suppress progressive neurodegeneration. This study aimed to evaluate the delayed effects of semaglutide administration on morphological changes in neurons and glial cells in the hippocampus associated with cognitive impairment in an STZ-induced rat model of AD. Methods: Rats received bilateral intracerebroventricular STZ injections (3 mg/kg) followed by a 5-week course of intraperitoneal administration of semaglutide (0.1 mg/kg, every other day), and were euthanized 60 days after discontinuation of semaglutide administration. Immunomorphological methods were used to detect neuronal, astrocytic and microglial alterations. A novel object recognition test was performed to assess behavioral effects. Results: STZ-treated animals demonstrated cognitive impairments, ventriculomegaly, a significant increase in p-tau protein fluorescence intensity (p = 0.02), a decrease in CA1–CA3 field area (by 23%, p = 0.008), and reduced hippocampal neuronal density. Decreases in TOMM20 (mitochondrial marker) and synaptophysin levels were accompanied by significant glial activation in the hippocampal CA3 field. Semaglutide administration significantly reduced the enlarged ventricular lumen (by 43.5%), decreased p-tau fluorescence intensity, reduced vimentin-positive reactive astrocytes (by 68.4%), and increased synaptophysin fluorescence intensity. Furthermore, it reduced microglial activation (decreasing IBA1 cell density and elongation) and alleviated the disrupted AQP4 distribution. However, semaglutide did not completely halt the neurodegenerative process and showed no effect on the number of doublecortin-positive cells in the dentate gyrus. Conclusions: Hippocampal changes assessment revealed that course administration of semaglutide exerts prolonged effects, attenuating the severity of pathomorphological alterations and behavioral changes in a sporadic AD model after drug discontinuation. Full article

Viral infections of the central nervous system produce memory impairment through mechanisms that extend beyond acute neuronal injury. Herpes simplex virus type 1, human immunodeficiency virus, varicella zoster virus, cytomegalovirus, Epstein–Barr virus, influenza, SARS-CoV-2, West Nile virus, and Zika virus each enter or engage the brain through distinct routes, yet converge on four shared molecular pathways that selectively damage hippocampal circuits: mitochondria-associated membrane (MAM) dysfunction, chronic neuroinflammation, blood–brain barrier (BBB) disruption, and impaired CREB-BDNF signaling. These pathways specifically compromise the dentate gyrus, CA3, and CA1 subfields, producing predictable deficits in pattern separation, associative retrieval, and temporal memory binding. Antiretroviral and antiviral therapies suppress viral replication but fail to reverse organelle-level dysfunction, leaving most hippocampal injury unaddressed. Emerging plasma biomarkers, p-tau217, neurofilament light chain, and GFAP, combined with hippocampal subfield MRI, now enable mechanistic stratification before irreversible circuit loss occurs. This review proposes, as a unifying hypothesis, that virus-associated memory impairment represents a convergent hippocampal syndrome driven by shared downstream pathways, and that combination therapies targeting these pathways simultaneously offer greater therapeutic promise than pathogen-specific approaches alone. The evidentiary basis for this framework varies across pathogens and conditions; direct mechanistic evidence, mechanistic analogy, and preclinical data are distinguished throughout. Full article

Prenatal exposure to ionizing radiation is a known risk factor for neurodevelopmental deficits; however, the molecular mechanisms linking chronic embryonic insult to abnormal brain development remain poorly understood. This study investigated the long-term consequences of chronic prenatal gamma irradiation throughout gestation in C57BL/6 mice. Behavioural analysis of adult offspring revealed a specific increase in depression-like behaviours, with no significant alterations in anxiety or general exploratory activity. Immunohistochemical assessment demonstrated a significant reduction in adult hippocampal neurogenesis, marked by decreased doublecortin (DCX)-positive newborn neurons in the subgranular zone and fewer NeuN-positive mature neurons in the dentate gyrus hilus. Integrated RNA-seq, qPCR, and Western blot analyses implicated the upregulation of the Mef2c/Egr1 signalling pathway in this neurogenic deficit. Furthermore, miRNA sequencing identified a pronounced decrease in miR-1843a-3p, which was subsequently validated to directly target Mef2c. Collectively, these findings suggest that prenatal gamma irradiation disrupts neurogenic processes and adult brain function, leading to specific behavioral abnormalities. This long-term impairment is associated with, and may be at least partially mediated by, dysregulation of the miR-1843a-3p/Mef2c/Egr1 pathway. Full article

Fragile X Syndrome (FXS) is an inherited cause of intellectual disability and autism, arising from silencing of the Fmr1 gene and loss of Fragile X Messenger Ribonucleoprotein 1 (FMRP). FMRP is an RNA-binding protein critically involved in neurodevelopmental processes, including neurogenesis. We examined the proliferation and maturation of adult-born dentate granule cells (abDGCs) and glial populations in Fmr1 knockout (KO) and wild-type (WT) mice at 4, 12, and 24 weeks of age under control and early-life stress (ELS) conditions. Based on prior findings, we hypothesized that KO mice would exhibit increased neurogenesis and atypical responses to ELS compared with WT mice. Using immunohistochemistry, we quantified multiple stages of neurogenesis in the dentate gyrus, including proliferating (Ki67+), immature (doublecortin [DCX]+), and apoptotic (cleaved caspase-3 [CC3]+) cells. We also assessed glia using Iba1 (microglia) and GFAP (astrocytes) immunoreactivity. KO mice displayed significantly increased Ki67+ proliferating and reduced CC3+ apoptotic cells across ages, accompanied by increased Iba1+ and GFAP+ glial densities. However, KO mice exhibited fewer DCX+ neuroblasts at later time points. When reared in ELS conditions, KO mice show blunted or no changes in neurogenesis and glial populations relative to WT mice reared in ELS conditions or KO mice in control conditions. These results indicate that FMRP loss disrupts hippocampal neurogenesis by increasing cell proliferation while limiting neuronal maturation and expanding glial populations. Moreover, the absence of neurogenic and glial responses to ELS in KO mice highlights a gene–environment interaction that may influence FXS-related neuropathology by limiting the adaptive capacity of the hippocampal neurogenic niche. Full article

Serotonin (5–HT) in the brain is involved in the regulation of various emotional states and behaviors. Most serotonergic neurons are located in the raphe nuclei. The raphe magnus (RMg) is one of the raphe nuclei and belongs to the caudal raphe complex. The primary goal of our research was to examine the effects of chronic, repeated electrical stimulation of the RMg on rats’ motility over a period of 15 days. During the research, 35 rats were used; 21 rats underwent electrical stimulation of the RMg (RMg-ST), while 14 rats were included in the control group (RMg-Sham). In addition, we aimed to evaluate the effects of electrical stimulation in the RMg-ST group as well as the naïve procedure in the RMg-Sham group on anxiety-related behaviors and spatial memory on selected days 30 min after the end of stimulation. We found that rats in the RMg-ST group were characterized by considerably higher locomotor activity than animals in the RMg-Sham group over a 15-day stimulation period. Stimulated animals were less anxious during the elevated plus maze on the 4th and 5th days of stimulation and demonstrated improved memory performance during the Morris water maze conducted between the 9th and 12th days of stimulation in comparison to the control animals. Furthermore, in both behavioral tests, rats’ motility when subjected to the RMg electrical stimulation was much higher than in control rats. On the last day of the 15-day stimulation period, rats were sacrificed, and their brains were collected. Brain immunofluorescent analysis revealed an increase in the number of 5–HT-positive cells in the RMg-ST group and altered activity of c-Fos-positive cells in selected brain structures connected with locomotion (secondary motor cortex), anxiety (arcuate nucleus of the hypothalamus), and spatial memory (dentate gyrus) after stimulation in comparison to the results in the RMg-Sham group. These findings suggest that locomotion may be strictly dependent on the RMg neuronal projections, and electrical stimulation of the structure influences cognitive behaviors. Full article

The Fukushima nuclear accident highlighted that evacuation-related psychosocial harm can outweigh direct radiation risks, underscoring the need to define the health impacts of chronic low-dose-rate (LDR) radiation and evidence-based thresholds for intervention. This study investigated the effects of continuous, postnatal LDR gamma irradiation (1.2 mGy/h, cumulative dose: 5 Gy) in male mice. While no changes in body weight, hippocampal neurogenesis, or major glial and neuronal populations were observed, persistent DNA damage (γ-H2AX foci) in dentate gyrus granule cells occurred in both irradiated male and female mice. Irradiated male mice developed anxiety-like behaviour, a phenotype not observed in a previously published study of female mice subjected to an identical irradiation protocol. Molecular profiling revealed two novel, dysregulated miRNA/mRNA axes in the hippocampus linking DNA damage to behaviour: a maladaptive miR-466i-5p/Tfcp2l1 pathway associated with genomic instability, and a potentially adaptive miR-101a-5p/BMP6 pathway promoting neuronal survival. Venn analysis further identified miR-124b-3p and novel-miR489-3p as conserved exposure biomarkers, altered in both the hippocampus and blood of irradiated animals. Our results show that a high cumulative dose of chronic LDR induces markedly less severe hippocampal pathology than has been reported for equivalent acute doses. These findings support the concept of dose-rate-dependent threshold dose and contribute to the evidence base for developing countermeasures following nuclear incidents or other radiation exposures. Full article

Adult neurogenesis, the process of generating new, functional neurons in the mature central nervous system, represents a key mechanism of brain plasticity and a potential source of regeneration. This process occurs primarily within specialised neurogenic niches: the subgranular zone of the hippocampal dentate gyrus (SGZ) and the subependymal zone (SEZ). It is regulated by a complex network of endogenous factors (e.g., hormones, neurotrophins, growth factors) and exogenous factors (environment, stress, diet, physical activity). Impairments in neurogenesis are linked to the pathogenesis of neurodegenerative diseases, such as Alzheimer’s disease (AD) and Parkinson’s disease (PD). In their course, chronic inflammation, mitochondrial dysfunction, oxidative stress, and the accumulation of pathological proteins (β-amyloid, Tau protein, α-synuclein) create a microenvironment that inhibits the proliferation, differentiation, and survival of new neurons. This results in the exacerbation of cognitive and memory deficits. A review of the literature indicates that modulating neurogenesis through non-pharmacological interventions (e.g., a diet rich in anti-inflammatory compounds, physical exercise) and targeted therapeutic strategies represents a promising, albeit complex, research avenue. The primary challenge remains not only stimulating neuron generation but also ensuring their proper maturation, survival, and functional integration into existing neuronal circuits. A deeper understanding of the molecular and environmental mechanisms regulating adult neurogenesis may open new therapeutic possibilities for slowing the progression of neurodegenerative diseases. Full article

Adult neurogenesis is a regulated form of brain plasticity shaped by interactions between hormonal systems and environmental context. Social experience has been identified as an important modulator of neuronal proliferation, differentiation, and survival across the lifespan, although effects vary across species, developmental stages, and experimental paradigms. This review synthesizes evidence indicating that diverse social behaviors—including isolation, social hierarchy, parenting, sexual interaction, social buffering, and social learning—engage neuroendocrine, neurochemical, and stress-related pathways that are associated with modulation of hippocampal and olfactory neurogenesis. Affiliative and reproductive contexts have been linked in multiple models to enhanced neurogenic indices via gonadal hormones, oxytocinergic and vasopressinergic signaling, and neurotrophic mechanisms, whereas chronic isolation or social defeat has frequently been associated with reduced neurogenic markers, particularly within stress-sensitive regions of the ventral dentate gyrus. Sex differences further shape these patterns, reflecting both biological regulation and uneven sampling across paradigms. Comparative findings in prairie voles, eusocial mole-rats, nonhuman primates, songbirds, and teleost fish indicate that social organization can be accompanied by either increased or constrained neurogenic activity, depending on ecological pressures and life-history strategies. Collectively, the available evidence suggests that adult neurogenesis represents a context-dependent plastic process embedded within vertebrate social systems, while underscoring the need for integrative and evidence-graded interpretations. Full article

Aim: This study investigated the synergistic therapeutic effects and underlying mechanisms of tetrahydroberberine (THB) combined with protopanaxadiol (PPD) on p-chlorophenylalanine (PCPA)-induced insomnia in rats. Methods: Rats were randomly divided into normal, model, diazepam, THB monotherapy, PPD monotherapy, and THB + PPD combination groups. Evaluations included the pentobarbital sleep test, HE staining, ELISA, 16S rRNA sequencing, metabolomics, and Western blot. Results: Results demonstrated that the THB + PPD combination exhibited significant synergistic effects compared with monotherapies: the combination shortened sleep latency by 56.2% (vs. 44.2% for THB alone and 20.7% for PPD alone) and prolonged sleep duration by 112.8% (vs. 70.2% for THB and 59.6% for PPD) relative to the model group, while effectively restoring body weight gain. Histologically, combined treatment significantly alleviated hippocampal neuronal damage and increased the number of intact neurons in the dentate gyrus. Molecularly, it upregulated brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF) levels, restored neurotransmitter balance (serotonin, dopamine, and glutamate), suppressed overactivation of the hypothalamic–pituitary–adrenal (HPA) axis (reducing corticotropin-releasing hormone and corticosterone), and decreased pro-inflammatory cytokine expression. Gut microbiota analysis revealed that the combination restored microbial homeostasis (increasing beneficial bacteria such as *Lactobacillus*) and modulated the glycine–serine–threonine metabolic pathway. Mechanistically, THB + PPD synergistically activated the PI3K/AKT neurotrophic pathway (p-PI3K and p-AKT expression increased by 1.9-fold and 2.5-fold, respectively, vs. model), inhibited the AGE/RAGE pro-inflammatory axis (RAGE expression decreased by 31.8%), and enhanced blood–brain barrier integrity by upregulating tight junction proteins (ZO-1, Occludin). Conclusions: THB combined with PPD exerts synergistic anti-insomnia effects through multi-level regulation of the microbiota–gut–brain axis, neurochemical balance, and key signaling pathways, providing a promising foundation for developing safe natural product-based combination therapies. Full article

Background: After imipenem was introduced in clinical practice, neurologic adverse effects led to recommendations against its use in patients with neurologic conditions. However, these conclusions were drawn without considering pharmacokinetic variations in such patients. Furthermore, animal studies lack the use of clinically relevant doses and supporting morphological studies in both naïve and disease models. Objectives: We aim to study the effects of imipenem in the hippocampus of naïve animals, evaluating potential behavioral and morphological alterations. Methods: Naïve Wistar rats received a 10-day course of intraperitoneal imipenem (40 mg/kg) while controls received a saline injection. After that, they were put through the Morris water maze, elevated plus maze, open-field test, and then euthanized. We analyzed neurogenesis (using doublecortin immunoreactivity), astrogliosis, and the γ-Aminobutyric acid (GABA)ergic system (using parvalbumin (PV), calretinin (CR) and calbindin (CB) immunoreactive (IR) neurons) in the hippocampus. Results: Interestingly, our results showed no significant alterations in both short and long-term memory, nor in anxiety. There were also no significant changes in the neuronal density of doublecortin-immunoreactive (IR) neurons nor in astrogliosis. Furthermore, the areal density of PV- and CR-IR was preserved in all hippocampal subfields. The density of CB-IR neurons also showed no changes in the dentate gyrus, CA3, and subiculum; however, a significant increase was found in the CA1 region. Conclusions: Our results indicate that in naïve individuals, a clinically relevant dose of imipenem does not seem to cause overt behavioral deficits or widespread morphological alterations in the hippocampus. However, a specific increase in the CB-IR neuronal population in the CA1 region highlights a localized cellular alteration/plasticity induced by the imipenem. Hence, pharmacokinetic factors seem to be the potential contributors of imipenem side effects. Further studies should focus on this as a possible cause and focus on individuals with brain diseases. Full article

Mild traumatic brain injury (mTBI) disrupts hippocampal network function through coordinated alterations in glial reactivity, synaptic integrity, and adult neurogenesis. Effective therapeutic approaches targeting these interconnected processes remain limited. Lipid-derived molecules capable of modulating these mTBI-induced disturbances are emerging as promising neuroprotective candidates. Here, we investigated the effects of N-stearidonylethanolamine (SDEA), an ω-3 ethanolamide, in a mouse model of mTBI. SDEA treatment attenuated astrocytic reactivity, restored Arc expression, and improved dendritic spine density and morphology in the CA1 hippocampal area. In the dentate gyrus, mTBI reduced Ki-67-indexed proliferation while leaving DCX-positive immature neurons unchanged, and SDEA partially rescued proliferative activity. These effects were accompanied by improvements in anxiety-like behavior and working-memory performance. Together, these findings demonstrate that SDEA modulates several key components of the glia-synapse-neurogenesis axis and supports functional recovery of hippocampal circuits following mTBI. These results suggest that ω-3 ethanolamides may represent promising candidates for multi-target therapeutic strategies in mTBI. Full article

Post-stress cognitive impairment (PSCI) is defined as a persistent neuropsychiatric condition characterized by deficits in memory consolidation, executive functioning, and environmental interaction following exposure to violent stress. Despite its high incidence, PSCI remains underdiagnosed and lacks effective therapeutic strategies, posing a substantial societal burden and highlighting a critical gap in neuropsychiatric research. A major constraint in mechanistic studies is the persistent reliance on conventional paradigms, notably the Y-maze and novel object recognition test. Their limited sensitivity and poor translational relevance to human cognitive dysfunction, compounded by slow methodological innovation, significantly impede progress. Furthermore, the specific brain regions or neuronal populations contributing to PSCI pathogenesis are insufficiently explored. To address this, we assessed post-stress cognitive impairment in mice using a triple approach: Skinner box assays, traditional behavioral paradigms, and integrated 3D ethological analysis. This multi-method framework provides novel insights for refining animal models and advancing mechanistic understanding. Using c-Fos-based whole-brain screening, we identified the dentate gyrus (DG) as a key region involved in PSCI. Stress caused by violence markedly increased activity in DG CaMKII-expressing neurons. Chemogenetic inhibition of these neurons effectively alleviated stress-induced mild cognitive impairment phenotypes. In summary, by applying novel behavioral assessment tools, this study demonstrates that DG CaMKII neurons play a critical role in regulating post-stress cognitive impairment. Full article

Alzheimer’s disease (AD) is neuropathologically characterized by tau-immunopositive neurofibrillary tangles (NFTs) and amyloid-β (Aβ)-immunopositive senile plaques. According to the widely accepted amyloid cascade hypothesis, Aβ pathology represents the upstream event in AD pathophysiology and induces tau aggregation. However, numerous studies have suggested that tau aggregates correlate more closely with neuronal loss and regional brain atrophy than with Aβ depositions. Tau aggregation in AD demonstrates a hierarchical spreading pattern beginning in the transentorhinal cortex, but the mechanisms underlying this spreading manner of lesions remain to be elucidated. This review aims to address current controversies regarding tau pathology in AD from the perspectives of both the ‘amyloid cascade’ and ‘tauopathy’ hypotheses. From the ‘amyloid cascade’ viewpoint, Aβ deposition prominently involves distal axon and axon terminals, and in some regions, there are anatomical correspondences between axonal Aβ pathology and cytoplasmic tau aggregations (e.g., a close relationship between senile plaques in the molecular layer of the hippocampal dentate gyrus and NFTs in the transentorhinal cortex). Nevertheless, this model cannot explain the whole body of hierarchical spreading of tau aggregation because notable spaciotemporal discrepancies also exist in many regions. From the ‘tauopathy’ perspective, the distribution of tau aggregates in AD involves key nodes within the memory circuits. Also, experimental studies have suggested that patient-derived tau exhibits seeding and neuron-to-neuron propagation properties. Interestingly, tau aggregation in AD appears to spread laterally in a proximity-dependent, cortico-cortical fashion rather than along long-range memory circuits. This contrasts with the system-selective, poly-nodal degenerations seen in four-repeat tauopathies, amyotrophic lateral sclerosis, or spinocerebellar degenerations. Moreover, the proportions of three-repeat and four-repeat isoforms shift during the maturation of NFTs in AD. Overall, spreading patterns of tau-pathology in AD cannot be fully explained by Aβ pathology and also differ from the system degeneration seen in other tauopathies. Full article

Background: Hippocampal neurogenesis in the dentate gyrus persists into adulthood and plays a crucial role in learning and memory. Early-life exposure to low-dose propofol has been reported to enhance neural development in rodent models, but detailed mechanisms remain unclear. To address this gap, we aimed to investigate how low-dose propofol alters neurogenic lineage differentiation, transcriptional programs, and underlying molecular mechanisms within the early postnatal hippocampal neurogenic niche. Results: We conducted an in-depth re-analysis of a published single-nucleus RNA-sequencing (snRNA-seq) dataset from hippocampal tissue of postnatal day 10 (PND10) mice, collected 3 days after low-dose propofol treatment. Uniform Manifold Approximation and Projection (UMAP)-based clustering revealed twelve major cell types, including a population of Ntng1⁺Fxyd7⁺Pcp1⁺ immature pyramidal neurons (imPYR), lacking the mature markers Meis2 and Spock1. Trajectory analysis revealed two neurogenic lineages (granule and pyramidal) and indicated that propofol biases progenitor fate commitment towards the granule lineage. CellChat analysis demonstrated that propofol enhances Neurexin (Nrxn) signaling to neural progenitor cells, suggesting increased synaptic adhesion and maturation. Differential expression analysis (|log₂FC| ≥ 0.26, adjusted p < 0.01) followed by pathway enrichment revealed that propofol upregulates neurogenic maturation pathways—including synaptogenesis, synaptic transmission, dendritic morphogenesis, and memory-related processes—specifically within neural intermediate progenitor cells (nIPC). Conclusions: Together, these findings delineate a coordinated transcriptional and intercellular mechanism by which low-dose propofol reprograms hippocampal neurogenesis during early postnatal development, highlighting progenitor-specific and synapse-oriented processes that may underlie its cognitive-enhancing effects. Full article

Adult neurogenesis is well established in canonical niches—the dentate gyrus and the subventricular zone, where aerobic exercise reliably enhances progenitor proliferation, survival, and synaptic integration via increased cerebral blood flow, neurotrophins (e.g., BDNF, IGF-1), neurotransmitter regulation, and reduced neuroinflammation. Nutraceuticals (e.g., polyphenols, omega-3, creatine, vitamins) further support neuroplasticity and neuronal survival through convergent trophic, anti-inflammatory, and metabolic pathways. By contrast, the hypothalamus, a metabolically pivotal, non-canonical niche, remains comparatively understudied. Here, we synthesize anatomical and functional features of hypothalamic neural stem cells, primarily tanycytes (α1, α2, β1, β2), which line the third ventricle and differentially contribute to neuronal activity regulation, metabolic signaling, and cerebrospinal fluid–portal vasculature coupling, thereby linking neurogenesis to endocrine control. Notably, tanycytes can form neurospheres in vitro, enabling mechanistic interrogation. Although evidence for adult hypothalamic neurogenesis in humans is debated due to methodological constraints, animal data suggest potential relevance to disorders characterized by neuronal loss, metabolic dysregulation, and impaired neuroendocrine function. We propose that an integrative framework is timely: exercise and diet likely interact in the hypothalamic niche through shared mediators (BDNF, IGF-1, CNTF, GPR40) and exercise-derived signals (e.g., lactate, IL-6) that may be complemented by defined nutraceuticals. Yet critical uncertainties persist, including the extent of bona fide hypothalamic neurogenesis, nucleus-specific responses (arcuate nucleus, paraventricular nucleus, ventromedial hypothalamic nucleus), and the mechanistic integration of lifestyle signals in this region. To address these gaps, we outline actionable priorities: (i) single-cell and lineage-tracing studies of tanycyte subtypes under distinct training modalities (aerobic, high-intensity interval training, resistance); (ii) combinatorial interventions pairing structured exercise with nutraceuticals to test synergy on progenitor dynamics and inflammation; and (iii) multi-omics and translational studies to identify biomarkers and establish clinical relevance. Clarifying these interactions will determine whether lifestyle and supplementation strategies can synergistically modulate hypothalamic neurogenesis and inform therapies for neurological, neuropsychiatric, and metabolic disorders. Full article