Search Results (395)

Temporal lobe epilepsy (TLE) is a common drug-resistant epilepsy characterized by recurrent seizures, cognitive impairment, aberrant adult hippocampal neurogenesis, inhibitory circuit disruption, and persistent inflammatory remodeling. Current anti-seizure medications primarily offer symptomatic control and do not target the progressive structural and functional deterioration of epileptic hippocampal networks. Here, we investigated whether local nerve growth factor (NGF)-hydrogel delivery during the latent phase after status epilepticus could mitigate hippocampal pathological remodeling and improve long-term outcomes in a kainic acid (KA)-induced mouse model (utilizing C57BL/6J and Nestin-CreERT2 mice). Animals were randomly assigned to three groups: the saline control group, the untreated KA epilepsy group, and the KA + NGF-hydrogel treatment group. NGF-hydrogel was administered into hippocampal Cornu Ammonis 1 (CA1) beginning 3 days post-kainic acid and repeated every 15 days. Histological, immunofluorescence, circuit-tracing, electrophysiology, electroencephalography (EEG), and behavioral assessments were used to evaluate neurogenesis, microenvironment, circuit readouts, seizure burden, and cognition. NGF-hydrogel treatment was associated with preserved dentate gyrus neural stem cell populations, improved newborn granule cell localization and maturation, attenuated neuroinflammation and gliosis, and partial recovery of inhibitory interneuron markers. These changes were accompanied by improved hippocampal circuit readouts, reduced chronic spontaneous seizure burden, and enhanced recognition and spatial memory. Our findings indicate that local NGF-hydrogel delivery following status epilepticus is associated with improved hippocampal remodeling and functional outcomes, and suggest that biomaterial-based neurotrophic support may be a promising strategy for providing targeted neuroprotection and facilitating excitatory/inhibitory (E/I) balance reconstruction in the epileptic hippocampus. Full article

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

Alzheimer’s disease (AD) is increasingly recognized as a disorder not only of cognition but also of motivation and emotional regulation. Apathy and anhedonia often precede memory deficits, implicating early dysfunction in reward-related circuits. This study investigated whether chronic infusion of palmitoylethanolamide (PEA), a lipid-derived PPARα agonist, could restore motivational behavior and dendritic plasticity in the Tg2576 mouse model of AD. The motivational behavior of mice that received sustained-release PEA pellets for 6 months was assessed by using the conditioned place preference (CPP) paradigm. Morphological and molecular analyses were conducted in the entorhinal cortex (EC), dentate gyrus (DG), and prefrontal cortex (PFC). In Tg2576 mice, PEA significantly rescued CPP performance, increased basal dendritic spines in WT mice in the EC, and both basal and apical dendritic expression in EC and DG from Tg2576 mice, and upregulated the expression of both PPAR-α and brain-derived neurotrophic factor (BDNF) in the PFC. Interestingly, the BDNF increase occurred even in the absence of baseline deficits, suggesting a trophic-enhancement effect. These findings suggest that the PEA-PPARα-BDNF axis may be a potential mechanism for restoring motivation and synaptic integrity in an AD-like mouse model. Lipid-based neuromodulation may therefore offer novel therapeutic routes for addressing non-cognitive symptoms and affective circuitopathy in neurodegenerative diseases. Full article

Chronic stress is among the most pervasive health challenges of contemporary urban life, yet its persistence is not simply a matter of external pressure. When adult hippocampal neurogenesis is impaired, the brain loses its capacity to regulate the hypothalamic–pituitary–adrenal (HPA) axis and distinguish new threats from familiar ones through dentate gyrus pattern separation, rendering stress self-perpetuating. Physical activity is widely recognised as a promoter of neurogenesis through brain-derived neurotrophic factor (BDNF), yet the built environments in which most people spend approximately 90% of their time simultaneously suppress BDNF through chronic stress and deny sufficient physical activity intensity to restore it, a condition known as type 2 allostatic overload sustained by architectural impoverishment. This paper proposes architectural enrichment as a theoretical framework designed to resolve this problem at its root through two independent but synergistic mechanisms: architecturally mediated voluntary stair use to elevate peripheral BDNF via metabolic pathways, and neurobiophilic design based on the Neurobiophilia Index to attenuate cortisol and passively support BDNF and neurogenesis. Twelve hypothesised neurobiological profiles are derived in a framework that advances the concept of hippocampal neurosustainability, proposing that buildings can be designed not merely to avoid harming the brain but to actively sustain its capacity for resilience amid the stressors of modern urban living. Full article

A reliable isolation of the dentate gyrus (DG) is a critical pre-analytical step for region-specific neurobiological assays, yet DG microdissection practices vary widely and are rarely compared quantitatively under standardized conditions. In addition, long-term paraformaldehyde-fixed archival brain tissue is commonly regarded as unsuitable for microdissection because of reduced pliability and poor anatomical contrast, limiting its use for training and protocol development. Here, we quantitatively compare two commonly used DG microdissection strategies, a medial (intact-block) approach and a coronal (slice-guided) approach across fresh, fixed, and softened-fixed rat brain hemispheres under matched conditions. To enable the use of archival material, fixed hemispheres were subjected to a simple 15-day slow-running tap water softening protocol to improve tissue handling and landmark visibility. Dissection duration and anatomical specificity were evaluated, the latter quantified by measuring residual cornu ammonis (CA)1–3 area on hematoxylin–eosin-stained coronal sections following DG removal. In fresh tissue, the medial approach enabled significantly faster DG isolation than the coronal approach, while both strategies achieved comparable anatomical specificity. In softened-fixed tissue, dissection times increased for both approaches, but the same relative performance ranking was preserved. Softening markedly improved tissue pliability and boundary visualization, particularly benefiting the coronal, stepwise dissection strategy. Residual CA1–3 areas did not differ significantly between approaches or tissue states. This study provides a validated, training-oriented DG microdissection workflow that supports methodological standardization, reproducibility, and 3R-aligned use of archival tissue, strengthening the pre-analytical foundation for downstream region-specific neuroscience assays. 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

Extensive research in laboratory rodents has shown that novelty exposure enhances the consolidation of memories for preceding or following low-arousal events by elevating dopamine release in the dorsal hippocampus (dHipp). Additionally, numerous studies have demonstrated that post-encoding noradrenergic activation of the basolateral amygdala (BLA) can also enhance memory consolidation in dHipp. Since the BLA is most active during emotionally arousing or stress-related situations, it was suggested that this nuclear complex mediates the effects of emotional salience on memory consolidation. However, it is presently unknown whether the reinforcement of memory storage in dHipp induced by novel and arousing environmental conditions results from the interaction between these two modulatory systems. To test the hypothesis of a functional interaction between dopaminergic and noradrenergic systems, this study assessed their combined effects on a low-arousal object-location (OL) task. Rats received post-training intra-BLA infusions of vehicle or clenbuterol (Clen), a selective β-adrenoceptor agonist. Novelty-induced dopamine release in the dHipp was enhanced by omitting habituation prior to training, and the contribution of dopamine signaling was further evaluated using pre-infusion administration of the D1/D5 receptor antagonist SCH 23390. The distribution of two important proteins for memory processing, namely the activity-regulated cytoskeleton-associated protein (Arc) and the phosphorylated form of the transcription factor, cAMP-response element-binding protein (pCREB) in the dHipp, was explored in a subset of rats perfused 60 min after the training phase. Stimulation of the BLA significantly increased the number of Arc- and pCREB-positive cells in several dHipp areas. The preceding application of SCH 23390, however, substantially decreased these effects in the same areas, i.e., the dentate gyrus (DG), CA2, and CA1 subregions for pCREB, and the CA3b, CA3c, CA2, and CA1 subregions for Arc. This interaction is considered essential for the initial stages of memory consolidation. The obtained results indicate the presence of a region-specific interaction between BLA modulatory inputs and intrahippocampal dopaminergic transmission, the mechanisms of which remain to be elucidated. Full article