Current Opinion on the Use of c-Fos in Neuroscience

Chronic social stress induces generalized hyper-sensitivity to aversion: A mouse model with translational validity for understanding and treating negative valence disorders

The RDoC framework focuses on neurobehavioral processes often dysfunctional in mental disorders and commensurate with translational research. Generalized hyper-sensitivity to aversion/threat is common in various stress-related emotional disorders; increased Pavlovian aversion learning-memory (PAL, PAM) provides a translational paradigm for its study. Here we present the development and application of a mouse model for the study of generalized hyper-sensitivity to aversion/threat. In male adult mice, chronic exposure to social aversion (chronic social stress, CSS) leads, relative to controls (CON), to increased acquisition and expression of tone-footshock conditioned freezing behavior. The altered neurobehavioral state of CSS mice is expected to involve structure-function changes in amygdala: in CSS mice, higher levels of both PAL and PAM freezing behavior co-occurred with fewer lateral/basal amygdala glutamate neurons expressing the immediate early-gene protein c-Fos. A current antidepressant, SSRI escitalopram, reversed excessive PAM freezing behavior in CSS mice with sub-chronic dosing. The model was applied to investigate 3 compounds with novel mechanisms of action: indoleamine dioxygenase 1 (IDO 1) inhibition, somatostatin receptor 4 (SSTR4) agonism, and transient receptor potential canonical channels 4 and 5 (TRPC4/5) inhibition. For each, there was evidence for attenuation of excessive PAL and/or PAM in CSS mice. Preclinical validation of TRPC4/5 channels inhibition contributed to the decision to investigate, and accurately predicted, clinical efficacy, measured as reduced amygdala and emotional reactivities to aversion in major depressive disorder. Future work will focus on (back-)translational studies that address stress-induced changes in amygdala reactivity and aversion processing, their underlying etio-pathophysiological causes, and neuropharmacological responsiveness.

Inhibition of Endoplasmic Reticulum Oxidoreductin 1 Modulates Neuronal Excitability and Nociceptive Sensitivity in Mice

BACKGROUND

In the peripheral nervous system, nociceptors become hyperexcitable in both acute and chronic pain conditions. This phenotype can be mediated by dysregulated calcium, which occurs if the endoplasmic reticulum and mitochondria fail to buffer it appropriately. The redox enzyme endoplasmic reticulum oxidoreductin 1 (ERO1) regulates calcium transfer at endoplasmic reticulum-mitochondria contact sites (ERMCSs). This study hypothesized that inhibiting ERO1 and thereby dampening ERMCS calcium transfer might lower nociceptor hyperexcitability in sensory neurons and pain-like behaviors in mice.

METHODS

C57BL/6 mice were used for histology, behavior, and cell culture experiments. Behavior included thermal tail flick, the formalin hind paw injection model of acute inflammatory pain, and hind paw incision postsurgical pain. Postmortem human dorsal root ganglia (DRGs) were used for immunohistochemistry and in vitro calcium imaging.

RESULTS

This study demonstrates that the α isoform of ERO1 is expressed in mouse DRGs across multiple subtypes of mouse sensory neurons. This led us to peripherally administer an ERO1 inhibitor in mice, which acutely reversed nociception in acute inflammatory and postsurgical pain models. The hypothesis was that this may be due to reduced excitability of DRG neurons and tested ERO1 inhibition in vitro. In cultured DRGs, ERO1 inhibition dampened nociceptor excitability and mitochondrial function, suggesting that reduced calcium transfer through ERMCS could be responsible for the behavior observed in vivo . ERO1α expression was also found in human DRGs using immunohistochemistry and previously published single-cell RNA-sequencing data. Finally, the study showed that ERO1 inhibition modulates human sensory neuronal excitability in cultured post-mortem DRGs.

CONCLUSIONS

This study found that ERO1 inhibition dampens mitochondrial function, sensory neuron excitability, and acute pain-like behavior in mice. Additionally, ERO1 inhibition decreases sensory neuron excitability in post-mortem human sensory neurons in vitro. The results indicate that targeting ERO1 may be a viable strategy for non-narcotic acute pain relief.

Modulation of dorsal raphe nucleus connectivity and serotonergic signalling to the insular cortex in the prosocial effects of chronic fluoxetine

Long-term exposure to fluoxetine and other selective serotonin reuptake inhibitors alters social and anxiety-related behaviours, including social withdrawal, which is a symptom of several neuropsychiatric disorders. Adaptive changes in serotonergic neurotransmission likely mediate this delayed effect, although the exact mechanisms are still unclear. Here we investigated the functional circuitry underlying the biphasic effects of fluoxetine on social approach-avoidance behaviour and explored the place of serotonergic dorsal raphe nucleus (DR) ensembles in this network, using c-Fos-immunoreactivity as a correlate of activity. Graph theory-based network analysis revealed changes in patterns of functional connectivity and identified neuronal populations in the insular cortex (IC) and serotonergic populations in the DR as central targets to the prosocial effects of chronic fluoxetine. To determine the role of serotonergic projections to the IC, a retrograde tracer was micro-injected in the IC prior to fluoxetine treatment and social behaviour testing. Chronic fluoxetine increased c-Fos immunoreactivity in insula-projecting neurons of the rostral, ventral part of the DR (DRV). Using a virally delivered Tet-Off platform for temporally-controlled marking of neuronal activation, we observed that chronic fluoxetine may affect social behaviour by influencing independent but interconnected populations of serotonergic DR ensembles. These findings suggest that sustained fluoxetine exposure causes adaptive changes in functional connectivity due to altered serotonergic neurotransmission in DR projection targets, and the increased serotonergic signalling to the IC likely mediates some of the therapeutic effects of fluoxetine on social behaviour.

Brain activation following flexible stimulation paradigms of transcorneal electrical stimulation (TES) in a murine model of glaucoma

Transcorneal electrical stimulation (TES) has been shown as a promising treatment for optic neuropathy in DBA/2J glaucoma model mice, however the current knowledge about the most effective application parameters, such as intensity and duration, is limited. In this study, after electrophysiological evaluation and intraocular pressure measurements, a single TES treatment in both eyes was performed and expression of c-Fos in the superior colliculus measured as a response. Groups were formed with 4, 8-month-old mice, 2 male and 2 female, and treated with 1, 10, or 100 μA for 10 or 30 min; a group with no stimulation was used as negative control, and as positive control, a group of mice were injected intraperitoneally with saline solution. As pathophysiology baseline, groups of 3-month-old mice were used to compare the c-Fos expression after injection (positive control), and with no stimulation (negative controls). The 8-month-old mice presented measurable progression of neuropathy compared to young controls. Active c-Fos-labeled cells were detected with TES application as low as 1 μA for 30 min, suggesting that benefits of TES can be harnessed with flexible application paradigms.

Sex-specific effects of chronic fluoxetine on c-Fos expression in Murine brain regions

Fluoxetine (FLX), a selective serotonin reuptake inhibitor, is widely prescribed for treating mood disorders. Despite its therapeutic benefits, the precise mechanisms and brain regions impacted by long-term FLX treatment remain understood. To explore this, we analyzed c-Fos immunoreactivity in brain regions associated with emotional regulation after 30-day oral FLX treatment in male and female mice. Our findings showed a significant reduction in c-Fos expression in FLX-treated groups compared to controls, suggesting decreased cellular activity in several brain regions. Furthermore, significant sex differences were observed as male mice exhibited higher c-Fos activity than females. Treatment interaction indicated FLX might reduce these sex disparities, except in the CA2 region of the hippocampus, where males maintained higher activity. Notably, FLX appeared to minimize the sex-based disparities in c-Fos expression in several regions, suggesting that FLX equalizes cellular activity across sexes in areas associated with cognitive and emotional functions. Altogether, these data indicate that FLX modulates cellular activity via a sex-dependent mechanism, which highlights the relevance of considering sex differences in the assessment of the neurobiological effects of FLX.

Seizure Circuit Activity in the Theiler's Murine Encephalomyelitis Virus Model of Infection-induced Epilepsy Using Transient Recombination in Active Populations

Epilepsy affects one in twenty-six individuals. A major cause of epilepsy worldwide is viral encephalitis. Central nervous system infections can provoke seizures in the short term and increase the risk of spontaneous, recurrent seizures post-infection. However, the neural mechanisms underlying seizures during acute infection are unknown. These neuronal changes can be studied in C57BL6/J mice infected with Theiler's murine encephalomyelitis virus (TMEV). TMEV-infected mice experience seizures 3-8 days post-injection (DPI), clear the virus by DPI 14, and may develop chronic, acquired temporal lobe epilepsy. TMEV may incite seizures during the acute infection period through inflammation, reactive gliosis, and cell death in hippocampal area CA1. Here, we explore the neuronal circuits underlying acute seizures in TMEV-injected mice using c-Fos driven TRAP (targeted recombination in active populations). TRAP mice (c-Fos- CreERT2 x CAG-tdTomato) were injected with PBS or TMEV and gently handled on DPI 5 to induce seizures. 4-OHT was administered to mice either 1.5 or 3 hr after seizures to tag the active cells expressing c-Fos with tdTomato. After 1 week, the mice were sacrificed and whole mouse brains were sectioned and immunostained for tdTomato expression. Percent area of fluorescence was quantified, and comparisons were made between TMEV-injected mice and PBS controls, sites ipsilateral vs contralateral to TMEV injection site, and between sexes. TdTomato expression was elevated in the TMEV-injected mice in the ipsilateral and contralateral hippocampus, thalamus, lateral septal nucleus, basal ganglia, triangular septal nucleus, fornix, and corpus callosum. Critically, the expression pattern suggests that seizures induced on DPI 5 arise from the hilus, dentate gyrus, and CA3 hippocampal subregions. Generalized seizures during acute TMEV infection may have propagated to the contralateral hemisphere via CA3 and the hippocampal commissure. TRAP has not been previously utilized in the TMEV mouse model and these experiments address crucial questions regarding seizure spread during TMEV infection.

GRAPHICAL ABSTRACT

Temporal interference stimulation over the motor cortex enhances cortical excitability in rats

Temporal Interference Stimulation (TIS) represents a novel non-invasive brain stimulation technique that deeply targets specific brain regions using the differential beat frequency of two high-frequency stimulation pairs. This study investigated the neuromodulatory effects of TIS at different beat frequencies on cortical excitability in the rat motor cortex. Rats were randomly assigned into four groups, receiving TIS at alpha (10 Hz), beta (20 Hz), gamma (70 Hz), or sham frequencies targeting the motor cortex for 20 min under anesthesia. Cortical excitability and inhibition were evaluated by measuring motor-evoked potentials (MEPs), input-output (I/O) curves, and long-interval intracortical inhibition (LICI) before and after TIS. Additionally, immunohistochemistry was performed for neural biomarkers c-Fos and glutamic acid decarboxylase (GAD-65) to confirm targeted neural activation following TIS. We also examined glial fibrillary acidic protein (GFAP)-positive cells in the stimulated region to assess astrocyte responses associated with TIS. Alpha and gamma TIS significantly increased MEP amplitudes compared to sham stimulation. The analysis of I/O curves revealed a significant enhancement in the area under the curve (AUC) post-stimulation in the alpha and gamma TIS groups. Notably, only gamma TIS significantly reduced intracortical inhibition, indicated by an increased LICI ratio post-stimulation. Immunohistochemical analysis demonstrated a significant 35% increase in c-Fos-positive cells in the stimulated motor cortex regions after TIS compared to sham, whereas no significant changes in GAD-65-positive cells or GFAP expression were observed. These findings indicate that a single session of alpha or gamma TIS effectively modulates cortical excitability, highlighting its potential for targeted neuromodulation applications.

Early life social complexity shapes adult neural processing in the communal spiny mouse Acomys cahirinus

RATIONALE

Early life social rearing has profound consequences on offspring behavior and resilience. Yet, most studies examining early life development in rodents use species whose young are born immobile and do not produce complex social behavior until later in development. Furthermore, models of rearing under increased social complexity, rather than deprivation, are needed to provide alternative insight into the development of social neural circuitry.

OBJECTIVES

To understand precocial offspring social development, we manipulated early life social complexity in the communal spiny mouse Acomys cahirinus and assessed long-term consequences on offspring social behavior, exploration, and neural responses to novel social stimuli.

METHODS

Spiny mouse pups were raised in the presence or absence of a non-kin breeding group. Upon adulthood, subjects underwent social interaction tests, an open field test, and a novel object test. Subjects were then exposed to a novel conspecific and novel group and neural responses were quantified via immunohistochemical staining in brain regions associated with social behavior.

RESULTS

Early life social experience did not influence behavior in the test battery, but it did influence social processing. In animals exposed to non-kin during development, adult lateral septal neural responses toward a novel conspecific were weaker and hypothalamic neural responses toward a mixed-sex group were stronger.

CONCLUSIONS

Communal species may exhibit robust behavioral resilience to the early life social environment. But the early life environment can affect how novel social information is processed in the brain during adulthood, with long-term consequences that are likely to shape their behavioral trajectory.

Effects of two different peptides on pentylenetetrazole-induced seizures in larval zebrafish

Epilepsy is a common and severe neurological disease characterized by spontaneous and recurrent seizures. Although anti-seizure treatments are effective for most patients, approximately 30% remain pharmacoresistant. Moreover, uncontrolled seizures are associated with increased health risks and shortened life expectancy in individuals with refractory epilepsy. Preclinical studies play a crucial role in drug discovery, and the zebrafish (Danio rerio) have been successfully employed for this purpose. In this study, we utilized the zebrafish PTZ-induced seizure model to evaluate the effects of two peptides on seizure responses: Tripeptide (p-BTX-I) and the CX2 (a Cx43derivated peptide). Zebrafish larvae at 6 days post-fertilization were pre-treated with these peptides at various concentrations, depending on their experimental groups, 24h prior to seizure induction. We assessed seizure frequency, quantified swimming activity, measured transcript levels of genes related to inflammation and apoptosis (il1b, tnfa, cox1, cox2a, il6, casp3a, casp9, baxa, bcl2a, and c-fos), and analyzed the biodistribution of both peptides. Our results indicate that the Tripeptide exhibited anti-inflammatory and anti-apoptotic effects, particularly through reducing the expression of il1b and casp9. CX2 pre-treatment significantly downregulated inflammatory markers (il1b, il6, tnfa, and cox1). Biodistribution analysis confirmed that the CX2 peptide reached the zebrafish brain, suggesting a direct role in modulating seizure-related pathways. Our findings demonstrate that Tripeptide and CX2 peptides can modulate gene expression and mitigate molecular response associated with epileptic seizures in the zebrafish brain. These peptides thus represent promising candidates for future research aimed at developing novel anti-epileptic therapies. However, additional studies are required to evaluate their long-term efficacy, elucidate underlying mechanisms of action, and explore potential translational applications.

Neuroprotective potential of hispidulin and diosmin: a review of molecular mechanisms

Flavonoids are an important class of natural products, particularly, belong to a class of plant secondary metabolites having a polyphenolic structure. They are widely found in fruits, vegetables, and certain beverages. Hispidulin and diosmin are naturally occurring flavonoids recognized for their potential health benefits, such as antioxidant, anti-inflammatory, and neuroprotective properties. Hispidulin is present in several plants, including Arnica montana, Salvia officinalis (sage), and Eupatorium arnottianum. Diosmin is mainly extracted from citrus fruits like lemons and oranges and can also be synthesized from hesperidin, another flavonoid found in citrus fruits. Neurodegenerative diseases are characterized by complex signaling pathways that contribute to neuronal deterioration. The JAK/STAT pathway is involved in inflammatory responses, while the NF-κB/NLRP3 pathway is associated with metabolic stress and inflammation, both facilitating neurodegeneration. Conversely, the AMPK/pGSK3β pathway is crucial for neuroprotection, regulating cellular responses to oxidative stress and promoting neuronal survival. Additionally, the BACE/Aβ pathway exacerbates neuronal damage by triggering inflammatory and oxidative stress responses, highlighting critical targets for therapeutic strategies. Hispidulin and diosmin have emerged as promising agents in the modulation of mediators involved in neuroinflammation and neurodegenerative diseases. Oxidative stress and inflammatory pathways, including those driven by Aβ/BACE1 and JAK/STAT signaling, are central to neuronal damage and disease progression. Recent studies highlight that hispidulin and diosmin exhibit notable neuroprotective effects by targeting these mediators. Hispidulin has been shown to impact key inflammatory cytokines and adhesion molecules, while diosmin influences proinflammatory cytokine production and inflammasome activation. Both compounds offer potential therapeutic benefits by modulating crucial mediators linked to neuroinflammation and neurodegeneration. This review article is designed to explore the intricate mechanistic interplay underlying the neuroprotective effects of hispidulin and diosmin.

HSP70 Modulators for the Correction of Cognitive, Mnemonic, and Behavioral Disorders After Prenatal Hypoxia

Background/Objectives: Prenatal hypoxia (PH) is a leading cause of nervous system disorders in early childhood and subsequently leads to a decline in the cognitive and mnemonic functions of the central nervous system (such as memory impairment, reduced learning ability, and information processing). It also increases anxiety and the risk of brain disorders in adulthood. Compensatory-adaptive mechanisms of the mother-placenta-fetus system, which enhance the fetus's CNS resilience, are known, including the activation of endogenous neuroprotection in response to hypoxic brain injury through the pharmacological modulation of HSP70. Methods: To evaluate the effect of HSP70 modulators-Cerebrocurin, Angiolin, Tamoxifen, Glutaredoxin, Thiotriazoline, and HSF-1 (heat shock factor 1 protein), as well as Mildronate and Mexidol-on the motor skills, exploratory behaviors, psycho-emotional activities, learning, and memories of offspring after PH. Experimental PH was induced by daily intraperitoneal injections of sodium nitrite solution into pregnant female rats from the 16th to the 21st day of pregnancy at a dose of 50 mg/kg. The newborns received intraperitoneal injections of Angiolin (50 mg/kg), Thiotriazoline (50 mg/kg), Mexidol (100 mg/kg), Cerebrocurin (150 µL/kg), L-arginine (200 mg/kg), Glutaredoxin (200 µg/kg), HSF-1 (50 mg/kg), or Mildronate (50 mg/kg) for 30 days. At 1 month, the rats were tested in the open field test, and at 2 months, they were trained and tested for working and spatial memory in the radial maze. Results: Modeling PH led to persistent impairments in exploratory activity, psycho-emotional behavior, and a decrease in the cognitive-mnestic functions of the CNS. It was found that Angiolin and Cerebrocurin had the most pronounced effects on the indicators of exploratory activity and psycho-emotional status in 1-month-old animals after PH. They also exhibited the most significant cognitive-enhancing and memory-supporting effects during the training and evaluation of skill retention in the maze in 2-month-old offspring after PH. Conclusions: for the first time, we obtained experimental data on the effects of HSP70 modulators on exploratory activity, psycho-emotional behavior, and cognitive-mnestic functions of the central nervous system in offspring following intrauterine hypoxia. Based on the results of this study, we identified the pharmacological agents Angiolin and Cerebrocurin as promising neuroprotective agents after perinatal hypoxia.

Deletion of Fgf14 confers resilience to basal and stress-induced depressive-like behavior and reduces anxiety in mice

Depression is a mental illness characterized by despair behavior, inability to feel pleasure, and social withdrawal. Causes are not yet clarified, but stress is a condition that induces depression. Neuronal alterations, comprising maladaptive neuronal plasticity and excitability, are present in both responses to stress and depression. Fibroblast growth factor 14 (Fgf14) controls neuronal excitability and proper action potential firing by stabilizing voltage-dependent sodium (Nav) channels into the axon. Fgf14-Nav channels complex is regulated by glycogen synthase kinase 3. Recently, Fgf14 has been genetically associated to depression. However, little is known about its role in controlling stress-induced depression. This study demonstrates that female Fgf14-/- mice are resilient to depression, as reported by reduced level of despair behavior, anhedonia, and increased sociability. Also, a reduction of anxious-like behavior was highlighted. Fgf14-/- mice showed increased expression of cannabinoid receptor without alterations of dopaminergic system in mPFC, suggesting a link between Fgf14 and endocannabinoid system in the control mechanisms underlying depression. Neuronal activity was assessed by analyzing cFOS expression during basal and following acute stress induced by tail suspension test (TST). The analysis revealed that neuronal activation in mPFC and VTA was correlated to immobility, where ratio of cFOS expression over immobility was significantly higher in Fgf14-/- mice. This suggests that higher neuronal activity might be involved in resilience to depression. In resilient Fgf14-/- mice, TST-induced acute stress caused activation only in pyramidal neurons. Our findings suggest that Fgf14 is involved in stress-coping mechanisms and could be targeted to improve resilience to depression.

Effects of Integrated Extracts of Trigonella foenum-graecum and Asparagus racemosus on Hot Flash-like Symptoms in Ovariectomized Rats

Vasomotor symptoms, such as hot flashes (HFs), commonly affect women during menopause, leading to a reduced quality of life. The current study evaluates the combined effect of active components Asparagus racemosus (AR) and Trigonella foenum-graecum (TFG) in a single oral formulation (IAT) for alleviating menopausal symptoms in ovariectomized rats. Following bilateral ovariectomy, the animals were randomly assigned to nine groups: (1) Control, (2) Ovariectomy (OVX), (3) OVX+TA1 (TA: Combination of Trigonella and Asparagus; TFG 30 mg/kg + AR 30 mg/kg), (4) OVX+TA2 (TFG 30 mg/kg + AR 15 mg/kg), (5) OVX+TA3 (TFG 15 mg/kg + AR 30 mg/kg), (6) OVX+TA4 (TFG 40 mg/kg + AR 30 mg/kg), (7) OVX+TA5 (TFG 30 mg/kg + AR 40 mg/kg), (8) OVX+IAT1 (IAT: Integrated Asparagus and Trigonella; TFG+AR integrated extract, 30 mg/kg), and (9) OVX+IAT2 (TFG+AR integrated extract, 60 mg/kg). On the 8th day of treatment, tail and skin temperatures were recorded every 30 min for 24 h. Ovariectomized rats exhibited menopausal symptoms, such as hormonal imbalances and elevated skin temperature. Administration of AR, TFG, and IAT significantly decreased serum follicle-stimulating hormone (FSH), luteinizing hormone (LH), and cortisol while increasing estradiol, progesterone, and dopamine (p < 0.0001), effectively alleviating hot flash-like symptoms. Additionally, they mitigated ovariectomy-induced oxidative stress by lowering malondialdehyde (MDA) levels and restoring antioxidant enzyme activity. Ovariectomized rats exhibited increased expression of a proto-oncogene (c-FOS), gonadotropin-releasing hormone (GnRH), Kisspeptin, Neurokinin B (NKB), and Transient receptor potential vanilloid 1 (TRPV1), along with reduced expressing brain-derived neurotrophic factor (BDNF) levels, which were reversed by treatment, especially with the IAT2 combination. The AR and TFG combination, particularly in IAT formulations, showed strong potential in alleviating menopausal symptoms in ovariectomized rats. These findings suggest that the combination of AR and TFG extracts could be a natural alternative for managing postmenopausal symptoms by restoring reproductive hormone levels, regulating lipid profiles, and enhancing antioxidant defense systems.

Proteomic Investigation of Neurotrophic trans-Banglene Reveals Potential Link to Iron Homeostasis

In an effort to gain insight into cellular systems impacted by neurotrophic trans-banglene (t-BG), global proteomic profiling and Western blot analyses were employed. Expression level changes in response to t-BG treatment were compared to those observed with nerve growth factor (NGF), a natural neurotrophic protein and functional analog to t-BG. Findings from these studies did not point to direct interception of NGF/TrkA signaling by t-BG. Instead, significant alterations in iron-binding and iron-regulating proteins were observed. While total iron levels showed no change across all treatments, intracellular iron measurements and mitochondrial iron measurements demonstrated lower ferrous (Fe2+) ion levels in t-BG treated cells but not in NGF treated cells. These results highlight a potential connection between iron regulation and neurotrophic activity, a relationship which has, to date, not been well studied. These results are also notable given that iron dysregulation occurs in most neurodegenerative disease settings, and that iron has been shown to facilitate protein aggregation and apoptotic mechanisms.

Possible brain regions involved in parturition in mice

Parturition is a vital physiological process in the reproduction of female mammals, regulated by neurohumoral mechanisms coordinated by the central nervous system. The uterus is essential for this process; however, the neural pathways connecting the brain to the uterus remain poorly understood. In this study, we combined the pseudorabies virus (PRV) tracing tool with c-Fos immunofluorescence staining to identify brain regions that may regulate uterine muscle activity during parturition. We observed that the paraventricular nucleus (PVN), periaqueductal gray (PAG), and locus coeruleus (LC) were colabeled with PRV and c-Fos. Subsequently, we focused on the PVN to determine whether its activity correlated with parturition behavior. We used fiber photometry to record Ca2+ activity in the PVN during parturition in freely behaving mice and found a strong correlation between PVN activity and parturition behavior. Our results demonstrate that this method is both accessible and reliable for studying the roles of central-peripheral neural pathways involved in parturition behavior and suggest that PVN may be a key brain node for parturition.NEW & NOTEWORTHY Parturition is a vital physiological process in the reproduction of female mammals. Here, the authors established a method that combined retrograde tracing, c-Fos immunofluorescence staining, and fiber photometry to study the roles of central-peripheral neural pathways involved in parturition. Our method is simple and reliable to investigate the roles of central-peripheral neural pathways involved in a range of physiological processes in freely moving animals.

Developmental changes in brain-wide fear memory networks

Memory retrieval involves coordinated activity across multiple brain regions. Yet how the organization of memory networks evolves throughout development remains poorly understood. In this study, we compared whole-brain functional networks that are active during contextual fear memory recall in infant, juvenile, and adult mice. Our analyses revealed that long-term memory networks change significantly across postnatal development. Infant fear memory networks are dense and heterogeneous, whereas adult networks are sparse and have a small-world topology. While hippocampal subregions were highly connected nodes at all ages, the cortex gained many functional connections across development. Different functional connections matured at different rates, but their developmental timing fell into three major categories: stepwise change between two ages, linear change across all ages, or inverted-U, with elevated functional connectivity in juveniles. Our work highlights how a subset of brain regions likely maintain important roles in fear memory encoding, but the functional connectivity of fear memory networks undergoes significant reorganization across development. Together, these results provide a blueprint for studying how correlated cellular activity in key areas distinctly regulates memory storage and retrieval across development.

The cortical areas processing periodontal ligament nociception in mice

OBJECTIVES

Toothaches are often poorly localized. Although periodontal pain is better localized, it can spread to other areas. Ultimately, the cerebral cortex processes nociception, with somatotopic organization possibly playing a role in localizing the origin. However, the exact cortical area in the periodontal ligament (PDL) remains unclear.

METHODS

This study examined cortical responses to electrical stimulation of the molar PDL in anesthetized male mice using in vivo optical imaging with a voltage-sensitive dye, autofluorescent flavin fluorescence, and immunohistochemistry for c-Fos protein expression.

RESULTS

On optical imaging, cortical responses to the stimulation of the ipsilateral and contralateral PDL of the upper and lower teeth were observed in the primary somatosensory cortex (S1) and area from the insular cortex (IC) to the ventral edge of the secondary somatosensory cortex (S2), defined as the area caudal to the middle cerebral artery (C-area). Responses in S1 were faint and unstable, but were consistent in the C-area. The initial response locations were similar regardless of which PDL was stimulated, and the activated areas in the C-area almost overlapped. Three-dimensional construction of c-Fos-immunopositive cells responding to upper or lower PDL stimulation revealed bilateral distribution in the cingulate gyrus, secondary auditory cortex, temporal association cortex, ectorhinal cortex, and IC, but not in the S1 and S2.

CONCLUSION

These results suggest that the somatotopic organization of the S1, S2, and IC cannot explain the localization of PDL nociception. The predominance of responses in the contralateral IC may provide clues for identifying the laterality.

Loss of Endothelial TRPC1 Induces Aortic Hypercontractility and Hypertension

BACKGROUND

The increasing prevalence of obesity-related cardiovascular diseases demands a better understanding of the contribution of different cell types to vascular function for developing new treatment strategies. Previous studies have established a fundamental role of TRPC1 (transient receptor potential channel canonical family member 1) in blood vessels. However, little is known about its functional roles within different cell types.

METHODS

We generated endothelial-specific TRPC1-deficient and knockin mice and analyzed their changes in vascular function under physiological and pathologically obese state. Wire myography, Ca2+ image, blood pressure measurements, RNA-sequencing analysis, liquid chromatography-mass spectrometry, immunoblotting, ELISA, luciferase reporter assay, and morphometric assessments were performed to unravel phenotype and molecular changes in response to the absence or presence of endothelial TRPC1.

RESULTS

Loss of endothelial TRPC1 reduced endothelial-dependent relaxation and exaggerated endothelial-dependent contraction in mouse aorta. As expected, loss of endothelial TRPC1 amplified blood pressure and decreased acetylcholine-induced intracellular Ca2+ concentration rise in the aorta. In endothelial-specific TRPC1-deficient mouse arteries, the mRNA profile identified upregulation of c-Fos (Fos proto-oncogene, activator protein-1 transcription factor subunit). Blockade of c-Fos rescued the impaired vasomotor tone in the aorta of mice deficient in endothelial TRPC1. Endothelial TRPC1-regulated nitric oxide/endothelin-1 production is involved in vascular c-Fos expression. Moreover, knockin of endothelial TRPC1 ameliorated enhanced endothelial-dependent contraction and hypertension in obese mice which is related to alleviated endothelial endothelin-1/c-Fos production and smooth muscle contraction.

CONCLUSIONS

Our results identify endothelial TRPC1 as a previously unclear regulator of vascular changes and blood pressure in both physiological and pathologically obese state, and it is associated with nitric oxide/endothelin-1/c-Fos signaling.

Trajectories of working memory and decision making abilities along juvenile development in mice

Rodents commonly serve as model organisms for the investigation of human mental disorders by capitalizing on behavioral commonalities. However, our understanding of the developmental dynamics of complex cognitive abilities in rodents remains incomplete. In this study, we examined spatial working memory as well as odor-and texture-based decision making in mice using a delayed non-match to sample task and a two-choice set-shifting task, respectively. Mice were investigated during different stages of development: pre-juvenile, juvenile, and young adult age. We show that, while working memory abilities in mice improve with age, decision making performance peaks during juvenile age by showing a sex-independent trajectory. Moreover, cFos expression, as a first proxy for neuronal activity, shows distinct age-and brain area-specific changes that relate to task-specific behavioral performance. The distinct developmental trajectories of working memory and decision making in rodents resemble those previously reported for humans.

Regulatory Elements for Gene Therapy of Epilepsy

The problem of drug resistance in epilepsy means that in many cases, a surgical treatment may be advised. But this is only possible if there is an epileptic focus, and resective brain surgery may have adverse side effects. One of the promising alternatives is gene therapy, which allows the targeted expression of therapeutic genes in different brain regions, and even in specific cell types. In this review, we provide detailed explanations of some key terms related to genetic engineering, and describe various regulatory elements that have already been used in the development of different approaches to treating epilepsy using viral vectors. We compare a few universal promoters for their strength and duration of transgene expression, and in our description of cell-specific promoters, we focus on elements driving expression in glutamatergic neurons, GABAergic neurons and astrocytes. We also explore enhancers and some other cis-regulatory elements currently used in viral vectors for gene therapy, and consider future perspectives of state-of-the-art technologies for designing new, stronger and more specific regulatory elements. Gene therapy has multiple advantages and should become more common in the future, but there is still a lot to study and invent in this field.

Integration of Glucagon-Like Peptide 1 Receptor Actions Through the Central Amygdala

Understanding the detailed mechanism of action of glucagon-like peptide 1 receptor (GLP-1R) agonists on distinct topographic and genetically defined brain circuits is critical for improving the efficacy and mitigating adverse side effects of these compounds. In this mini-review, we propose that the central nucleus of the amygdala (CeA) is a critical mediator of GLP-1R agonist-driven hypophagia. Here, we review the extant literature demonstrating CeA activation via GLP-1R agonists across multiple species and through multiple routes of administration. The precise role of GLP-1Rs within the CeA is unclear but the site-specific GLP-1Rs may mediate distinct behavioral and physiological hallmarks of GLP-1R agonists on food intake. Thus, we propose important novel directions and methods to test the role of the CeA in mediating GLP-1R actions.

Macrophage-induced enteric neurodegeneration leads to motility impairment during gut inflammation

Current studies pictured the enteric nervous system and macrophages as modulators of neuroimmune processes in the inflamed gut. Expanding this view, we investigated the impact of enteric neuron-macrophage interactions on postoperative trauma and subsequent motility disturbances, i.e., postoperative ileus. In the early postsurgical phase, we detected strong neuronal activation, followed by transcriptional and translational signatures indicating neuronal death and synaptic damage. Simultaneously, our study revealed neurodegenerative profiles in macrophage-specific transcriptomes after postoperative trauma. Validating the role of resident and monocyte-derived macrophages, we depleted macrophages by CSF-1R-antibodies and used CCR2-/- mice, known for reduced monocyte infiltration, in POI studies. Only CSF-1R-antibody-treated animals showed decreased neuronal death and lessened synaptic decay, emphasizing the significance of resident macrophages. In human gut samples taken early and late during abdominal surgery, we substantiated the mouse model data and found reactive and apoptotic neurons and dysregulation in synaptic genes, indicating a species' overarching mechanism. Our study demonstrates that surgical trauma activates enteric neurons and induces neurodegeneration, mediated by resident macrophages, introducing neuroprotection as an option for faster recovery after surgery.

Brain Plasticity and Cell Competition: Immediate Early Genes Are the Focus

Brain plasticity is at the basis of many cognitive functions, including learning and memory. It includes several mechanisms of synaptic and extrasynaptic changes, neurogenesis, and the formation and elimination of synapses. The plasticity of synaptic transmission involves the expression of immediate early genes (IEGs) that regulate neuronal activity, thereby supporting learning and memory. In addition, IEGs are involved in the regulation of brain cells' metabolism, proliferation, and survival, in the establishment of multicellular ensembles, and, presumably, in cell competition in the tissue. In this review, we analyze the current understanding of the role of IEGs (c-Fos, c-Myc, Arg3.1/Arc) in controlling brain plasticity in physiological and pathological conditions, including brain aging and neurodegeneration. This work might inspire new gene therapy strategies targeting IEGs to regulate synaptic plasticity, and potentially prevent or mitigate neurodegenerative diseases.

Expression of c-fos in cortical neuron cultures under dynamic magnetic field is not suppressed by calcium channel blockers

Previously, we developed a dynamic magnetic field (DMF) device using neodymium magnets that induced c-fos expression in cortical neurons, while activity-regulated cytoskeleton-associated protein (Arc), and brain-derived neurotrophic factor (BDNF) remained unaffected. The precise signal transduction pathway for c-fos induction under DMF was unclear. This study aimed to investigate the mechanism of immediate early gene (IEG) induction using calcium channel blockers (CCBs). Six experiments were conducted with cortical neurons, employing an NMDA receptor antagonist and an L-type voltage-dependent calcium channel blocker as CCBs. Neuronal cultures were exposed to DMF, CCBs, or both, and IEG expression (Arc, c-fos, BDNF) was measured through polymerase chain reaction. Results showed a tendency for increased c-fos expression with DMF exposure, which was unaffected by CCBs. In contrast, Arc and BDNF were not induced under DMF exposure but were significantly inhibited by CCBs. These findings suggest that c-fos induction under DMF involves a distinct pathway, potentially relevant to stress resistance and drug discovery.

Water deprivation induces a systemic procatabolic state that differentially affects oxidative and glycolytic skeletal muscles in male mice

Dehydration, characterized by the loss of total body water and/or electrolytes due to diseases or inadequate fluid intake, is prevalent globally but often underestimated. Its contribution to long-term chronic diseases and sarcopenia is recognized, yet the mechanisms involved in systemic and muscle protein metabolism during dehydration remain unclear. This study investigated metabolic adaptations in a 36-h water deprivation (WD) model of mice. Male C57BL/6 mice underwent 36-h WD or pair-feeding at rest, with assessments of motor skills along with biochemical and metabolic parameters. Dehydration was confirmed by hypernatremia, body mass loss, hyporexia, and increased activity of vasopressinergic and oxytocinergic neurons compared with controls. These results were associated with liver mass loss, decreased glycemia, and increased cholesterolemia. In addition, increased V̇o2 and a decreased respiratory exchange ratio indicated reduced carbohydrate consumption and potentially increased protein use during dehydration. Thus, skeletal muscle protein metabolism was evaluated due to its high protein content. In the oxidative muscles of the WD group, total and proteasomal proteolysis increased, which was associated with decreased Akt-mediated intracellular signaling. Interestingly, there was an increase in fiber cross-sectional area, likely due to higher muscle water content caused by increased intracellular osmolality induced by protein catabolism products. Conversely, no changes were observed in protein turnover or water content in glycolytic muscles. These findings suggest that short-term WD imposes a procatabolic state, depleting protein content in skeletal muscle. However, skeletal muscle may respond differently to dehydration based on its phenotype and might adapt for a limited time.NEW & NOTEWORTHY This study investigated the effects of WD on mouse homeostasis, focusing on energy substrates and skeletal muscle protein metabolism. Our findings revealed a shift toward reduced dependence on carbohydrate degradation and increased reliance on lipid oxidation, or even protein oxidation, as energy sources, since we observed increased proteolysis in one muscle phenotype. Despite body mass loss, soleus and EDL muscle masses were differently affected. These results indicate the procatabolic potential of short-term WD in mice.

Development of an rpS6-Based Ex Vivo Assay for the Analysis of Neuronal Activity in Mouse and Human Olfactory Systems

Olfactory sensitivity to odorant molecules is a complex biological function influenced by both endogenous factors, such as genetic background and physiological state, and exogenous factors, such as environmental conditions. In animals, this vital ability is mediated by olfactory sensory neurons (OSNs), which are distributed across several specialized olfactory subsystems depending on the species. Using the phosphorylation of the ribosomal protein S6 (rpS6) in OSNs following sensory stimulation, we developed an ex vivo assay allowing the simultaneous conditioning and odorant stimulation of different mouse olfactory subsystems, including the main olfactory epithelium, the vomeronasal organ, and the Grueneberg ganglion. This approach enabled us to observe odorant-induced neuronal activity within the different olfactory subsystems and to demonstrate the impact of environmental conditioning, such as temperature variations, on olfactory sensitivity, specifically in the Grueneberg ganglion. We further applied our rpS6-based assay to the human olfactory system and demonstrated its feasibility. Our findings show that analyzing rpS6 signal intensity is a robust and highly reproducible indicator of neuronal activity across various olfactory systems, while avoiding stress and some experimental limitations associated with in vivo exposure. The potential extension of this assay to other conditioning paradigms and olfactory systems, as well as its application to other animal species, including human olfactory diagnostics, is also discussed.

Mapping of c-Fos Expression in Rat Brain Sub/Regions Following Chronic Social Isolation: Effective Treatments of Olanzapine, Clozapine or Fluoxetine

The c-Fos as a marker of cell activation is used to identify brain regions involved in stimuli processing. This review summarizes a pattern of c-Fos immunoreactivity and the overlapping brain sub/regions which may provide hints for the identification of neural circuits that underlie depressive- and anxiety-like behaviors of adult male rats following three and six weeks of chronic social isolation (CSIS), relative to controls, as well as the antipsychotic-like effects of olanzapine (Olz), and clozapine (Clz), and the antidepressant-like effect of fluoxetine (Flx) in CSIS relative to CSIS alone. Additionally, drug-treated controls relative to control rats were also characterized. The overlapping rat brain sub/regions with increased expression of c-Fos immunoreactivity following three or six weeks of CSIS were the retrosplenial granular cortex, c subregion, retrosplenial dysgranular cortex, dorsal dentate gyrus, paraventricular nucleus of the thalamus (posterior part, PVP), lateral/basolateral (LA/BL) complex of the amygdala, caudate putamen, and nucleus accumbens shell. Increased activity of the nucleus accumbens core following exposure of CSIS rats either to Olz, Clz, and Flx treatments was found, whereas these treatments in controls activated the LA/BL complex of the amygdala and PVP. We also outline sub/regions that might represent potential neuroanatomical targets for the aforementioned antipsychotics or antidepressant treatments.

Butin Protects Keratinocytes From Particulate Matter 2.5 and Ultraviolet B-Mediated Damages

BACKGROUND

Butin is a naturally occurring compound with a wide range of medicinal properties, including anti-inflammatory, anti-arthritic, and antioxidant properties. Particulate matter 2.5 (PM2.5) and ultraviolet B (UVB) radiation contribute to skin cell damage via the induction of oxidative stress.

METHODS

This study sought to assess the protective effects of butin against damage triggered by PM2.5 and UVB in human HaCaT keratinocytes. Assessments were performed to evaluate cell viability, apoptosis, and cellular component damage.

RESULTS

Butin exhibited its protective ability via the inhibition of PM2.5-induced reactive oxygen species generation, lipid peroxidation, DNA damage, protein carbonylation, and mitochondrial damage. Butin reduced the PM2.5-induced c-Fos and phospho-c-Jun protein levels as well as mitogen-activated protein kinase. Furthermore, butin mitigated PM2.5- and UVB-induced apoptosis.

CONCLUSION

Butin had the potential as a pharmaceutical candidate for treating skin damage caused by PM2.5 and UVB exposure.

Frustrative Nonreward: Behavior, Circuits, Neurochemistry, and Disorders

The surprising omission or reduction of vital resources (food, fluid, social partners) can induce an aversive emotion known as frustrative nonreward (FNR), which can influence subsequent behavior and physiology. FNR is an integral mediator of irritability/aggression, motivation (substance use disorders, depression), anxiety/fear/threat, learning/conditioning, and social behavior. Despite substantial progress in the study of FNR during the twentieth century, research lagged in the later part of the century and into the early twenty-first century until the National Institute of Mental Health's Research Domain Criteria initiative included FNR and loss as components of the negative valence domain. This led to a renaissance of new research and paradigms relevant to basic and clinical science alike. The COVID-19 pandemic's extensive individual and social restrictions were correlated with increased drug and alcohol use, social conflict, irritability, and suicide, all potential consequences of FNR. This article highlights animal models related to these psychiatric disorders and symptoms and presents recent advances in identifying the brain regions and neurotransmitters implicated.

A review of possible biomarkers for opioid tolerance

Knowledge of opioid tolerance in a deceased person is important for distinguishing between therapeutic and toxic opioid concentrations for that particular individual when interpreting postmortem toxicological results. However, no biomarkers for opioid tolerance are currently available. This review aimed to study the existing literature on mechanisms or changes in signaling pathways related to chronic opioid use, which could be relevant for further studies to identify biomarkers for opioid tolerance. We performed a systematic literature search using the PRISMA 2020 guidelines using the MeSH terms "opioid tolerance AND biomarkers" in PubMed, Embase, WebofScience, and the Cochrane library. A review of the search results yielded seven studies on animal models or humans, identifying and evaluating thirteen possible biomarkers in terms of specificity for changes induced by opioids and other aspects to be considered as potential biomarkers. We evaluated nine potential biomarkers as unlikely to be specific for opioid tolerance, and one had contradictory results in terms of upregulation or downregulation. However, methylation of the promoter region of the μ-opioid receptor gene, increased activity of soluble puromycin-sensitive aminopeptidase, altered miRNA profile, or other multiple component profiling may be interesting to study further as biomarkers for opioid tolerance in forensic postmortem cases.

Effects of Head-Only Exposure to 900 MHz GSM Electromagnetic Fields in Rats: Changes in Neuronal Activity as Revealed by c-Fos Imaging without Concomitant Cognitive Impairments

Over the last two decades, animal models have been used to evaluate the physiological and cognitive effects of mobile phone exposure. Here, we used a head-only exposure system in rats to determine whether exposure to 900 MHz GSM electromagnetic fields (EMFs) induces regional changes in neuronal activation as revealed by c-Fos imaging. In a first study, rats were exposed for 2 h to brain average specific absorption rates (BASARs) ranging from 0.5 to 6 W/kg. Changes in neuronal activation were found to be dose-dependent, with significant increases in c-Fos expression occurring at BASAR of 1 W/kg in prelimbic, infralimbic, frontal, and cingulate cortices. In a second study, rats were submitted to either a spatial working memory (WM) task in a radial maze or a spatial reference memory (RM) task in an open field arena. Exposures (45 min) were conducted before each daily training session (BASARs of 1 and 3.5 W/kg). Control groups included sham-exposed and control cage animals. In both tasks, behavioral performance evolved similarly in the four groups over testing days. However, c-Fos staining was significantly reduced in cortical areas (prelimbic, infralimbic, frontal, cingulate, and visual cortices) and in the hippocampus of animals engaged in the WM task (BASARs of 1 and 3.5 W/kg). In the RM task, EMF exposure-induced decreases were limited to temporal and visual cortices (BASAR of 1 W/kg). These results demonstrate that both acute and subchronic exposures to 900 MHz EMFs can produce region-specific changes in brain activity patterns, which are, however, insufficient to induce detectable cognitive deficits in the behavioral paradigms used here.

Exploring the globoid cell leukodystrophy protein network and therapeutic interventions

Globoid cell leukodystrophy is a severe rare disorder characterized by white matter degradation, resulting in a progressive loss of physical and mental abilities and has extremely limited therapeutic interventions. Therefore, this study aimed to delve into the Globoid cell leukodystrophy associated intricate network of differentially expressed genes (p < 0.05, |Fc|> 1) to identify potential druggable targets and possible therapeutic interventions using small molecules. The disease-associated neuronal protein circuit was constructed and analyzed, identifying 53 nodes (minimum edge cutoff 1), among which five (FOS, FOSB, GDNF, GFRA1, and JUN) were discerned as potential core protein nodes. Although our research enumerates the potential small molecules to target various protein nodes in the proposed disease network, we particularly underscore T-5224 to inhibit c-Jun activity as JUN was identified as one of the pivotal elements within the disease-associated neuronal protein circuit. The evaluation of T-5224 binding energy (- 11.0 kcal/mol) from docking study revealed that the compound to exhibit a notable affinity towards Jun/CRE complex. Moreover, the structural integrity of complex was affirmed through comprehensive molecular dynamics simulations, indicating a stable hydrophilic interaction between T-5224 and the Jun/CRE complex, thereby enhancing protein compactness and reducing solvent accessibility. This binding energy was further substantiated by free binding analysis, revealing a substantial thermodynamics complex state (- 448.00 ± 41.73 kJ/mol). Given that this investigation is confined to a computational framework, we additionally propose a hypothetical framework to ascertain the feasibility of inhibiting the Jun/CRE complex with T-5224 against Globoid cell leukodystrophy, employing a combination of in vitro and in vivo methodologies as a prospective avenue of this study.

scL-2PAM: A Novel Countermeasure That Ameliorates Neuroinflammation and Neuronal Losses in Mice Exposed to an Anticholinesterase Organophosphate

Due to their inhibition of acetylcholinesterase, organophosphates are among the most toxic of chemicals. Pralidoxime (a.k.a 2-PAM) is the only acetylcholinesterase reactivator approved in the U.S., but 2-PAM only poorly traverses the blood-brain barrier. Previously, we have demonstrated that scL-2PAM, a nanoformulation designed to enter the brain via receptor-mediated transcytosis, is superior to unencapsulated 2-PAM for reactivating brain acetylcholinesterase, ameliorating cholinergic crisis, and improving survival rates for paraoxon-exposed mice. Here, we employ histology and transcriptome analyses to assess the ability of scL-2PAM to prevent neurological sequelae including microglial activation, expression of inflammatory cytokines, and ultimately loss of neurons in mice surviving paraoxon exposures. Levels of the mRNA encoding chemokine ligand 2 (CCL2) were significantly upregulated after paraoxon exposures, with CCL2 mRNA levels in the brain correlating well with the intensity and duration of cholinergic symptoms. Our nanoformulation of 2-PAM was found to be superior to unencapsulated 2-PAM in reducing the levels of the CCL2 transcript. Moreover, brain histology revealed that scL-2PAM was more effective than unencapsulated 2-PAM in preventing microglial activation and the subsequent loss of neurons. Thus, scL-2PAM appears to be a new and improved countermeasure for reducing neuroinflammation and mitigating brain damage in survivors of organophosphate exposures.

The differential effects of blocking retinal orexin receptors on the expression of retinal c-fos and hypothalamic Vip, PACAP, Bmal1, and c-fos in Male Wistar Rats

Orexin A and B (OXA and OXB) and their receptors are expressed in the majority of retinal neurons in humans, rats, and mice. Orexins modulate signal transmission between the different layers of the retina. The suprachiasmatic nucleus (SCN) and the retina are central and peripheral components of the body's biological clocks; respectively. The SCN receives photic information from the retina through the retinohypothalamic tract (RHT) to synchronize bodily functions with environmental changes. In present study, we aimed to investigate the impact of inhibiting retinal orexin receptors on the expression of retinal Bmal1 and c-fos, as well as hypothalamic c-fos, Bmal1, Vip, and PACAP at four different time-points (Zeitgeber time; ZT 3, 6, 11, and ZT-0). The intravitreal injection (IVI) of OX1R antagonist (SB-334867) and OX2R antagonist (JNJ-10397049) significantly up-regulated c-fos expression in the retina. Additionally, compared to the control group, the combined injection of SB-334867 and JNJ-10397049 showed a greater increase in retinal expression of this gene. Moreover, the expression of hypothalamic Vip and PACAP was significantly up-regulated in both the SB-334867 and JNJ-10397049 groups. In contrast, the expression of Bmal1 was down-regulated. Furthermore, the expression of hypothalamic c-fos was down-regulated in all groups treated with SB-334867 and JNJ-10397049. Additionally, the study demonstrated that blocking these receptors in the retina resulted in alterations in circadian rhythm parameters such as mesor, amplitude, and acrophase. Finally, it affected the phase of gene expression rhythms in both the retina and hypothalamus, as identified through cosinor analysis and the zero-amplitude test. This study represents the initial exploration of how retinal orexin receptors influence expression of rhythmic genes in the retina and hypothalamus. These findings could provide new insights into how the retina regulates the circadian rhythm in both regions and illuminate the role of the orexinergic system expression within the retina.

c-fos induction in the choroid plexus, tanycytes and pars tuberalis is an early indicator of spontaneous arousal from torpor in a deep hibernator

Hibernation is an extreme state of seasonal energy conservation, reducing metabolic rate to as little as 1% of the active state. During the hibernation season, many species of hibernating mammals cycle repeatedly between the active (aroused) and hibernating (torpid) states (T-A cycling), using brown adipose tissue (BAT) to drive cyclical rewarming. The regulatory mechanisms controlling this process remain undefined but are presumed to involve thermoregulatory centres in the hypothalamus. Here, we used the golden hamster (Mesocricetus auratus), and high-resolution monitoring of BAT, core body temperature and ventilation rate, to sample at precisely defined phases of the T-A cycle. Using c-fos as a marker of cellular activity, we show that although the dorsomedial hypothalamus is active during torpor entry, neither it nor the pre-optic area shows any significant changes during the earliest stages of spontaneous arousal. Contrastingly, in three non-neuronal sites previously linked to control of metabolic physiology over seasonal and daily time scales - the choroid plexus, pars tuberalis and third ventricle tanycytes - peak c-fos expression is seen at arousal initiation. We suggest that through their sensitivity to factors in the blood or cerebrospinal fluid, these sites may mediate metabolic feedback-based initiation of the spontaneous arousal process.

Central amygdala is related to the reduction of aggressive behavior by monosodium glutamate ingestion during the period of development in an ADHD model rat

Introduction

Monosodium glutamate (MSG), an umami substance, stimulates the gut-brain axis communication via gut umami receptors and the subsequent vagus nerves. However, the brain mechanism underlying the effect of MSG ingestion during the developmental period on aggression has not yet been clarified. We first tried to establish new experimental conditions to be more appropriate for detailed analysis of the brain, and then investigated the effects of MSG ingestion on aggressive behavior during the developmental stage of an ADHD rat model.

Methods

Long-Evans, WKY/Izm, SHR/Izm, and SHR-SP/Ezo were individually housed from postnatal day 25 for 5 weeks. Post-weaning social isolation (PWSI) was given to escalate aggressive behavior. The resident-intruder test, that is conducted during the subjective night, was used for a detailed analysis of aggression, including the frequency, duration, and latency of anogenital sniffing, aggressive grooming, and attack behavior. Immunohistochemistry of c-Fos expression was conducted in all strains to predict potential aggression-related brain areas. Finally, the most aggressive strain, SHR/Izm, a known model of attention-deficit hyperactivity disorder (ADHD), was used to investigate the effect of MSG ingestion (60 mM solution) on aggression, followed by c-Fos immunostaining in aggression-related areas. Bilateral subdiaphragmatic vagotomy was performed to verify the importance of gut-brain interactions in the effect of MSG.

Results

The resident intruder test revealed that SHR/Izm rats were the most aggressive among the four strains for all aggression parameters tested. SHR/Izm rats also showed the highest number of c-Fos + cells in aggression-related brain areas, including the central amygdala (CeA). MSG ingestion significantly decreased the frequency and duration of aggressive grooming and attack behavior and increased the latency of attack behavior. Furthermore, MSG administration successfully increased c-Fos positive cell number in the intermediate nucleus of the solitary tract (iNTS), a terminal of the gastrointestinal sensory afferent fiber of the vagus nerve, and modulated c-Fos positive cells in the CeA. Interestingly, vagotomy diminished the MSG effects on aggression and c-Fos expression in the iNTS and CeA.

Conclusion

MSG ingestion decreased PWSI-induced aggression in SHR/Izm, which was mediated by the vagus nerve related to the stimulation of iNTS and modulation of CeA activity.

Distinct subpopulations of ventral pallidal cholinergic projection neurons encode valence of olfactory stimuli

To better understand the function of cholinergic projection neurons in the ventral pallidum (VP), we examined behavioral responses to appetitive (APP) and aversive (AV) odors that elicited approach or avoidance, respectively. Exposure to each odor increased cFos expression and calcium signaling in VP cholinergic neurons. Activity and Cre-dependent viral vectors selectively labeled VP cholinergic neurons that were activated and reactivated in response to either APP or AV odors, but not both, identifying two non-overlapping populations of VP cholinergic neurons differentially activated by the valence of olfactory stimuli. These two subpopulations showed differences in electrophysiological properties, morphology, and projections to the basolateral amygdala. Although VP neurons are engaged in both approach and avoidance behavioral responses, cholinergic signaling is only required for approach behavior. Thus, two distinct subpopulations of VP cholinergic neurons differentially encode valence of olfactory stimuli and play distinct roles in approach and avoidance behaviors.

Exercise induction at expression immediate early gene (c-Fos, ARC, EGR-1) in the hippocampus: a systematic review

The immediate early gene exhibits activation markers in the nervous system consisting of ARC, EGR-1, and c-Fos and is related to synaptic plasticity, especially in the hippocampus. Immediate early gene expression is affected by physical exercise, which induces direct ARC, EGR-1, and c-Fos expression.

Objective

To assess the impact of exercise, we conducted a literature study to determine the expression levels of immediate early genes (ARC, c-Fos, and EGR-1).

Methods

The databases accessed for online literature included PubMed-Medline, Scopus, and ScienceDirect. The original English articles were selected using the following keywords in the title: (Exercise OR physical activity) AND (c-Fos) AND (Hippocampus), (Exercise OR physical activity) AND (ARC) AND (Hippocampus), (Exercise OR physical activity) AND (EGR-1 OR zif268) AND (Hippocampus).

Results

Physical exercise can affect the expression of EGR-1, c-Fos, and ARC in the hippocampus, an important part of the brain involved in learning and memory. High-intensity physical exercise can increase c-Fos expression, indicating neural activation. Furthermore, the expression of the ARC gene also increases due to physical exercise. ARC is a gene that plays a role in synaptic plasticity and regulation of learning and memory, changes in synaptic structure and increased synaptic connections, while EGR-1 also plays a role in synaptic plasticity, a genetic change that affects learning and memory. Overall, exercise or regular physical exercise can increase the expression of ARC, c-Fos, and EGR-1 in the hippocampus. This reflects the changes in neuroplasticity and synaptic plasticity that occur in response to physical activity. These changes can improve cognitive function, learning, and memory.

Conclusion

c-Fos, EGR-1, and ARC expression increases in hippocampal neurons after exercise, enhancing synaptic plasticity and neurogenesis associated with learning and memory.

Activation of lateral preoptic neurons is associated with nest-building in male mice

Nest-building behavior is a widely observed innate behavior. A nest provides animals with a secure environment for parenting, sleep, feeding, reproduction, and temperature maintenance. Since animal infants spend their time in a nest, nest-building behavior has been generally studied as parental behaviors, and the medial preoptic area (MPOA) neurons are known to be involved in parental nest-building. However, nest-building of singly housed male mice has been less examined. Here we show that male mice spent longer time in nest-building at the early to middle dark phase and at the end of the dark phase. These two periods are followed by sleep-rich periods. When a nest was removed and fresh nest material was introduced, both male and female mice built nests at Zeitgeber time (ZT) 6, but not at ZT12. Using Fos-immunostaining combined with double in situ hybridization of Vgat and Vglut2, we found that Vgat- and Vglut2-positive cells of the lateral preoptic area (LPOA) were the only hypothalamic neuron population that exhibited a greater number of activated cells in response to fresh nest material at ZT6, compared to being naturally awake at ZT12. Fos-positive LPOA neurons were negative for estrogen receptor 1 (Esr1). Both Vgat-positive and Vglut2-positive neurons in both the LPOA and MPOA were activated at pup retrieval by male mice. Our findings suggest the possibility that GABAergic and glutamatergic neurons in the LPOA are associated with nest-building behavior in male mice.

Essential role of ROS - 8-Nitro-cGMP signaling in long-term memory of motor learning and cerebellar synaptic plasticity

Although reactive oxygen species (ROS) are known to have harmful effects in organisms, recent studies have demonstrated expression of ROS synthases at various parts of the organisms and the controlled ROS generation, suggesting possible involvement of ROS signaling in physiological events of individuals. However, physiological roles of ROS in the CNS, including functional roles in higher brain functions or neuronal activity-dependent ROS production, remain to be elucidated. Here, we demonstrated involvement of ROS - 8-NO2-cGMP signaling in motor learning and synaptic plasticity in the cerebellum. In the presence of inhibitors of ROS signal or ROS synthases, cerebellar motor learning was impaired, and the stimulus inducing long-term depression (LTD), cellular basis for the motor learning, failed to induce LTD but induced long-term potentiation (LTP)-like change at cerebellar synapses. Furthermore, ROS was produced by LTD-inducing stimulus in enzyme-dependent manner, and excess administration of the antioxidant vitamin E impaired cerebellar motor learning, suggesting beneficial roles of endogenous ROS in the learning. As a downstream signal, involvement of 8-NO2-cGMP in motor learning and cerebellar LTD were also revealed. These findings indicate that ROS - 8-NO2-cGMP signal is activated by neuronal activity and is essential for cerebellum-dependent motor learning and synaptic plasticity, demonstrating involvement of the signal in physiological function of brain systems.

Cellular and molecular mechanisms involved in the analgesic effects of botulinum neurotoxin: A literature review

Botulinum neurotoxins (BoNTs), derived from Clostridium botulinum, have been employed to treat a range of central and peripheral neurological disease. Some studies indicate that BoNT may be beneficial for pain conditions as well. It has been hypothesized that BoNTs may exert their analgesic effects by preventing the release of pain-related neurotransmitters and neuroinflammatory agents from sensory nerve endings, suppressing glial activation, and inhibiting the transmission of pain-related receptors to the neuronal cell membrane. In addition, there is evidence to suggest that the central analgesic effects of BoNTs are mediated through their retrograde axonal transport. The purpose of this review is to summarize the experimental evidence of the analgesic functions of BoNTs and discuss the cellular and molecular mechanisms by which they can act on pain conditions. Most of the studies reviewed in this article were conducted using BoNT/A. The PubMed database was searched from 1995 to December 2022 to identify relevant literature.

Forskolin rescues hypoxia-induced cognitive dysfunction in zebrafish with potential involvement of O-GlcNAc cycling regulation

Repeated sublethal hypoxia exposure induces brain inflammation and affects the initiation and progression of cognitive dysfunction. Experiments from the current study showed that hypoxic exposure downregulates PKA/CREB signaling, which is restored by forskolin (FSK), an adenylate cyclase activator, in both Neuro2a (N2a) cells and zebrafish brain. FSK significantly protected N2a cells from hypoxia-induced cell death and neurite shrinkage. Intraperitoneal administration of FSK for 5 days on zebrafish additionally led to significant recovery from hypoxia-induced social interaction impairment and learning and memory (L/M) deficit. FSK suppressed hypoxia-induced neuroinflammation, as indicated by the observed decrease in NF-κB activation and GFAP expression. We further investigated the potential effect of FSK on O-GlcNAcylation changes induced by hypoxia. Intriguingly FSK induced marked upregulation of the protein level of O-GlcNAc transferase catalyzing addition of the GlcNAc group to target proteins, accompanied by elevated O-GlcNAcylation of nucleocytoplasmic proteins. The hypoxia-induced O-GlcNAcylation decrease in the brain of zebrafish was considerably restored following FSK treatment. Based on the collective results, we propose that FSK rescues hypoxia-induced cognitive dysfunction, potentially through regulation of HBP/O-GlcNAc cycling.

Age-related decline in social interaction is associated with decreased c-Fos induction in select brain regions independent of oxytocin receptor expression profiles

Social behavior decreases with aging, and we have previously found a substantial decline in social investigative behavior of old female rats. In this study we examined the neural activation pattern (c-Fos mRNA) of young (3 month) and old (18 month) female rats after brief 10 min exposure to a novel female rat in order to identify forebrain regions that show selective age-related alterations in their neural response to social investigation. We also measured relative oxytocin receptor expression (Oxtr mRNA) as a possible factor in age-related declines in c-Fos induction after social interaction. Young rats exposed to a social partner had a greater c-Fos mRNA response than those exposed to novel context alone in the lateral septum and septohypothalamic area, with blunted increases evident in old rats. In addition, c-Fos mRNA levels in the lateral septum were positively correlated with social investigative behavior. Interestingly, age-related differences in c-Fos gene induction were unrelated to the local amount of Oxtr expression within specific brain regions, although we found an age-related decline in Oxtr expression in the ventromedial hypothalamus. This functional neuroanatomical characterization may point to certain brain regions that are especially sensitive to age-related declines associated with social interaction behavior.

Repetitive spreading depolarization induces gene expression changes related to synaptic plasticity and neuroprotective pathways

Spreading depolarization (SD) is a slowly propagating wave of profound depolarization that sweeps through cortical tissue. While much emphasis has been placed on the damaging consequences of SD, there is uncertainty surrounding the potential activation of beneficial pathways such as cell survival and plasticity. The present study used unbiased assessments of gene expression to evaluate that compensatory and repair mechanisms could be recruited following SD, regardless of the induction method, which prior to this work had not been assessed. We also tested assumptions of appropriate controls and the spatial extent of expression changes that are important for in vivo SD models. SD clusters were induced with either KCl focal application or optogenetic stimulation in healthy mice. Cortical RNA was extracted and sequenced to identify differentially expressed genes (DEGs). SDs using both induction methods significantly upregulated 16 genes (vs. sham animals) that included the cell proliferation-related genes FOS, JUN, and DUSP6, the plasticity-related genes ARC and HOMER1, and the inflammation-related genes PTGS2, EGR2, and NR4A1. The contralateral hemisphere is commonly used as control tissue for DEG studies, but its activity could be modified by near-global disruption of activity in the adjacent brain. We found 21 upregulated genes when comparing SD-involved cortex vs. tissue from the contralateral hemisphere of the same animals. Interestingly, there was almost complete overlap (21/16) with the DEGs identified using sham controls. Neuronal activity also differs in SD initiation zones, where sustained global depolarization is required to initiate propagating events. We found that gene expression varied as a function of the distance from the SD initiation site, with greater expression differences observed in regions further away. Functional and pathway enrichment analyses identified axonogenesis, branching, neuritogenesis, and dendritic growth as significantly enriched in overlapping DEGs. Increased expression of SD-induced genes was also associated with predicted inhibition of pathways associated with cell death, and apoptosis. These results identify novel biological pathways that could be involved in plasticity and/or circuit modification in brain tissue impacted by SD. These results also identify novel functional targets that could be tested to determine potential roles in the recovery and survival of peri-infarct tissues.

Temporal pattern of Fos and Jun families expression after mitogenic stimulation with FGF-2 in rat neural stem cells and fibroblasts

Intense stimulation of most living cells triggers the activation of immediate early genes, such as Fos and Jun families. These genes are important in cellular and biochemical processes, such as mitosis and cell death. The present study focused on determining the temporal expression pattern of Fos and Jun families in fibroblasts and neural stem cells of cerebellum, hippocampus, and subventricular zone (SVZ) of rats of different ages at 0, 0.5, 1, 3, and 6 h after stimulation with fibroblast growth factor (FGF)-2. In neonates, a similar expression pattern was observed in all cells analyzed, with lower expression in basal condition, peak expression at 0.5 h after stimulation, returning to baseline values between 1 and 3 h after stimulation. On the other hand, cells from adult animals only showed Fra1 and JunD expression after stimulation. In fibroblasts and hippocampus, Fra1 reached peak expression at 0.5 h after stimulation, while in the SVZ, peak level was observed at 6 h after stimulation. JunD in fibroblasts presented two peak expressions, at 0.5 and 6 h after stimulation. Between these periods, the expression observed was at a basal level. Nevertheless, JunD expression in SVZ and hippocampus was low and without significant changes after stimulation. Differences in mRNA expression in neonate and adult animals characterize the significant differences in neurogenesis and cell response to stimulation at different stages of development. Characterizing these differences might be important for the development of cell cultures, replacement therapy, and the understanding of the physiological response profile of different cell types.

High dose administration of DREADD agonist JHU37160 produces increases in anxiety-like behavior in male rats

Designer receptors exclusively activated by designer drugs (DREADDs) are a promising tool for analyzing neural circuitry, and improved DREADD-selective ligands continue to be developed. Relative to clozapine-N-oxide (CNO), JHU37160 is a selective DREADD agonist recently shown to exhibit higher blood brain barrier penetrance and DREADD selectivity in vivo; however, relatively few studies have characterized the behavioral effects of systemic JHU37160 administration in animals. Here, we report a dose-dependent anxiogenic effect of systemic JHU37160 in male Wistar and Long-Evans rats, regardless of DREADD expression, with no impact on locomotor behavior. These results suggest that high dose (1 mg/kg) JHU37160 should be avoided when performing chemogenetic experiments designed to evaluate circuit manipulation on anxiety-like behavior in rats.

Intermittent Exposure to a Single Bottle of Ethanol Modulates Stress Sensitivity: Impact of Age at Exposure Initiation

Alcohol use during adolescence is a serious public health problem, with binge drinking and high-intensity drinking being particularly harmful to the developing adolescent brain. To investigate the adverse consequences of binge drinking and high-intensity adolescent drinking, adolescent rodents were intermittently exposed to ethanol through intragastric gavage, intraperitoneal injection, or vapor inhalation. These models revealed the long-lasting behavioral and neural consequences of adolescent intermittent ethanol (AIE) exposure. The present study was designed to characterize a different AIE model, namely, intermittent exposure to a single bottle of 10% ethanol as the only source of fluids on a 2 days on/2 days off (water days) schedule, and to determine whether this AIE exposure model would produce changes in hormonal and neuroimmune responsiveness to challenges of differing modalities. Assessments of ethanol intake as well as blood and brain ethanol concentrations (BECs and BrECs, respectively) in adult male and female rats (Experiment 1) revealed that BECs and BrECs peaked following access to ethanol for a 2 h period when assessed 1 h into the dark cycle. Experiment 2 revealed age differences in ethanol intake, BECs, and BrECs following a 2 h access to ethanol (1 h into the dark cycle), with adolescents ingesting more ethanol and reaching higher BECs as well as BrECs than adults. In Experiment 3, intermittent exposure to a single bottle of 10% ethanol for 10 cycles of 2 days on/2 days off was initiated either in early or late adolescence, followed by an acute systemic immune challenge with lipopolysaccharide (LPS) in adulthood. LPS increased corticosterone and progesterone levels regardless of sex and prior ethanol history, whereas an LPS-induced increase in cytokine gene expression in the hippocampus was evident only in ethanol-exposed males and females, with females who underwent early exposure to ethanol being more affected than their later-exposed counterparts. In Experiment 4, intermittent ethanol exposure in females was initiated either in adolescence or adulthood and lasted for 12 ethanol exposure cycles. Then, behavioral (freezing behavior), hormonal (corticosterone and progesterone levels), and neuroimmune (cytokine gene expression in the PVN, amygdala, and hippocampus) responses to novel environments (mild stressors) and shock (intense stressors) were assessed. More pronounced behavioral and hormonal changes, as well as changes in cytokine gene expression, were evident in the shock condition than following placement in the novel environment, with prior history of ethanol exposure not playing a substantial role. Interleukin (IL)-1β gene expression was enhanced by shock in the PVN, whereas shock-induced increases in IL-6 gene expression were evident in the hippocampus. Together, these findings demonstrate that our intermittent adolescent exposure model enhances responsiveness to immune but not stress challenges, with females being more vulnerable to this AIE effect than males.

Analysis of the influences of social isolation on cognition and the therapeutic potential of deep brain stimulation in a mouse model

Background

Social interaction is a fundamental human need. Social isolation (SI) can have negative effects on both emotional and cognitive function. However, it is currently unclear how age and the duration of SI affect emotion and recognition function. In addition, there is no specific treatment for the effects of SI.

Methods

The adolescence or adult mice were individually housed in cages for 1, 6 or 12 months and for 2 months to estabolish SI mouse model. We investigated the effects of SI on behavior in mice at different ages and under distinct durations of SI, and we explored the possible underlying mechanisms. Then we performed deep brain stimulation (DBS) to evaluate its influences on SI induced behavioral abnormalities.

Results

We found that social recognition was affected in the short term, while social preference was damaged by extremely long periods of SI. In addition to affecting social memory, SI also affects emotion, short-term spatial ability and learning willingness in mice. Myelin was decreased significantly in the medial prefrontal cortex (mPFC) and dorsal hippocampus of socially isolated mice. Cellular activity in response to social stimulation in both areas was impaired by social isolation. By stimulating the mPFC using DBS, we found that DBS alleviated cellular activation disorders in the mPFC after long-term SI and improved social preference in mice.

Conclusion

Our results suggest that the therapeutic potential of stimulating the mPFC with DBS in individuals with social preference deficits caused by long-term social isolation, as well as the effects of DBS on the cellular activity and density of OPCs.

Delay eyeblink conditioning performance and brain-wide c-Fos expression in male and female mice

Delay eyeblink conditioning has been extensively used to study associative learning and the cerebellar circuits underlying this task have been largely identified. However, there is a little knowledge on how factors such as strain, sex and innate behaviour influence performance during this type of learning. In this study, we used male and female mice of C57BL/6J (B6) and B6CBAF1 strains to investigate the effect of sex, strain and locomotion in delay eyeblink conditioning. We performed a short and a long delay eyeblink conditioning paradigm and used a c-Fos immunostaining approach to explore the involvement of different brain areas in this task. We found that both B6 and B6CBAF1 females reach higher learning scores compared to males in the initial stages of learning. This sex-dependent difference was no longer present as the learning progressed. Moreover, we found a strong positive correlation between learning scores and voluntary locomotion irrespective of the training duration. c-Fos immunostainings after the short paradigm showed positive correlations between c-Fos expression and learning scores in the cerebellar cortex and brainstem, as well as previously unreported areas. By contrast, after the long paradigm, c-Fos expression was only significantly elevated in the brainstem. Taken together, we show that differences in voluntary locomotion and activity across brain areas correlate with performance in delay eyeblink conditioning across strains and sexes.