Male Mouse Brain Research Articles

Machine learning-based high-frequency neuronal spike reconstruction from low-frequency and low-sampling-rate recordings

Recording neuronal activity using multiple electrodes has been widely used to understand the functional mechanisms of the brain. Increasing the number of electrodes allows us to decode more variety of functionalities. However, handling massive amounts of multichannel electrophysiological data is still challenging due to the limited hardware resources and unavoidable thermal tissue damage. Here, we present machine learning (ML)-based reconstruction of high-frequency neuronal spikes from subsampled low-frequency band signals. Inspired by the equivalence between high-frequency restoration and super-resolution in image processing, we applied a transformer ML model to neuronal data recorded from both in vitro cultures and in vivo male mouse brains. Even with the x8 downsampled datasets, our trained model reasonably estimated high-frequency information of spiking activity, including spike timing, waveform, and network connectivity. With our ML-based data reduction applicable to existing multichannel recording hardware while achieving neuronal signals of broad bandwidths, we expect to enable more comprehensive analysis and control of brain functions.

Specific and Nonuniform Brain States during Cold Perception in Mice.

The quest to decode the complex supraspinal mechanisms that integrate cutaneous thermal information in the central system is still ongoing. The dorsal horn of the spinal cord is the first hub that encodes thermal input which is then transmitted to brain regions via the spinothalamic and thalamocortical pathways. So far, our knowledge about the strength of the interplay between the brain regions during thermal processing is limited. To address this question, we imaged the brains of adult awake male mice in resting state using functional ultrasound imaging during plantar exposure to constant and varying temperatures. Our study reveals for the first time the following: (1) a dichotomy in the response of the somatomotor-cingulate cortices and the hypothalamus, which was never described before, due to the lack of appropriate tools to study such regions with both good spatial and temporal resolutions. (2) We infer that cingulate areas may be involved in the affective responses to temperature changes. (3) Colder temperatures (ramped down) reinforce the disconnection between the somatomotor-cingulate and hypothalamus networks. (4) Finally, we also confirm the existence in the mouse brain of a brain mode characterized by low cognitive strength present more frequently at resting neutral temperature. The present study points toward the existence of a common hub between somatomotor and cingulate regions, whereas hypothalamus functions are related to a secondary network.

Transcriptional and epigenetic dysregulation impairs generation of proliferative neural stem and progenitor cells during brain aging.

The decline in stem cell function during aging may affect the regenerative capacity of mammalian organisms; however, the gene regulatory mechanism underlying this decline remains unclear. Here we show that the aging of neural stem and progenitor cells (NSPCs) in the male mouse brain is characterized by a decrease in the generation efficacy of proliferative NSPCs rather than the changes in lineage specificity of NSPCs. We reveal that the downregulation of age-dependent genes in NSPCs drives cell aging by decreasing the population of actively proliferating NSPCs while increasing the expression of quiescence markers. We found that epigenetic deregulation of the MLL complex at promoters leads to transcriptional inactivation of age-dependent genes, highlighting the importance of the dynamic interaction between histone modifiers and gene regulatory elements in regulating transcriptional program of aging cells. Our study sheds light on the key intrinsic mechanisms driving stem cell aging through epigenetic regulators and identifies potential rejuvenation targets that could restore the function of aging stem cells.

Mutations associated with autism lead to similar synaptic and behavioral alterations in both sexes of male and female mouse brain

Autism spectrum disorder (ASD) is a neurodevelopmental disorder based on synaptic abnormalities. The estimated prevalence rate of male individuals diagnosed with ASD prevails over females is in a proportion of 4:1. Consequently, males remain the main focus in ASD studies in clinical and experimental settings. Meanwhile, some studies point to an underestimation of this disorder in females. In this work, we studied the sex differences of the synaptic and behavioral phenotypes of ASD mouse models. Juvenile male and female Shank3Δ4–22 and Cntnap2−/− mutant mice and their WT littermates were used in the experiments. The animals were subjected to a Three-Chamber Sociability Test, then euthanized, and the whole cortex was used for the evaluation of the synaptic phenotype. Protein levels of glutamatergic (NR1) and GABAergic (GAD1 and VGAT) neuronal markers were measured. Protein level of synaptophysin (Syp) was also measured. Dendritic spine density in somatosensory neurons was analyzed by Golgi staining methods. Spine Density and GAD1, NR1, VGAT, and Syp levels were significantly reduced in Shank3Δ4–22 and Cntnap2−/− mice compared to the control group irrespective of sex, indicating impaired synaptic development in the mutant mice. These results were consistent with the lack of differences in the three-chamber sociability test between male and female mice. In conclusion, female ASD mice of both mutations undergo similar synaptic aberrations as their male counterparts and need to be studied along with the male animals. Finally, this work urges the psychiatry scientific community to use both sexes in their investigations.

Sexually dimorphic murine brain uptake of the 18 kDa translocator protein PET radiotracer [18F]LW223.

The 18 kDa translocator protein is a well-known biomarker of neuroinflammation, but also plays a role in homeostasis. PET with 18 kDa translocator protein radiotracers [11C]PBR28 in humans and [18F]GE180 in mice has demonstrated sex-dependent uptake patterns in the healthy brain, suggesting sex-dependent 18 kDa translocator protein expression, although humans and mice had differing results. This study aimed to assess whether the 18 kDa translocator protein PET radiotracer [18F]LW223 exhibited sexually dimorphic uptake in healthy murine brain and peripheral organs. Male and female C57Bl6/J mice (13.6 ± 5.4 weeks, 26.8 ± 5.4 g, mean ± SD) underwent 2 h PET scanning post-administration of [18F]LW223 (6.7 ± 3.6 MBq). Volume of interest and parametric analyses were performed using standard uptake values (90-120 min). Statistical differences were assessed by unpaired t-test or two-way ANOVA with Šidak's test (alpha = 0.05). The uptake of [18F]LW223 was significantly higher across multiple regions of the male mouse brain, with the most pronounced difference detected in hypothalamus (P < 0.0001). Males also exhibited significantly higher [18F]LW223 uptake in the heart when compared to females (P = 0.0107). Data support previous findings on sexually dimorphic 18 kDa translocator protein radiotracer uptake patterns in mice and highlight the need to conduct sex-controlled comparisons in 18 kDa translocator protein PET imaging studies.

Exercise combined with postbiotics treatment results in synergistic improvement of mitochondrial function in the brain of male transgenic mice for Alzheimer’s disease

BackgroundIt has been suggested that exercise training and postbiotic supplement could decelerate the progress of functional and biochemical deterioration in double transgenic mice overexpresses mutated forms of the genes for human amyloid precursor protein (APPsw) and presenilin 1 (m146L) (APP/PS1TG). Our earlier published data indicated that the mice performed better than controls on the Morris Maze Test parallel with decreased occurrence of amyloid-β plaques in the hippocampus. We investigated the neuroprotective and therapeutic effects of high-intensity training and postbiotic supplementation.MethodsThirty-two adult APP/PS1TG mice were randomly divided into four groups: (1) control, (2) high-intensity training (3) postbiotic, (4) combined (training and postbiotic) treatment for 20 weeks. In this study, the whole hemibrain without hippocampus was used to find molecular traits explaining improved brain function. We applied qualitative RT-PCR for gene expression, Western blot for protein level, and Zymography for LONP1 activity. Disaggregation analysis of Aβ-40 was performed in the presence of Lactobacillus acidophilus and Bifidobacterium longum lysate.ResultsWe found that exercise training decreased Alzheimer’s Disease (AD)-related gene expression (NF-kB) that was not affected by postbiotic treatment. The preparation used for postbiotic treatment is composed of tyndallized Bifidobacterium longum and Lactobacillus acidophilus. Both of the postbiotics effectively disaggregated amyloid-β/Aβ-40 aggregates by chelating Zn2+ and Cu2+ ions. The postbiotic treatment decreased endogenous human APPTG protein expression and mouse APP gene expression in the hemibrains. In addition, the postbiotic treatment elevated mitochondrial LONP1 activity as well.ConclusionOur findings revealed distinct mechanisms behind improved memory performance in the whole brain: while exercise training modulates NF-kB signaling pathway regulating immune response until postbiotic diminishes APP gene expression, disaggregates pre-existing amyloid-β plaques and activates mitochondrial protein quality control in the region of brain out of hippocampus. Using the above treatments complements and efficiently slows down the development of AD.

Evidence for increased parallel information transmission in human brain networks compared to macaques and male mice

Brain communication, defined as information transmission through white-matter connections, is at the foundation of the brain’s computational capacities that subtend almost all aspects of behavior: from sensory perception shared across mammalian species, to complex cognitive functions in humans. How did communication strategies in macroscale brain networks adapt across evolution to accomplish increasingly complex functions? By applying a graph- and information-theory approach to assess information-related pathways in male mouse, macaque and human brains, we show a brain communication gap between selective information transmission in non-human mammals, where brain regions share information through single polysynaptic pathways, and parallel information transmission in humans, where regions share information through multiple parallel pathways. In humans, parallel transmission acts as a major connector between unimodal and transmodal systems. The layout of information-related pathways is unique to individuals across different mammalian species, pointing at the individual-level specificity of information routing architecture. Our work provides evidence that different communication patterns are tied to the evolution of mammalian brain networks.

Effect of Iron Oxide Nanoparticles Prepared by Chemical Method on the Kidneys, Liver and Brain of Male Mice

This study was conducted to investigate the toxic effect of Fe2O3 nanoparticles on the histological changes of the vital organs of male mice. The iron oxide nanomaterials were prepared by chemical method; several doses of it were used at different concentrations, which are 12, 10, 8, 6%. The dose is administered to the mice orally every 48 hours for a period of 60 days. The mice were divided into 6 groups in addition to the control group during the mentioned period; weights were taken for all groups throughout the experiment period. After the completion of the experimental period, the mice of all the mentioned groups were killed. The results of the histological examination with the first and second concentrations did not show any toxic effects or changes in the functional structures of the mentioned organs. while slight changes appeared in the high concentrations of nanoparticles, as it was found that there was some blood congestion and inflammation in the kidneys. There is also congestion in parts of the liver with enlargement in some cells, as well as congestion in the brain, at concentrations of 12.10%. While no structural changes appeared in the first and second concentrations, also in the control group, no changes appeared in the functional structure of the above members. From the results of the study, we conclude that the use of high concentrations of nanoparticles of iron oxide may lead to changes in the functional structures of the kidneys, liver and brain, and may lead to toxic effects on the rest of the body.

Sexual dimorphism in synaptic inputs to the mouse amygdala and orbital cortex.

The medial amygdala (MeA) is a sexually dimorphic brain region that regulates fear responses, emotional memories, and social behaviors. It is known to be larger and contains more cells in males. The MeA integrates information through input connections from olfactory regions, bed nucleus of the stria terminalis, ventral hippocampus, and thalamic and hypothalamic structures. We hypothesize that in addition to the size differences, there are differences in regional connectivity between the sexes. In this study, we utilized G-deleted rabies monosynaptic retrograde tracing to compare amygdala presynaptic cells in male and female whole mouse brains. We report differences in connection patterns to the amygdala, with higher overall connectivity (presynaptic per starter) in males and a larger fraction of inputs originating from the bed nucleus of the stria terminalis, lateral septum, and medial preoptic area. Furthermore, we examined input connections to the orbital cortex (ORB), a brain region shown to be larger in volume in females, and found the opposite trend, where females had more total inputs. Together, our findings extend the evidence for sexual dimorphism in the brain to the neuronal wiring pattern, with likely impacts on behavior and disease susceptibility.

Genetic Reduction of Insulin Signaling Mitigates Amyloid-β Deposition by Promoting Expression of Extracellular Matrix Proteins in the Brain.

The insulin/IGF-1 signaling (IIS) regulates a wide range of biological processes, including aging and lifespan, and has also been implicated in the pathogenesis of Alzheimer's disease (AD). We and others have reported that reduced signaling by genetic ablation of the molecules involved in IIS (e.g., insulin receptor substrate 2 [IRS-2]) markedly mitigates amyloid plaque formation in the brains of mouse models of AD, although the molecular underpinnings of the amelioration remain unsolved. Here, we revealed, by a transcriptomic analysis of the male murine cerebral cortices, that the expression of genes encoding extracellular matrix (ECM) was significantly upregulated by the loss of IRS-2. Insulin signaling activity negatively regulated the phosphorylation of Smad2 and Smad3 in the brain, and suppressed TGF-β/Smad-dependent expression of a subset of ECM genes in brain-derived cells. The ECM proteins inhibited Aβ fibril formation in vitro, and IRS-2 deficiency suppressed the aggregation process of Aβ in the brains of male APP transgenic mice as revealed by injection of aggregation seeds in vivo Our results propose a novel mechanism in AD pathophysiology whereby IIS modifies Aβ aggregation and amyloid pathology by altering the expression of ECM genes in the brain.SIGNIFICANCE STATEMENT The insulin/IGF-1 signaling (IIS) has been recognized as a regulator of aging, a leading risk factor for the onset of Alzheimer's disease (AD). In AD mouse models, genetic deletion of key IIS molecules markedly reduces the amyloid plaque formation in the brain, although the molecular underpinnings of this amelioration remain elusive. We found that the deficiency of insulin receptor substrate 2 leads to an increase in the expression of various extracellular matrices (ECMs) in the brain, potentially through TGF-β/Smad signaling. Furthermore, some of those ECMs exhibited the potential to inhibit amyloid plaque accumulation by disrupting the formation of Aβ fibrils. This study presents a novel mechanism by which IIS regulates Aβ accumulation, which may involve altered brain ECM expression.

Ferulic Acid reduces amyloid beta mediated neuroinflammation through modulation of Nurr1 expression in microglial cells.

Microglial cells (MGCs) serve as the resident macrophages in the brain and spinal cord, acting as the first line of immune defense against pathological changes. With various phenotypes, they can shift from a homeostatic state to a reactive state or transit from a reactive to a non-inflammatory reactive state (alternative homeostatic). A well-timed transit is crucial in limiting excessive microglial reaction and promoting the healing process. Studies indicate that increased Nurr1 expression promotes anti-neuroinflammatory responses in the brain. In this study, we investigated the possible role of ferulic acid (FA) in facilitating microglia transition due to its anti-inflammatory and Nurr1-inducing effects. MGCs were extracted from the brains of male NMRI mice at postnatal day 2 (P2) and cultured with or without FA and beta-amyloid (Aβ). Real-time qRT-PCR was conducted to measure the expressions of Nurr1, IL-1β, and IL-10 genes. Immunostaining was performed to determine the number of NURR1-positive cells, and the ramification index (RI) of MGCs was calculated using Image J software. Treating MGCs with FA (50 μg/ml) induced Nurr1 and IL-10 expressions, while reducing the level of IL-1β in the absence of Aβ-stress. Further assessments on cells under Aβ-stress showed that FA treatment restored the IL-10 and Nurr1 levels, increased the RI of cells, and the number of NURR1-positive cells. Morphological assessments and measurements of the RI revealed that FA treatment reversed amoeboid and rod-like cells to a ramified state, which is specific morphology for non-inflammatory reactive microglia. To conclude, FA can provide potential alternative homeostatic transition in Aβ-reactive microglia by recruiting the NURR1 dependent anti-inflammatory responses. This makes it a promising therapeutic candidate for suppressing Aβ-induced neuroinflammatory responses in MGCs. Furthermore, given that FA has the ability to increase NURR1 levels in homeostatic microglia, it could be utilized as a preventative medication.

Brain mitochondrial diversity and network organization predict anxiety-like behavior in male mice

The brain and behavior are under energetic constraints, limited by mitochondrial energy transformation capacity. However, the mitochondria-behavior relationship has not been systematically studied at a brain-wide scale. Here we examined the association between multiple features of mitochondrial respiratory chain capacity and stress-related behaviors in male mice with diverse behavioral phenotypes. Miniaturized assays of mitochondrial respiratory chain enzyme activities and mitochondrial DNA (mtDNA) content were deployed on 571 samples across 17 brain areas, defining specific patterns of mito-behavior associations. By applying multi-slice network analysis to our brain-wide mitochondrial dataset, we identified three large-scale networks of brain areas with shared mitochondrial signatures. A major network composed of cortico-striatal areas exhibited the strongest mitochondria-behavior correlations, accounting for up to 50% of animal-to-animal behavioral differences, suggesting that this mito-based network is functionally significant. The mito-based brain networks also overlapped with regional gene expression and structural connectivity, and exhibited distinct molecular mitochondrial phenotype signatures. This work provides convergent multimodal evidence anchored in enzyme activities, gene expression, and animal behavior that distinct, behaviorally-relevant mitochondrial phenotypes exist across the male mouse brain.

Recruitment of Corticotropin-Releasing Hormone (CRH) Neurons in Categorically Distinct Stress Reactions in the Mouse Brain.

Corticotropin-releasing hormone (CRH) neurons in the paraventricular hypothalamic nucleus (PVH) are in the position to integrate stress-related information and initiate adaptive neuroendocrine-, autonomic-, metabolic- and behavioral responses. In addition to hypophyseotropic cells, CRH is widely expressed in the CNS, however its involvement in the organization of the stress response is not fully understood. In these experiments, we took advantage of recently available Crh-IRES-Cre;Ai9 mouse line to study the recruitment of hypothalamic and extrahypothalamic CRH neurons in categorically distinct, acute stress reactions. A total of 95 brain regions in the adult male mouse brain have been identified as containing putative CRH neurons with significant expression of tdTomato marker gene. With comparison of CRH mRNA and tdTomato distribution, we found match and mismatch areas. Reporter mice were then exposed to restraint, ether, high salt, lipopolysaccharide and predator odor stress and neuronal activation was revealed by FOS immunocytochemistry. In addition to a core stress system, stressor-specific areas have been revealed to display activity marker FOS. Finally, activation of CRH neurons was detected by colocalization of FOS in tdTomato expressing cells. All stressors resulted in profound activation of CRH neurons in the hypothalamic paraventricular nucleus; however, a differential activation of pattern was observed in CRH neurons in extrahypothalamic regions. This comprehensive description of stress-related CRH neurons in the mouse brain provides a starting point for a systematic functional analysis of the brain stress system and its relation to stress-induced psychopathologies.

Novel Isolation Method Reveals Sex-Specific Composition and Neurotoxicity of Small Extracellular Vesicles in a Mouse Model of Alzheimer's Disease.

We developed a new method to isolate small extracellular vesicles (sEVs) from male and female wild-type and 5xFAD mouse brains to investigate the sex-specific functions of sEVs in Alzheimer's disease (AD). A mass spectrometric analysis revealed that sEVs contained proteins critical for EV formation and Aβ. ExoView analysis showed that female mice contained more GFAP and Aβ-labeled sEVs, suggesting that a larger proportion of sEVs from the female brain is derived from astrocytes and/or more likely to bind to Aβ. Moreover, sEVs from female brains had more acid sphingomyelinase (ASM) and ceramide, an enzyme and its sphingolipid product important for EV formation and Aβ binding to EVs, respectively. We confirmed the function of ASM in EV formation and Aβ binding using co-labeling and proximity ligation assays, showing that ASM inhibitors prevented complex formation between Aβ and ceramide in primary cultured astrocytes. Finally, our study demonstrated that sEVs from female 5xFAD mice were more neurotoxic than those from males, as determined by impaired mitochondrial function (Seahorse assays) and LDH cytotoxicity assays. Our study suggests that sex-specific sEVs are functionally distinct markers for AD and that ASM is a potential target for AD therapy.

Effect of citicoline and transcranial direct current stimulation on depressive-like behaviors in mice & quot

Recent investigations revealed the positive role of transcranial direct current stimulation (tDCS) in the treatment of depressive-like behavior & quot. Citicoline is a dietary supplement. It acts as a neuroprotective factor for the treatment of neurological disorders. The aim of this research was to evaluate a possible interaction between tDCS and citicoline on the modulation of depressive-like behavior s & quot in male mice. For tDCS, an electrode was surgically implanted in the left prefrontal of the brain of male mice & quot. Acute restraint stress was induced by movement restraint for 4 h. Locomotor activity and depressive-like behaviors & quot were examined by open field test (OFT), forced swimming test (FST), and tail suspension test (TST). The results indicated that the intraperitoneal (i.p.) administration of citicoline, left prefrontal anodal tDCS, and co-treatment of citicoline and tDCS had no significant effect on locomotor activity. I.p. injection of citicoline (30 mg/kg) decreased immobility time in the FST and TST, showing an antidepressant-like effect & quot. Moreover, the application of left prefrontal anodal tDCS (0.2 mA) for 20 min induced antidepressant-like effect & quot by reducing immobility time in the FST and TST. Co-administration of citicoline (7 and 15 mg/kg) along with tDCS (0.1 mA) decreased immobility time in the FST and TST, indicating an antidepressant-like effect & quot. Therefore, it can be concluded that administration of citicoline in combination with tDCS enhanced the efficacy of tDCS for remedy of depressive-like behaviors & quot.

In Vivo Photoadduction of Anesthetic Ligands in Mouse Brain Markedly Extends Sedation and Hypnosis.

Photoaffinity ligands are best known as tools used to identify the specific binding sites of drugs to their molecular targets. However, photoaffinity ligands have the potential to further define critical neuroanatomic targets of drug action. In the brains of WT male mice, we demonstrate the feasibility of using photoaffinity ligands in vivo to prolong anesthesia via targeted yet spatially restricted photoadduction of azi-m-propofol (aziPm), a photoreactive analog of the general anesthetic propofol. Systemic administration of aziPm with bilateral near-ultraviolet photoadduction in the rostral pons, at the border of the parabrachial nucleus and locus coeruleus, produced a 20-fold increase in the duration of sedative and hypnotic effects compared with control mice without UV illumination. Photoadduction that missed the parabrachial-coerulean complex also failed to extend the sedative or hypnotic actions of aziPm and was indistinguishable from nonadducted controls. Paralleling the prolonged behavioral and EEG consequences of on target in vivo photoadduction, we conducted electrophysiologic recordings in rostral pontine brain slices. Using neurons within the locus coeruleus to further highlight the cellular consequences of irreversible aziPm binding, we demonstrate transient slowing of spontaneous action potentials with a brief bath application of aziPm that becomes irreversible on photoadduction. Together, these findings suggest that photochemistry-based strategies are a viable new approach for probing CNS physiology and pathophysiology.SIGNIFICANCE STATEMENT Photoaffinity ligands are drugs capable of light-induced irreversible binding, which have unexploited potential to identify the neuroanatomic sites of drug action. We systemically administer a centrally acting anesthetic photoaffinity ligand in mice, conduct localized photoillumination within the brain to covalently adduct the drug at its in vivo sites of action, and successfully enrich irreversible drug binding within a restricted 250 µm radius. When photoadduction encompassed the pontine parabrachial-coerulean complex, anesthetic sedation and hypnosis was prolonged 20-fold, thus illustrating the power of in vivo photochemistry to help unravel neuronal mechanisms of drug action.

Single-cell RNA-sequencing identifies disease-associated oligodendrocytes in male APP NL-G-F and 5XFAD mice

Alzheimer’s disease (AD) is associated with progressive neuronal degeneration as amyloid-beta (Aβ) and tau proteins accumulate in the brain. Glial cells were recently reported to play an important role in the development of AD. However, little is known about the role of oligodendrocytes in AD pathogenesis. Here, we describe a disease-associated subpopulation of oligodendrocytes that is present during progression of AD-like pathology in the male AppNL-G-F and male 5xFAD AD mouse brains and in postmortem AD human brains using single-cell RNA sequencing analysis. Aberrant Erk1/2 signaling was found to be associated with the activation of disease-associated oligodendrocytes (DAOs) in male AppNL-G-F mouse brains. Notably, inhibition of Erk1/2 signaling in DAOs rescued impaired axonal myelination and ameliorated Aβ-associated pathologies and cognitive decline in the male AppNL-G-F AD mouse model.

Inhibition of RPTPβ/ζ reduces chronic ethanol intake in adolescent mice and modulates ethanol effects on hippocampal neurogenesis and glial responses in a sex-dependent manner

Pleiotrophin (PTN) is a cytokine that modulates ethanol drinking and reward and regulates glial responses in different contexts. PTN is an inhibitor of Receptor Protein Tyrosine Phosphatase (RPTP) β/ζ. Inhibition of RPTPβ/ζ reduces binge-like drinking in adult male mice. Whether inhibition of RPTPβ/ζ is effective in reducing ethanol consumption during adolescence and in both sexes remained to be studied. In this work, male and female adolescent mice underwent an intermittent access to ethanol (IAE) 2-bottle choice protocol. Treatment with MY10 (60 mg/kg, i.g.), a small-molecule RPTPβ/ζ inhibitor, reduced chronic 3-week ethanol consumption only in male mice. We detected an ethanol-induced overall decrease in hippocampal GFAPir and Iba1ir, independently of the treatment received, suggesting that RPTPβ/ζ is not key in the regulation of IAE-induced glial responses. However, we found a significant negative correlation between the size of microglial cells and the number of hippocampal neuronal progenitors only in male mice after IAE. This correlation was disrupted by treatment with MY10 before each drinking session, which may be related to the ability of MY10 to regulate the intensity of the perineuronal nets (PNNs) in the hippocampus in a sex-dependent manner. The data show for the first time that inhibition of RPTPβ/ζ reduces chronic voluntary ethanol consumption in adolescent mice in a sex-dependent manner. In addition, we show evidence for sex-specific differences in the effects of IAE on glial responses and hippocampal neurogenesis, which may be related to different actions of the RPTPβ/ζ signalling pathway in the brains of male and female mice.

CSF1R inhibitors induce a sex-specific resilient microglial phenotype and functional rescue in a tauopathy mouse model

Microglia are central to pathogenesis in many neurological conditions. Drugs targeting colony-stimulating factor-1 receptor (CSF1R) to block microglial proliferation in preclinical disease models have shown mixed outcomes, thus the therapeutic potential of this approach remains unclear. Here, we show that CSF1R inhibitors given by multiple dosing paradigms in the Tg2541 tauopathy mouse model cause a sex-independent reduction in pathogenic tau and reversion of non-microglial gene expression patterns toward a normal wild type signature. Despite greater drug exposure in male mice, only female mice have functional rescue and extended survival. A dose-dependent upregulation of immediate early genes and neurotransmitter dysregulation are observed in the brains of male mice only, indicating that excitotoxicity may preclude functional benefits. Drug-resilient microglia in male mice exhibit morphological and gene expression patterns consistent with increased neuroinflammatory signaling, suggesting a mechanistic basis for sex-specific excitotoxicity. Complete microglial ablation is neither required nor desirable for neuroprotection and therapeutics targeting microglia must consider sex-dependent effects.

Sex differences in the coexpression of prokineticin receptor 2 and gonadal steroids receptors in mice.

Loss-of-function mutations in prokineticin 2 (PROK2) and the cognate receptor prokineticin receptor 2 (PROKR2) genes have been implicated in reproductive deficits characteristic of Kallmann Syndrome (KS). Knock out of Prokr2 gene produces the KS-like phenotype in mice resulting in impaired migration of gonadotropin releasing hormone (GnRH) neurons, olfactory bulb dysgenesis, and infertility. Beyond a developmental role, pharmacological and genetic studies have implicated PROKR2 in the control of the estrous cycle in mice. However, PROKR2 is expressed in several reproductive control sites but the brain nuclei associated with reproductive control in adult mice have not been defined. We set out to determine if ProkR2 neurons in both male and female mouse brains directly sense changes in the gonadal steroids milieu. We focused on estrogen receptor α (ERα) and androgen receptor (AR) due to their well-described function in reproductive control via actions in the brain. We found that the ProkR2-Cre neurons in the posterior nucleus of the amygdala have the highest colocalization with ERα and AR in a sex-specific manner. Few colocalization was found in the lateral septum and in the bed nucleus of the stria terminalis, and virtually no colocalization was observed in the medial amygdala. Our findings indicate that the posterior nucleus of the amygdala is the main site where PROKR2 neurons may regulate aspects of the reproductive function and social behavior in adult mice.