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Scientific Reports May 2024Anxiety is among the most fundamental mammalian behaviors. Despite the physiological and pathological importance, its underlying neural mechanisms remain poorly...
Anxiety is among the most fundamental mammalian behaviors. Despite the physiological and pathological importance, its underlying neural mechanisms remain poorly understood. Here, we recorded the activity of olfactory bulb (OB) and medial prefrontal cortex (mPFC) of rats, which are critical structures to brain's emotional processing network, while exploring different anxiogenic environments. Our results show that presence in anxiogenic contexts increases the OB and mPFC regional theta activities. Also, these local activity changes are associated with enhanced OB-mPFC theta power- and phase-based functional connectivity as well as OB-to-mPFC information transfer. Interestingly, these effects are more prominent in the unsafe zones of the anxiogenic environments, compared to safer zones. This consistent trend of changes in diverse behavioral environments as well as local and long-range neural activity features suggest that the dynamics of OB-mPFC circuit theta oscillations might underlie different types of anxiety behaviors, with possible implications for anxiety disorders.
Topics: Prefrontal Cortex; Animals; Anxiety; Theta Rhythm; Olfactory Bulb; Male; Rats; Rats, Sprague-Dawley; Behavior, Animal
PubMed: 38802558
DOI: 10.1038/s41598-024-63101-z -
Cell Reports May 2024In the adult brain, structural and functional parameters, such as synaptic sizes and neuronal firing rates, follow right-skewed and heavy-tailed distributions. While...
In the adult brain, structural and functional parameters, such as synaptic sizes and neuronal firing rates, follow right-skewed and heavy-tailed distributions. While this organization is thought to have significant implications, its development is still largely unknown. Here, we address this knowledge gap by investigating a large-scale dataset recorded from the prefrontal cortex and the olfactory bulb of mice aged 4-60 postnatal days. We show that firing rates and spike train interactions have a largely stable distribution shape throughout the first 60 postnatal days and that the prefrontal cortex displays a functional small-world architecture. Moreover, early brain activity exhibits an oligarchical organization, where high-firing neurons have hub-like properties. In a neural network model, we show that analogously right-skewed and heavy-tailed synaptic parameters are instrumental to consistently recapitulate the experimental data. Thus, functional and structural parameters in the developing brain are already extremely distributed, suggesting that this organization is preconfigured and not experience dependent.
PubMed: 38795344
DOI: 10.1016/j.celrep.2024.114267 -
International Journal of Molecular... May 2024Chronic environmental exposure to toxic heavy metals, which often occurs as a mixture through occupational and industrial sources, has been implicated in various...
Chronic environmental exposure to toxic heavy metals, which often occurs as a mixture through occupational and industrial sources, has been implicated in various neurological disorders, including Parkinsonism. Vanadium pentoxide (VO) typically presents along with manganese (Mn), especially in welding rods and high-capacity batteries, including electric vehicle batteries; however, the neurotoxic effects of vanadium (V) and Mn co-exposure are largely unknown. In this study, we investigated the neurotoxic impact of MnCl, VO and MnCl-VO co-exposure in an animal model. C57BL/6 mice were intranasally administered either de-ionized water (vehicle), MnCl (252 µg) alone, VO (182 µg) alone, or a mixture of MnCl (252 µg) and VO (182 µg) three times a week for up to one month. Following exposure, we performed behavioral, neurochemical, and histological studies. Our results revealed dramatic decreases in olfactory bulb (OB) weight and levels of tyrosine hydroxylase, dopamine, and 3,4-dihydroxyphenylacetic acid in the treatment groups compared to the control group, with the Mn/V co-treatment group producing the most significant changes. Interestingly, increased levels of α-synuclein expression were observed in the substantia nigra (SN) of treated animals. Additionally, treatment groups exhibited locomotor deficits and olfactory dysfunction, with the co-treatment group producing the most severe deficits. The treatment groups exhibited increased levels of the oxidative stress marker 4-hydroxynonenal in the striatum and SN, as well as the upregulation of the pro-apoptotic protein PKCδ and accumulation of glomerular astroglia in the OB. The co-exposure of animals to Mn/V resulted in higher levels of these metals compared to other treatment groups. Taken together, our results suggest that co-exposure to Mn/V can adversely affect the olfactory and nigral systems. These results highlight the possible role of environmental metal mixtures in the etiology of Parkinsonism.
Topics: Animals; Mice; Manganese; Mice, Inbred C57BL; Vanadium; Manganese Compounds; Male; Olfactory Bulb; Dopamine; Vanadium Compounds; Oxidative Stress; Parkinsonian Disorders; alpha-Synuclein; Chlorides; Tyrosine 3-Monooxygenase; Aldehydes; Substantia Nigra; Disease Models, Animal; 3,4-Dihydroxyphenylacetic Acid
PubMed: 38791326
DOI: 10.3390/ijms25105285 -
Current Issues in Molecular Biology May 2024Type I interferon signaling (IFN-I) perturbations are major drivers of COVID-19. Dysregulated IFN-I in the brain, however, has been linked to both reduced cognitive...
Type I interferon signaling (IFN-I) perturbations are major drivers of COVID-19. Dysregulated IFN-I in the brain, however, has been linked to both reduced cognitive resilience and neurodegenerative diseases such as Alzheimer's. Previous works from our group have proposed a model where peripheral induction of IFN-I may be relayed to the CNS, even in the absence of fulminant infection. The aim of our study was to identify significantly enriched IFN-I signatures and genes along the transolfactory route, utilizing published datasets of the nasal mucosa and olfactory bulb amygdala transcriptomes of COVID-19 patients. We furthermore sought to identify these IFN-I signature gene networks associated with Alzheimer's disease pathology and risk. Gene expression data involving the nasal epithelium, olfactory bulb, and amygdala of COVID-19 patients and transcriptomic data from Alzheimer's disease patients were scrutinized for enriched Type I interferon pathways. Gene set enrichment analyses and gene-Venn approaches were used to determine genes in IFN-I enriched signatures. The Agora web resource was used to identify genes in IFN-I signatures associated with Alzheimer's disease risk based on its aggregated multi-omic data. For all analyses, false discovery rates (FDR) <0.05 were considered statistically significant. Pathways associated with type I interferon signaling were found in all samples tested. Each type I interferon signature was enriched by IFITM and OAS family genes. A 14-gene signature was associated with COVID-19 CNS and the response to Alzheimer's disease pathology, whereas nine genes were associated with increased risk for Alzheimer's disease based on Agora. Our study provides further support to a type I interferon signaling dysregulation along the extended olfactory network as reconstructed herein, ranging from the nasal epithelium and extending to the amygdala. We furthermore identify the 14 genes implicated in this dysregulated pathway with Alzheimer's disease pathology, among which HLA-C, HLA-B, HLA-A, PSMB8, IFITM3, HLA-E, IFITM1, OAS2, and MX1 as genes with associated conferring increased risk for the latter. Further research into its druggability by IFNb therapeutics may be warranted.
PubMed: 38785545
DOI: 10.3390/cimb46050277 -
Scientific Reports May 2024Most terrestrial mammals have a vomeronasal system to detect specific chemicals. The peripheral organ of this system is a vomeronasal organ (VNO) opening to the incisive...
Most terrestrial mammals have a vomeronasal system to detect specific chemicals. The peripheral organ of this system is a vomeronasal organ (VNO) opening to the incisive duct, and its primary integrative center is an accessory olfactory bulb (AOB). The VNO in seals is thought to be degenerated like whales and manatees, unlike otariids, because of the absence of the AOB. However, olfaction plays pivotal roles in seals, and thus we conducted a detailed morphological evaluation of the vomeronasal system of three harbor seals (Phoca vitulina). The VNO lumen was not found, and the incisive duct did not open into the oral cavity but was recognized as a fossa on the anteroventral side of the nasal cavity. This fossa is rich in mucous glands that secrete acidic mucopolysaccharides, which might originate from the vomeronasal glands. The olfactory bulb consisted only of a main olfactory bulb that received projections from the olfactory mucosa, but an AOB region was not evident. These findings clarified that harbor seals do not have a VNO to detect some chemicals, but the corresponding region is a specialized secretory organ.
Topics: Animals; Vomeronasal Organ; Phoca; Nasal Cavity; Olfactory Bulb; Mucus; Olfactory Mucosa; Male; Smell; Female
PubMed: 38783070
DOI: 10.1038/s41598-024-62711-x -
NPJ Parkinson's Disease May 2024Parkinson's disease (PD) is a neurodegenerative disease characterized by progressive motor symptoms and alpha-synuclein (αsyn) aggregation in the nervous system. For...
Parkinson's disease (PD) is a neurodegenerative disease characterized by progressive motor symptoms and alpha-synuclein (αsyn) aggregation in the nervous system. For unclear reasons, PD patients with certain GBA1 mutations (GBA-PD) have a more aggressive clinical progression. Two testable hypotheses that can potentially account for this phenomenon are that GBA1 mutations promote αsyn spread or drive the generation of highly pathogenic αsyn polymorphs (i.e., strains). We tested these hypotheses by treating homozygous GBA1 D409V knockin (KI) mice with human α-syn-preformed fibrils (PFFs) and treating wild-type mice (WT) with several αsyn-PFF polymorphs amplified from brain autopsy samples collected from patients with idiopathic PD and GBA-PD patients with either homozygous or heterozygous GBA1 mutations. Robust phosphorylated-αsyn (PSER129) positive pathology was observed at the injection site (i.e., the olfactory bulb granule cell layer) and throughout the brain six months following PFF injection. The PFF seeding efficiency and degree of spread were similar regardless of the mouse genotype or PFF polymorphs. We found that PFFs amplified from the human brain, regardless of patient genotype, were generally more effective seeders than wholly synthetic PFFs (i.e., non-amplified); however, PFF concentration differed between these two studies, which might also account for the observed differences. To investigate whether the molecular composition of pathology differed between different seeding conditions, we performed Biotinylation by Antibody Recognition on PSER129 (BAR-PSER129). We found that for BAR-PSER129, the endogenous PSER129 pool dominated identified interactions, and thus, very few potential interactions were explicitly identified for seeded pathology. However, we found Dynactin Subunit 2 (Dctn2) interaction was shared across all PFF conditions, and NCK Associated Protein 1 (Nckap1) and Adaptor Related Protein Complex 3 Subunit Beta 2 (Ap3b2) were unique to PFFs amplified from GBA-PD brains of heterozygous mutation carriers. In conclusion, both the genotype and αsyn strain had little effect on overall seeding efficacy and global PSER129-interactions.
PubMed: 38773124
DOI: 10.1038/s41531-024-00679-1 -
BioRxiv : the Preprint Server For... May 2024Inhibitory circuits in the mammalian olfactory bulb (OB) dynamically reformat olfactory information as it propagates from peripheral receptors to downstream cortex. To...
Inhibitory circuits in the mammalian olfactory bulb (OB) dynamically reformat olfactory information as it propagates from peripheral receptors to downstream cortex. To gain mechanistic insight into how specific OB interneuron types support this sensory processing, we examine unitary synaptic interactions between excitatory mitral and tufted cells (MTCs), the OB projection cells, and a conserved population of anaxonic external plexiform layer interneurons (EPL-INs) using pair and quartet whole-cell recordings in acute mouse brain slices. Physiological, morphological, neurochemical, and synaptic analyses divide EPL-INs into distinct subtypes and reveal that parvalbumin-expressing fast-spiking EPL-INs (FSIs) perisomatically innervate MTCs with release-competent dendrites and synaptically detonate to mediate fast, short-latency recurrent and lateral inhibition. Sparse MTC synchronization supralinearly increases this high-fidelity inhibition, while sensory afferent activation combined with single-cell silencing reveals that individual FSIs account for a substantial fraction of total network-driven MTC lateral inhibition. OB output is thus powerfully shaped by detonation-driven high-fidelity perisomatic inhibition.
PubMed: 38766161
DOI: 10.1101/2024.05.07.592874 -
Molecular Brain May 2024CD11c-positive (CD11c) microglia have attracted considerable attention because of their potential implications in central nervous system (CNS) development, homeostasis,...
CD11c-positive (CD11c) microglia have attracted considerable attention because of their potential implications in central nervous system (CNS) development, homeostasis, and disease. However, the spatiotemporal dynamics of the proportion of CD11c microglia in individual CNS regions are poorly understood. Here, we investigated the proportion of CD11c microglia in six CNS regions (forebrain, olfactory bulb, diencephalon/midbrain, cerebellum, pons/medulla, and spinal cord) from the developmental to adult stages by flow cytometry and immunohistochemical analyses using a CD11c reporter transgenic mouse line, Itgax-Venus. We found that the proportion of CD11c microglia in total microglia varied between CNS regions during postnatal development. Specifically, the proportion was high in the olfactory bulb and cerebellum at postnatal day P(4) and P7, respectively, and approximately half of the total microglia were CD11c. The proportion declined sharply in all regions to P14, and the low percentage persisted over P56. In the spinal cord, the proportion of CD11c microglia was also high at P4 and declined to P14, but increased again at P21 and thereafter. Interestingly, the distribution pattern of CD11c microglia in the spinal cord markedly changed from gray matter at P4 to white matter at P21. Collectively, our findings reveal the differences in the spatiotemporal dynamics of the proportion of CD11c microglia among CNS regions from early development to adult stages in normal mice. These findings improve our understanding of the nature of microglial heterogeneity and its dynamics in the CNS.
Topics: Animals; Microglia; Spinal Cord; Brain; Mice, Transgenic; Spatio-Temporal Analysis; Aging; CD11c Antigen; Mice, Inbred C57BL; Mice; Animals, Newborn
PubMed: 38762724
DOI: 10.1186/s13041-024-01098-2 -
Scientific Reports May 2024The phenomenon of contagious itch, observed in both humans and rodents, remains a topic of ongoing debate concerning its modulators and underlying pathways. This study...
The phenomenon of contagious itch, observed in both humans and rodents, remains a topic of ongoing debate concerning its modulators and underlying pathways. This study delves into the relationship between contagious itch and familiar olfactory cues, a non-visual factor contributing to this intriguing behavior. Our findings showed that contagious itch in observer mice occurs during physical interaction with the cagemate itch-demonstrator but not with a stranger demonstrator or in a non-physical encounter condition. Notably, itch-experienced observer mice displayed an increased contagious itch behavior, highlighting the relevance of itch-associated memory in this phenomenon. Furthermore, anosmic observer mice, whether itch-naïve or itch-experienced, displayed no contagious itch behavior. These results demonstrate that the familiar olfactory cues, specifically cagemate body odors, are required for contagious itch behaviors in mice. In line with these behavioral findings, our study reveals increased activity in brain regions associated with olfaction, emotion, and memory during contagious itch, including the olfactory bulb, the amygdala, the hypothalamus, and the hippocampus, with this activity diminished in anosmic mice. In conclusion, our study unveils the critical role of familiar olfactory cues in driving contagious itch in mice, shedding light on the interplay between social factors, sensory perception, and memory in this phenomenon.
Topics: Animals; Pruritus; Mice; Cues; Smell; Male; Behavior, Animal; Interpersonal Relations; Mice, Inbred C57BL; Odorants; Olfactory Bulb; Brain
PubMed: 38760368
DOI: 10.1038/s41598-024-61078-3 -
Scientific Reports May 2024Androgen deprivation therapy (ADT) is the core treatment for advanced prostate cancer (PCa), with a proven survival benefit. ADT lowers circulating testosterone levels...
Androgen deprivation therapy (ADT) is the core treatment for advanced prostate cancer (PCa), with a proven survival benefit. ADT lowers circulating testosterone levels throughout the body, but with it comes a variety of reported side effects including fatigue, muscle wastage, weight gain, hot flushes and importantly cognitive impairment, depression, and mood swings. Testosterone has a key role in brain masculinization, but its direct effects are relatively poorly understood, due both to the brain's extreme complexity and the fact that some of testosterone activities are driven via local conversion to oestrogen, especially during embryonic development. The exact roles, function, and location of the androgen receptor (AR) in the adult male brain are still being discovered, and therefore the cognitive side effects of ADT may be unrecognized or under-reported. The age of onset of several neurological diseases overlap with PCa, therefore, there is a need to separate ADT side effects from such co-morbidities. Here we analysed the activity and expression level of the AR in the adult mouse brain, using an ARE-Luc reporter mouse and immunohistochemical staining for AR in all the key brain regions via coronal slices. We further analysed our data by comparing to the Allen Mouse Brain Atlas. AR-driven luciferase activity and distinct nuclear staining for AR were seen in several key brain areas including the thalamus, hypothalamus, olfactory bulb, cerebral cortex, Purkinje cells of the cerebellum and the hindbrain. We describe and discuss the potential role of AR in these areas, to inform and enable extrapolation to potential side effects of ADT in humans.
Topics: Receptors, Androgen; Animals; Mice; Brain; Male
PubMed: 38750183
DOI: 10.1038/s41598-024-61733-9