Neuronal Glutamate Research Articles

Concerted transcriptional regulation of the morphogenesis of hypothalamic neurons by ONECUT3

Acquisition of specialized cellular features is controlled by the ordered expression of transcription factors (TFs) along differentiation trajectories. Here, we find a member of the Onecut TF family, ONECUT3, expressed in postmitotic neurons that leave their Ascl1+/Onecut1/2+ proliferative domain in the vertebrate hypothalamus to instruct neuronal differentiation. We combined single-cell RNA-seq and gain-of-function experiments for gene network reconstruction to show that ONECUT3 affects the polarization and morphogenesis of both hypothalamic GABA-derived dopamine and thyrotropin-releasing hormone (TRH)+ glutamate neurons through neuron navigator-2 (NAV2). In vivo, siRNA-mediated knockdown of ONECUT3 in neonatal mice reduced NAV2 mRNA, as well as neurite complexity in Onecut3-containing neurons, while genetic deletion of Onecut3/ceh-48 in C. elegans impaired neurocircuit wiring, and sensory discrimination-based behaviors. Thus, ONECUT3, conserved across neuronal subtypes and many species, underpins the polarization and morphological plasticity of phenotypically distinct neurons that descend from a common pool of Ascl1+ progenitors in the hypothalamus.

Monosynaptic Inputs to Ventral Tegmental Area Glutamate and GABA Co-transmitting Neurons.

A unique population of ventral tegmental area (VTA) neurons co-transmits glutamate and GABA. However, the circuit inputs to VTA VGluT2+VGaT+ neurons are unknown, limiting our understanding of their functional capabilities. By coupling monosynaptic rabies tracing with intersectional genetic targeting in male and female mice, we found that VTA VGluT2+VGaT+ neurons received diverse brainwide inputs. The largest numbers of monosynaptic inputs to VTA VGluT2+VGaT+ neurons were from superior colliculus (SC), lateral hypothalamus (LH), midbrain reticular nucleus, and periaqueductal gray, whereas the densest inputs relative to brain region volume were from the dorsal raphe nucleus, lateral habenula, and VTA. Based on these and prior data, we hypothesized that LH and SC inputs were from glutamatergic neurons. Optical activation of glutamatergic LH neurons activated VTA VGluT2+VGaT+ neurons regardless of stimulation frequency and resulted in flee-like ambulatory behavior. In contrast, optical activation of glutamatergic SC neurons activated VTA VGluT2+VGaT+ neurons for a brief period of time at high frequency and resulted in head rotation and arrested ambulatory behavior (freezing). Stimulation of glutamatergic LH neurons, but not glutamatergic SC neurons, was associated with VTA VGluT2+VGaT+ footshock-induced activity and inhibition of LH glutamatergic neurons disrupted VTA VGluT2+VGaT+ tailshock-induced activity. We interpret these results such that inputs to VTA VGluT2+VGaT+ neurons may integrate diverse signals related to the detection and processing of motivationally salient outcomes.

Increased forebrain EAAT3 expression confers resilience to chronic stress.

Depression is a disabling and highly prevalent psychiatric illness. Multiple studies have linked glutamatergic dysfunction with the pathophysiology of depression, but the exact alterations in the glutamatergic system that contribute to depressive-like behaviors are not fully understood. Recent evidence suggests that a decreased level in neuronal glutamate transporter (EAAT3), known to control glutamate levels and limit the activation of glutamate receptors at synaptic sites, may contribute to the manifestation of a depressive phenotype. Here, we tested the possibility that increased EAAT3 expression at excitatory synapses could reduce the susceptibility of mice to develop depressive-like behaviors when challenged to a 5-week unpredictable chronic mild stress (UCMS) protocol. Mice overexpressing EAAT3 in the forebrain (EAAT3glo/CMKII) and control littermates (EAAT3glo) were assessed for depressive-like behaviors and long-term memory performance after being subjected to UCMS conditions. We found that, after UCMS, EAAT3glo/CMKII mice did not exhibit depressive-like behaviors or memory alterations observed in control mice. Moreover, we found that EAAT3glo/CMKII mice did not show alterations in phasic dopamine release in the nucleus accumbens neither in long-term synaptic plasticity in the CA1 region of the hippocampus after UCMS, as observed in control littermates. Altogether these results suggest that forebrain EAAT3 overexpression may be related to a resilient phenotype, both at behavioral and functional level, to the deleterious effect of chronic stress, highlighting the importance of neuronal EAAT3 in the pathophysiology of depressive-like behaviors.

Hunger signalling in the olfactory bulb primes exploration, food-seeking and peripheral metabolism

ObjectiveAlthough the metabolic state of an organism affects olfactory function, the precise mechanisms and their impact on behavior and metabolism remain unknown. Here, we assess whether ghrelin receptors (GHSRs) in the olfactory bulb (OB) increase olfactory function and influence foraging behaviors and metabolism. MethodsWe performed a detailed behavioural and metabolic analysis in mice lacking GHSRs in the OB (OBGHSR deletion). We also analsyed OB scRNA-seq and spatial transcriptomic datasets to assess GHSR+ cells in the main and accessory olfactory bulbs, as well as the anterior olfactory nucleus. ResultsOBGHSR deletion affected olfactory discrimination and habituation to both food and non-food odors. Anxiety-like and depression-like behaviors were significantly greater after OBGHSR deletion, whereas exploratory behavior was reduced, with the greatest effect under fasted conditions. OBGHSR deletion impacted feeding behavior as evidenced by altered bout number and duration, as well as buried food-seeking. OBGHSR deletion increased body weight and fat mass, spared fat utilisation on a chow diet and impaired glucose metabolism indicating metabolic dysfunction. Cross referenced analysis of OB scRNA-seq and spatial transcriptomic datasets revealed GHSR+ glutamate neurons in the main and accessory olfactory bulbs, as well as the anterior olfactory nucleus. Ablation of glutamate neurons in the OB reduced ghrelin-induced food finding and phenocopied results seen after OBGHSR deletion. ConclusionsOBGHSRs help to maintain olfactory function, particularly during hunger, and facilitate behavioral adaptations that optimise food-seeking in anxiogenic environments, priming metabolic pathways in preparation for food consumption.

Glutamate uptake is transiently compromised in the perilesional cortex following controlled cortical impact.

Glutamate, the primary excitatory neurotransmitter in the CNS, is regulated by the excitatory amino acid transporters (EAATs) GLT-1 and GLAST. Following traumatic brain injury (TBI), extracellular glutamate levels increase, contributing to excitotoxicity, circuit dysfunction, and morbidity. Increased neuronal glutamate release and compromised astrocyte-mediated uptake contribute to elevated glutamate, but the mechanistic and spatiotemporal underpinnings of these changes are not well established. Using the controlled cortical impact (CCI) model of TBI and iGluSnFR glutamate imaging, we quantified extracellular glutamate dynamics after injury. Three days post-injury, glutamate release was increased, and glutamate uptake and GLT-1 expression were reduced. 7- and 14-days post-injury, glutamate dynamics were comparable between sham and CCI animals. Changes in peak glutamate response were unique to specific cortical layers and proximity to injury. This was likely driven by increases in glutamate release, which was spatially heterogenous, rather than reduced uptake, which was spatially uniform. The astrocyte K + channel, Kir4.1, regulates activity-dependent slowing of glutamate uptake. Surprisingly, Kir4.1 was unchanged after CCI and accordingly, activity-dependent slowing of glutamate uptake was unaltered. This dynamic glutamate dysregulation after TBI underscores a brief period in which disrupted glutamate uptake may contribute to dysfunction and highlights a potential therapeutic window to restore glutamate homeostasis.

The SWELL1 Channel Promotes Ischemic Brain Damage by Mediating Neuronal Swelling and Glutamate Toxicity.

Cytotoxic neuronal swelling and glutamate excitotoxicity are two hallmarks of ischemic stroke. However, the underlying molecular mechanisms are not well understood. Here, it is reported that SWELL1, the essential subunit of the volume-regulated anion channel (VRAC), plays a dual role in ischemic injury by promoting neuronal swelling and glutamate excitotoxicity. SWELL1 expression is upregulated in neurons and astrocytes after experimental stroke in mice. The neuronal SWELL1 channel is activated by intracellular hypertonicity, leading to Cl- influx-dependent cytotoxic neuronal swelling and subsequent cell death. Additionally, the SWELL1 channel in astrocytes mediates pathological glutamate release, indicated by increases in neuronal slow inward current frequency and tonic NMDAR current. Pharmacologically, targeting VRAC with a new inhibitor, an FDA-approved drug Dicumarol, attenuated cytotoxic neuronal swelling and cell death, reduced astrocytic glutamate release, and provided significant neuroprotection in mice when administered either before or after ischemia. Therefore, these findings uncover the pleiotropic effects of the SWELL1 channel in neurons and astrocytes in the pathogenesis of ischemic stroke and provide proof of concept for therapeutically targeting it in this disease.

Corticotropin-releasing factor and GABA in the ventral tegmental area modulate partner preference formation in male and female prairie voles (Microtus ochrogaster).

The mesolimbic reward system is associated with the promotion and rewarding benefits of social relationships. In the socially monogamous prairie vole (Microtus ochrogaster), the establishment of a pair bond can be displayed by a robust preference for a breeding partner and aggressive rejection of unfamiliar conspecifics. Mesolimbic dopamine signaling influences bond-related behaviors within the vole through dopamine transmission and receptor activity in the nucleus accumbens. However, only one experiment has examined how the ventral tegmental area (VTA), a region that produces much of the fore- and mid-brain dopamine, regulates these social behaviors. Specifically, inhibition of either glutamate or GABA neurons in the VTA during a brief courtship promoted a partner preference formation in male prairie voles. The VTA is a heterogeneous structure that contains dopamine, GABA, and glutamate neurons as well as receives a variety of projections including corticotropin-releasing factor (CRF) suggested to modulate dopamine release. We used pharmacological manipulation to examine how GABA and CRF signaling in the VTA modulate partner preference formation in male and female prairie voles. Specifically, we used a 3 h partner preference test, a social choice test, to assess the formation of a partner preference following an infused bicuculline and CRF during a 1 h cohabitation and muscimol and CP154526, a CRFR1 antagonist, during a 24 h cohabitation with an opposite-sex conspecific. Our study demonstrated that bicuculline, a GABA A receptor antagonist, and CRF in the VTA promoted a partner preference, whereas low-dose muscimol, a GABA A receptor agonist, and CP154526, a CRFR1 antagonist, inhibited a partner preference in both male and female prairie voles. This study demonstrated that GABA and CRF inputs into the VTA is necessary for the formation of a partner preference in male and female prairie voles.

Shared patterns of glial transcriptional dysregulation link Huntington's disease and schizophrenia.

Huntington's disease and juvenile-onset schizophrenia have long been regarded as distinct disorders. However, both manifest cell-intrinsic abnormalities in glial differentiation, with resultant astrocytic dysfunction and hypomyelination. To assess whether a common mechanism might underlie the similar glial pathology of these otherwise disparate conditions, we used comparative correlation network approaches to analyse RNA-sequencing data from human glial progenitor cells (hGPCs) produced from disease-derived pluripotent stem cells. We identified gene sets preserved between Huntington's disease and schizophrenia hGPCs yet distinct from normal controls that included 174 highly connected genes in the shared disease-associated network, focusing on genes involved in synaptic signalling. These synaptic genes were largely suppressed in both schizophrenia and Huntington's disease hGPCs, and gene regulatory network analysis identified a core set of upstream regulators of this network, of which OLIG2 and TCF7L2 were prominent. Among their downstream targets, ADGRL3, a modulator of glutamatergic synapses, was notably suppressed in both schizophrenia and Huntington's disease hGPCs. Chromatin immunoprecipitation sequencing confirmed that OLIG2 and TCF7L2 each bound to the regulatory region of ADGRL3, whose expression was then rescued by lentiviral overexpression of these transcription factors. These data suggest that the disease-associated suppression of OLIG2 and TCF7L2-dependent transcription of glutamate signalling regulators may impair glial receptivity to neuronal glutamate. The consequent loss of activity-dependent mobilization of hGPCs may yield deficient oligodendrocyte production, and hence the hypomyelination noted in these disorders, as well as the disrupted astrocytic differentiation and attendant synaptic dysfunction associated with each. Together, these data highlight the importance of convergent glial molecular pathology in both the pathogenesis and phenotypic similarities of two otherwise unrelated disorders, Huntington's disease and schizophrenia.

β-amyloid monomer scavenging by an anticalin protein prevents neuronal hyperactivity in mouse models of Alzheimer’s Disease

Hyperactivity mediated by synaptotoxic β-amyloid (Aβ) oligomers is one of the earliest forms of neuronal dysfunction in Alzheimer’s disease. In the search for a preventive treatment strategy, we tested the effect of scavenging Aβ peptides before Aβ plaque formation. Using in vivo two-photon calcium imaging and SF-iGluSnFR-based glutamate imaging in hippocampal slices, we demonstrate that an Aβ binding anticalin protein (Aβ-anticalin) can suppress early neuronal hyperactivity and synaptic glutamate accumulation in the APP23xPS45 mouse model of β-amyloidosis. Our results suggest that the sole targeting of Aβ monomers is sufficient for the hyperactivity-suppressing effect of the Aβ-anticalin at early disease stages. Biochemical and neurophysiological analyses indicate that the Aβ-anticalin-dependent depletion of naturally secreted Aβ monomers interrupts their aggregation to neurotoxic oligomers and, thereby, reverses early neuronal and synaptic dysfunctions. Thus, our results suggest that Aβ monomer scavenging plays a key role in the repair of neuronal function at early stages of AD.

Expression of mGluR5 in Pediatric Hodgkin and Non-Hodgkin lymphoma-A Comparative Analysis of Immunohistochemical and Clinical Findings Regarding the Association between Tumor and Paraneoplastic Neurological Disease.

Autoantibodies targeting the neuronal antigen metabotropic glutamate receptor 5 (mGluR5) have been identified in patients with Ophelia syndrome, which describes a co-occurrence of paraneoplastic limbic encephalitis and Hodgkin lymphoma (HL). Little data exist regarding frequency and function of mGluR5 in HL and its potential role in causing seropositive paraneoplastic disease. We studied a representative cohort of pediatric HL and NHL patients (n = 57) using immunohistochemistry and fluorescence staining to investigate mGluR5 expression. All lymphoma tissues displayed positive mGluR5 staining, with focus on Hodgkin-Reed-Sternberg (H-RS) cells. We did not detect any mGluR5 staining in tumor-free lymph nodes, which is consistent with the absence of GRM5 transcripts in RNA-sequencing data from non-malignant B and T cells. The frequent presence in pediatric lymphoma falls in line with reports of mGluR5 expression and associated tumor progression in other malignancies. We tested for correlation with clinical features, focusing on disease progression and neurological symptoms. Low mGluR5 expression in H-RS cells correlated with young patient age (<15 years) and positive histology for EBV infection. Paraneoplastic or neurological symptoms were found exclusively in HL patients. While an impact of mGluR5 on HL severity remains possible, a prognostic value of mGluR5 expression levels requires further investigation.

VTA glutamatergic projections to the nucleus accumbens suppress psychostimulant-seeking behavior

Converging evidence indicates that both dopamine and glutamate neurotransmission within the nucleus accumbens (NAc) play a role in psychostimulant self-administration and relapse in rodent models. Increased NAc dopamine release from ventral tegmental area (VTA) inputs is critical to psychostimulant self-administration and NAc glutamate release from prelimbic prefrontal cortex (PFC) inputs synapsing on medium spiny neurons (MSNs) is critical to reinstatement of psychostimulant-seeking after extinction. The regulation of the activity of MSNs by VTA dopamine inputs has been extensively studied, and recent findings have demonstrated that VTA glutamate neurons target the NAc medial shell. Here, we determined whether the mesoaccumbal glutamatergic pathway plays a role in psychostimulant conditioned place preference and self-administration in mice. We used optogenetics to induce NAc release of glutamate from VTA inputs during the acquisition, expression, and reinstatement phases of cocaine- or methamphetamine-induced conditioned place preference (CPP), and during priming-induced reinstatement of cocaine-seeking behavior. We found that NAc medial shell release of glutamate resulting from the activation of VTA glutamatergic fibers did not affect the acquisition of cocaine-induced CPP, but it blocked the expression, stress- and priming-induced reinstatement of cocaine- and methamphetamine CPP, as well as it blocked the priming-induced reinstatement of cocaine-seeking behavior after extinction. These findings indicate that in contrast to the well-recognized mesoaccumbal dopamine system that is critical to psychostimulant reward and relapse, there is a parallel mesoaccumbal glutamatergic system that suppresses reward and psychostimulant-seeking behavior.

Saikosaponin antidepressant mechanism: Improving the sphingolipid metabolism in the cortex via Apolipoprotein E and triggering neurovascular coupling

BackgroundSince the pathogenesis of depression is complex, antidepressant therapy remains unsatisfactory. Recent evidence suggests a link between depression and lipid metabolism. Saikosaponin (SS) exhibits antidepression and lipid-regulating effects in modern pharmacology. However, it is unknown whether lipid regulation is the key mechanism of the SS antidepressant effect and how it works. PurposeIn this study, we investigated the relationship between the antidepressant activity of SS and the regulation of lipid metabolism and explored potential mechanisms. MethodsAPOE-/- mice, in combination with the chronic unpredictable mild stress (CUMS) model, were used to study the relationship between SS antidepressant activity and lipid metabolism through behavioral, electrophysiological techniques, and non-targeted lipidomics. Western blot, primary cell culture technology, and laser speckle cerebral blood flow imaging were employed to elucidate potential mechanisms. GraphPad Prism was used for statistical analysis, and p < 0.05 was considered statistically significant. ResultsAPOE-/- mice exhibit more severe depressive-like behavior and dysregulation of sphingolipid metabolism in CUMS. SS alleviates depressive behavior and cortical sphingolipid metabolism disorder caused by CUMS, but has no effect on APOE-/- mice. SS alleviates the imbalance between ceramide (Cer) and sphingomyelin (SM) through acidic sphingomyelinase (AMSase). In addition, SS regulates neuronal glutamate release via sphingolipid metabolism, thereby alleviating the CUMS-induced inhibition of neurovascular coupling (regulates metabotropic glutamate receptor and IP3 receptor), which ameliorates the reduction of cerebral blood flow in depressed mice. ConclusionOur study highlights the role of lipid metabolism in the antidepressant activity of SS and explores its underlying mechanisms. This study provided new insights into the better understanding of the antidepressant mechanisms of phytomedicine while increasing the possibility of lipid metabolism as a therapeutic strategy for depression.

Single nuclei RNA-seq reveals a medium spiny neuron glutamate excitotoxicity signature prior to the onset of neuronal death in an ovine Huntington's disease model.

Huntington's disease (HD) is a neurodegenerative genetic disorder caused by an expansion in the CAG repeat tract of the huntingtin (HTT) gene resulting in behavioural, cognitive, and motor defects. Current knowledge of disease pathogenesis remains incomplete, and no disease course-modifying interventions are in clinical use. We have previously reported the development and characterisation of the OVT73 transgenic sheep model of HD. The 73 polyglutamine repeat is somatically stable and therefore likely captures a prodromal phase of the disease with an absence of motor symptomatology even at 5-years of age and no detectable striatal cell loss. To better understand the disease-initiating events we have undertaken a single nuclei transcriptome study of the striatum of an extensively studied cohort of 5-year-old OVT73 HD sheep and age matched wild-type controls. We have identified transcriptional upregulation of genes encoding N-methyl-D-aspartate (NMDA), α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and kainate receptors in medium spiny neurons, the cell type preferentially lost early in HD. Further, we observed an upregulation of astrocytic glutamate uptake transporters and medium spiny neuron GABAA receptors, which may maintain glutamate homeostasis. Taken together, these observations support the glutamate excitotoxicity hypothesis as an early neurodegeneration cascade-initiating process but the threshold of toxicity may be regulated by several protective mechanisms. Addressing this biochemical defect early may prevent neuronal loss and avoid the more complex secondary consequences precipitated by cell death.

Ventral pallidum GABA and glutamate neurons drive approach and avoidance through distinct modulation of VTA cell types.

The ventral pallidum (VP) contains GABA and glutamate neurons projecting to ventral tegmental area (VTA) whose stimulation drives approach and avoidance, respectively. Yet little is known about the mechanisms by which VP cell types shape VTA activity and drive behavior. Here, we found that both VP GABA and glutamate neurons were activated during approach to reward or by delivery of an aversive stimulus. Stimulation of VP GABA neurons inhibited VTA GABA, but activated dopamine and glutamate neurons. Remarkably, stimulation-evoked activation was behavior-contingent such that VTA recruitment was inhibited when evoked by the subject's own action. Conversely, VP glutamate neurons activated VTA GABA, as well as dopamine and glutamate neurons, despite driving aversion. However, VP glutamate neurons evoked dopamine in aversion-associated ventromedial nucleus accumbens (NAc), but reduced dopamine releasein reward-associated dorsomedial NAc. These findings show how heterogeneous VP projections to VTA can be engaged to shape approach and avoidance behaviors.

Gypenoside XVII Reduces Synaptic Glutamate Release and Protects against Excitotoxic Injury in Rats.

Excitotoxicity is a common pathological process in neurological diseases caused by excess glutamate. The purpose of this study was to evaluate the effect of gypenoside XVII (GP-17), a gypenoside monomer, on the glutamatergic system. In vitro, in rat cortical nerve terminals (synaptosomes), GP-17 dose-dependently decreased glutamate release with an IC50 value of 16 μM. The removal of extracellular Ca2+ or blockade of N-and P/Q-type Ca2+ channels and protein kinase A (PKA) abolished the inhibitory effect of GP-17 on glutamate release from cortical synaptosomes. GP-17 also significantly reduced the phosphorylation of PKA, SNAP-25, and synapsin I in cortical synaptosomes. In an in vivo rat model of glutamate excitotoxicity induced by kainic acid (KA), GP-17 pretreatment significantly prevented seizures and rescued neuronal cell injury and glutamate elevation in the cortex. GP-17 pretreatment decreased the expression levels of sodium-coupled neutral amino acid transporter 1, glutamate synthesis enzyme glutaminase and vesicular glutamate transporter 1 but increased the expression level of glutamate metabolism enzyme glutamate dehydrogenase in the cortex of KA-treated rats. In addition, the KA-induced alterations in the N-methyl-D-aspartate receptor subunits GluN2A and GluN2B in the cortex were prevented by GP-17 pretreatment. GP-17 also prevented the KA-induced decrease in cerebral blood flow and arginase II expression. These results suggest that (i) GP-17, through the suppression of N- and P/Q-type Ca2+ channels and consequent PKA-mediated SNAP-25 and synapsin I phosphorylation, reduces glutamate exocytosis from cortical synaptosomes; and (ii) GP-17 has a neuroprotective effect on KA-induced glutamate excitotoxicity in rats through regulating synaptic glutamate release and cerebral blood flow.

Synaptic Profile and Oxidative Stress Associated with Amyloid-β in the Hippocampus

Alzheimer’s Disease (AD) is a neurodegenerative disorder that leads to cognitive decline and memory loss. The neuropathology is mainly due to disturbances in neuronal circuits and protein aggregations of phosphorylated tau and Amyloid-β (Aβ). Other factors found in disease progression are oxidative stress, microglial activation, and decreased synaptic transmission. However, it is unknown whether these changes occur only in close association with Aβ plaques, or rather have broad occurrence throughout memory-related brain structures. Thus, we analyzed synaptic markers, glial cells, and oxidative stress in the memory associated CA1 hippocampal region of APP/PS1 transgenic mice. Specifically, we assessed these targets in the immediate vicinity and distant from Aβ plaques. Hippocampal sections (coronal, 30 μm thick) from 1-year-old APP/PS1 mice and their wild type controls (n = 6/group) were fluorescently labeled for synapse density (synaptophysin), vesicular glutamate transporter (vGLUT2), DNA oxidation (8-hydroxyguanosine, 8-OHG), microglia (Iba-1), astrocytes (GFAP), neurons (NeuN), and Aβ plaques (X-34). Images were taken in the CA1 region with a conventional fluorescent microscope and analyzed using ImageJ. Fluorescence intensity was then quantified for each group. Next, the intensity profile was plotted for each fluorophore across the width of the Aβ plaques. There were relatively few amyloid plaques in the hippocampal CA1 region of APP/PS1 mice when compared to other regions of the hippocampus and cerebral cortex. Within the CA1 region, and in absence of Aβ, there was no pronounced change in synaptic density, presynaptic glutamate transporters, neurons, DNA oxidation, astrocytes, or microglia when compared to wild-type control. However, fluorescent intensity of some targets changed markedly along the perimeter of occasionally occurring Aβ plaques in the CA1 region. While the intensity profile of synaptophysin declined gradually towards the center of Aβ plaques, oxidative stress and microglia increased in the immediate surroundings of Aβ. Unexpectedly, also the intensity of presynaptic glutamate transporter vGLUT2 increased towards the core of the Aβ plaque. In summary, our data showed increased vesicular glutamate transporter, microglia, and oxidative stress confined to the vicinity of Aβ plaques in APP/PS1 mice. Increased vGLUT2 levels due to Aβ have been previously associated with hyperexcitability in AD. The parallel or subsequent decrease in synaptophysin is viewed as a compensatory response to limit hyperactivity. Together, the present study reveals important insights about the dynamics of cellular components in the vicinity of Aβ, and that aggregates of Aβ differentially affect presynaptic components important for synaptic transmission. NIH R15AG065927 (TDO &amp; DO), Truman State GIASR grant (TS). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Transcriptional signatures of fentanyl use in the mouse ventral tegmental area.

Synthetic opioids such as fentanyl contribute to the vast majority of opioid-related overdose deaths, but fentanyl use remains broadly understudied. Like other substances with misuse potential, opioids cause lasting molecular adaptations to brain reward circuits, including neurons in the ventral tegmental area (VTA). The VTA contains numerous cell types that play diverse roles in opioid use and relapse; however, it is unknown how fentanyl experience alters the transcriptional landscape in specific subtypes. Here, we performed single nuclei RNA sequencing to study transcriptional programs in fentanyl-experienced mice. Male and female C57/BL6 mice self-administered intravenous fentanyl (1.5μg/kg/infusion) or saline for 10days. After 24 h abstinence, VTA nuclei were isolated and prepared for sequencing on the 10× platform. We identified different patterns of gene expression across cell types. In dopamine neurons, we found enrichment of genes involved in growth hormone signalling. In dopamine-glutamate-GABA combinatorial neurons, and some GABA neurons, we found enrichment of genes involved in Pi3k-Akt signalling. In glutamate neurons, we found enrichment of genes involved in cholinergic signalling. We identified transcriptional regulators for the differentially expressed genes in each neuron cluster, including downregulated transcriptional repressor Bcl6, and upregulated transcription factor Tcf4. We also compared the fentanyl-induced gene expression changes identified in mouse VTA with a published rat dataset in bulk VTA, and found overlap in genes related to GABAergic signalling and extracellular matrix interaction. Together, we provide a comprehensive picture of how fentanyl self-administration alters the transcriptional landscape of the mouse VTA that serves as the foundation for future mechanistic studies.

Regulation of Feeding Behavior by Optogenetic Activation of Inputs to Lateral Hypothalamus

The bed nucleus stria terminalis (BNST) and parabrachial nucleus (PBN) are two brain regions in correspondence with the lateral hypothalamic area (LHA) that are responsible for regulating feeding behavior in mice. It is acknowledged that increasing the activity of GABAergic BNST inputs (which release the inhibitory neurotransmitter GABA) to the LHA inhibits LHA glutamate neurons and increases feeding, whereas increasing activity of glutamatergic PBN inputs (which release the excitatory neurotransmitter glutamate) to the LHA excites local glutamate neurons and decreases feeding. Obesity is a prevalent problem in our society, and therefore it is important to understand the reasons behind excessive food intake habits of humans. To address this issue, we tested for effects of activating the BNST-LHA and PBN-LHA pathways in relation to the satiety state of the mice. We stimulated the BNST and PBN inputs to LHA in fasted and fed mice. We tested the effects of Satiety State (fed vs. fasted) and stimulation Frequency (5-40 Hz) on sucrose seeking behavior of two Groups of mice (ChR2 vs YFP controls). The BNST-LHA pathway tended to show a general increase in feeding behaviors, while the PBN-LHA pathway did not show a significant effect of activation. From these results, further studies can be conducted to explore more about these neural pathways and the mechanisms underlying feeding behaviors. On a broader scale, these findings can inform future therapeutics that could help prevent unhealthy eating habits and obesity.

Maternal treatment with a selective delta-opioid receptor agonist during gestation has a sex-specific pro-cognitive action in offspring: mechanisms involved.

Background: There is growing evidence that the treatment of several mental disorders can potentially benefit from activation of delta-opioid receptors. In the future, delta-agonists with a safe pharmacological profile can be used for the treatment of mood disorders in pregnant women. However, the data on prenatal exposure to delta-opioid agonists are missing. The present study is aimed to test the hypothesis that the activation of delta-opioid receptors during gravidity has positive effects on the behaviour accompanied by changes in glutamate and monoamine neurotransmission. Methods: Gestating Wistar rats were chronically treated with a selective delta-agonist SNC80 or vehicle. Adult male and female offspring underwent novel object recognition (for the assessment of cognition) and open field (for the assessment of anxiety and habituation) tests, followed by in vivo electrophysiological examination of the activity of hippocampal glutamate and midbrain serotonin (5-HT) and dopamine neurons. Results: We found that the maternal treatment with SNC80 did not affect the offspring's anxiety, habituation, and 5-HT neuronal firing activity. Female offspring of SNC80-treated dams exhibited improved novelty recognition associated with decreased firing rate and burst activity of glutamate and dopamine neurons. Conclusion: Maternal treatment with delta-opioid agonists during gestation may have a pro-cognitive effect on offspring without any negative effects on anxiety and habituation. The putative pro-cognitive effect might be mediated via mechanism(s) involving the firing activity of hippocampal glutamate and mesolimbic dopamine neurons.

Adolescent Stress-Induced Ventral Hippocampus Redox Dysregulation Underlies Behavioral Deficits and Excitatory/Inhibitory Imbalance Related to Schizophrenia.

Redox dysregulation has been proposed as a convergent point of childhood trauma and the emergence of psychiatric disorders, such as schizophrenia (SCZ). A critical region particularly vulnerable to environmental insults during adolescence is the ventral hippocampus (vHip). However, the impact of severe stress on vHip redox states and their functional consequences, including behavioral and electrophysiological changes related to SCZ, are not entirely understood. After exposing adolescent animals to physical stress (postnatal day, PND31-40), we explored social and cognitive behaviors (PND47-49), the basal activity of pyramidal glutamate neurons, the number of parvalbumin (PV) interneurons, and the transcriptomic signature of the vHip (PND51). We also evaluated the impact of stress on the redox system, including mitochondrial respiratory function, reactive oxygen species (ROS) production, and glutathione (GSH) levels in the vHip and serum. Adolescent-stressed animals exhibited loss of sociability, cognitive impairment, and vHip excitatory/inhibitory (E/I) imbalance. Genome-wide transcriptional profiling unveiled the impact of stress on redox system- and synaptic-related genes. Stress impacted mitochondrial respiratory function and changes in ROS levels in the vHip. GSH and glutathione disulfide (GSSG) levels were elevated in the serum of stressed animals, while GSSG was also increased in the vHip and negatively correlated with sociability. Additionally, PV interneuron deficits in the vHip caused by adolescent stress were associated with oxidative stress. Our results highlight the negative impact of adolescent stress on vHip redox regulation and mitochondrial function, which are partially associated with E/I imbalance and behavioral abnormalities related to SCZ.