NMDA Receptor Expression Research Articles

Long-term effects of a double hit murine model for schizophrenia on parvalbumin expressing cells and plasticity-related molecules in the thalamic reticular nucleus and the habenula

The exposure to aversive experiences during early-life affects brain maturation and induces changes in behavior. Additionally, when these experiences coincide with subtle neurodevelopmental alterations, they may contribute to the emergence of psychiatric disorders, such as schizophrenia. Studies in patients and animal models have identified changes in parvalbumin (PV) expressing inhibitory neurons, highlighting their significance in the etiology of this disorder. Most studies have been focused on the cortex, but PV+ neurons also provide inhibitory input to diencephalic regions, particularly to the thalamus (through cells in the thalamic reticular nucleus, TRN) and the habenula. Remarkably, alterations in both nuclei have been described in schizophrenia. Some of these changes in PV+ cells may be mediated by perineuronal nets (PNN), specialized regions of the extracellular matrix that often surround them and regulate their synaptic input and activity. Interestingly, the physiological maturation and integration of PV+ neurons, which involves the assembly of PNN, occurs during early postnatal life. Plasticity molecules associated to inhibitory neurons, such as PSA-NCAM, or NMDA receptors (NMDAR) can also influence the structure and function of these cells. Growing evidence also indicates that glial cells regulate the physiology of PV+ neurons by influencing their maturation and modulating their synaptic connectivity. To explore the impact of early-life aversive experiences and concomitant subtle neurodevelopmental alterations on diencephalic PV+ cells, we analyzed adult male mice subjected to a double-hit model (DHM) of schizophrenia, combining a single injection of an NMDAR antagonist at P7 and post-weaning social isolation. We observed that exploratory behavior, PV+ neurons and their associated PNN, as well as PSA-NCAM and NMDAR expression and glial cells, in the TRN and the habenula were affected by the DHM or one of its factors. To our knowledge, this is the first report on such alterations in these diencephalic structures in an animal model combining neurodevelopmental alterations and early-life stress during adolescence. Our findings complement previous work on PV+ neurons in cortical regions and underscore the importance of studying diencephalic inhibitory networks and their intricate interactions with aversive experiences and neurodevelopmental alterations during early life in the context of schizophrenia.

Whole Nervous System Expression of Glutamate Receptors Reveals Distinct Receptor Roles in Sensorimotor Circuits.

The goal of connectomics is to reveal the links between neural circuits and behavior. Larvae of the primitive chordate Ciona are well-suited to make contributions in this area. In addition to having a described connectome, Ciona larvae have a range of readily quantified behaviors. Moreover, the small number of neurons in the larval CNS (∼180) holds the promise of a comprehensive characterization of individual neurons. We present single-neuron predictions for glutamate receptor (GlutR) expression based on in situ hybridization. Included are both ionotropic receptors (AMPA, NMDA, and kainate) and metabotropic receptors. The predicted glutamate receptor expression dataset is discussed in the context of known circuits driving behaviors such as phototaxis, mechanosensation, and looming shadow response. The predicted expression of AMPA and NMDA receptors may help resolve issues regarding the co-production of GABA and glutamate by a subset of photoreceptors. The targets of these photoreceptors in the midbrain appear to express NMDA receptors, but not AMPA receptors. This is in agreement with previous results indicating that GABA is the primary neurotransmitter from the photoreceptors evoking a swimming response through a disinhibition mechanism and that glutamate may, therefore, have only a modulatory action in this circuit. Other findings reported here are more unexpected. For example, many of the targets of glutamatergic epidermal sensory neurons (ESNs) do not express any of the ionotropic receptors, yet the ESNs themselves express metabotropic receptors. Thus, we speculate that their production of glutamate may be for communication with neighboring ESNs, rather than to their interneuron targets.

Memantine attenuates the development of osteoarthritis by blocking NMDA receptor mediated calcium overload and chondrocyte senescence

BackgroundMemantine, which is an FDA-proven drug for the treatment of dementia, exerts its function by blocking the function of NMDA (N-methyl-D-aspartate) receptor, a calcium-permeable ion channel that reduces cytotoxic calcium overload. Chondrocyte senescence is a crucial cellular event that contributes to articular cartilage degeneration during osteoarthritis (OA) development. To date, the effects of memantine and its downstream NMDA receptor on chondrocyte senescence and OA have been rarely reported. MethodsThe protein levels of NMDA receptor and its agonistic ligand, glutamate, were compared between normal and OA chondrocytes. The quantity of intracellular calcium ions and the level of mitochondrial damage were evaluated using specific fluorescent probes and transmission electron microscopy (TEM), respectively. Chondrocyte senescence was evaluated by senescence-associated β-galactosidase (SA-β-Gal) staining and p16INK4a analysis. The function of NMDA receptor in chondrocyte senescence and OA was tested via agonists activation and gene knockdown experiments. The therapeutic effects of memantine on OA were examined both in vitro and in vivo. Additionally, to verify the findings from animal samples, a propensity score-matched cohort study was conducted using data from a United Kingdom primary care database (i.e., IQVIA Medical Research Database [IMRD]) to compare the risk of OA-related joint replacement involved in memantine initiators versus active comparators (i.e., acetylcholinesterase [AchE] initiators) in patients with dementia. ResultsThe protein expression of NMDA receptor and the secretion of glutamate were both significantly increased in OA chondrocytes. NMDA receptor activation was found to stimulate chondrocyte calcium overload, which further led to mitochondrial fragmentation and chondrocyte senescence. Blocking the NMDA receptor with memantine and N-methyl-D-aspartate receptor subunit 1(NR1, the gene encoding NMDA receptor) knockdown resulted in reduced calcium influx, mitochondrial fragmentation, as well as cellular senescence in OA chondrocytes. Intra-articular injection of memantine in OA mice also exhibited protective effects against cartilage degeneration. Moreover, in the 1:5 propensity score-matched cohort study consisting of 6218 patients (n = 1435 in the memantine cohort; n = 4783 in the AchE cohort), the memantine initiator was associated with a lower risk of OA-related joint replacement than AchE initiators (Hazard ratio = 0.56, 95 % confidence interval: 0.34 to 0.99). ConclusionNMDA receptor plays an important role in inflammatory-induced cytotoxic calcium overload in chondrocytes, while memantine can effectively block the NMDA receptor to reduce chondrocyte senescence and retard the development of OA. The translational potential of this articleAs a clinically licensed drug used for the treatment of dementia, memantine has shown promising therapeutic effects on OA. Mechanistically, it functions by blocking NMDA receptor from mediating chondrocyte senescence. The protective effects of memantine against OA were verified not only by in vivo and in vitro experiments but also via a propensity score-matched human cohort study. These findings presented robust evidence for repurposing memantine for the treatment of OA.

BNST GluN2D-containing NMDARs contribute to ethanol intake but not negative affective behaviors in female mice.

Alcohol use disorder (AUD) is a chronic, relapsing disease, highly comorbid with anxiety and depression. The bed nucleus of the stria terminalis (BNST) and Crh+ neurons in this region play a key role in chronic ethanol-induced increases in volitional intake, hypothesized to be driven by emergent negative affective behaviors. Excitatory N-methyl-d-aspartate receptors (NMDARs) are a major target of ethanol, and chronic ethanol exposure has been shown to regulate NMDAR function and expression. Specifically, GluN2D subunit-containing NMDARs have emerged as a target of interest due to their limited distribution and potential roles in affective behavior. Male and female mice underwent a home cage chronic drinking forced abstinence model (CDFA) to assess the impact of 1 day or 2 weeks of ethanol abstinence on BNST synaptic transmission and BNST Grin gene expression. Constitutive and conditional BNST GluN2D knockout mice were used to assess the impact of GluN2D deletion on continuous access ethanol intake as well as negative affect behaviors, using the open field, elevated zero maze, and forced swim tasks. We report here that excitatory transmission undergoes time-dependent upregulation in BNST Crh+ cells. Further, knockdown of dorsal BNST (dBNST) GluN2D expression significantly decreases ethanol intake in female, but not male, mice. While BNST Grin2b expression was significantly increased in protracted abstinence following CDFA, no differences in Grin2d expression were observed in the dBNST or dBNST Crh+ neurons. Finally, we find that deletion of GluN2D fails to alter negative affect in ethanol-naïve female mice. These data suggest a role for BNST GluN2D-containing NMDARs in ethanol drinking but not ethanol abstinence, highlighting sex differences and behavioral specificity. Overall, these data further suggest roles for BNST synaptic signaling in volitional ethanol intake that are partially independent of actions on affective behavior.

Effect of pseudorabies virus infection on NMDA receptor expression in mice and its role in immunosuppression

Pseudorabies virus (PRV), an α-herpesvirus, induces immunosuppression and can lead to severe neurological diseases. N-methyl-D-aspartate receptor (NMDAR), an important excitatory nerve receptor in the central nervous system, is linked to various nervous system pathologies. The link between NMDAR and PRV-induced neurological diseases has not been studied. In vivo studies revealed that PRV infection triggers a reduction in hippocampal NMDAR expression, mediated by inflammatory processes. Extensive hippocampal neuronal degeneration was found in mice on the 6th day by hematoxylin-eosin staining, which was strongly correlated with increased NMDAR protein expression. In vitro studies utilizing the CCK-8 assay demonstrated that treatment with an NMDAR antagonist significantly heightened the cytotoxic effects of PRV on T lymphocytes. Notably, NMDAR inhibition did not affect the replication ability of PRV. However, it facilitated the accumulation of pro-inflammatory cytokines in PRV-infected T cells and enhanced the transcription of the CD25 gene through the secretion of interleukin-2 (IL-2), consequently exacerbating immunosuppression. In this study, we found that NMDAR has functional activity in T lymphocytes and is crucial for the inflammatory and immune responses triggered by PRV infection. These discoveries highlight the significant role of NMDAR in PRV-induced neurological disease pathogenesis.

Efficacy of GluN2B-Containing NMDA receptor antagonist for antitumor and antidepressant therapy in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is the predominant subtype of lung cancer. Evidence suggests that the ionotropic glutamate receptor N-methyl-D-aspartate (NMDA) receptor, a critical molecule in the central nervous system, is expressed in NSCLC. However, the specific expression patterns, subcellular localization, functional modulation, and pathological implications of NMDA receptor subtypes in NSCLC have not been fully elucidated. In this study, we employed a multi-disciplinary approach, combining biochemical and molecular biology with electrophysiological recordings and behavioral assays, to investigate these aspects. We reveal the expression of GluN2B-containing NMDA receptors in A549 and H460 NSCLC cell lines and the induction of NMDA receptor-mediated currents by glutamate in A549 cells. Furthermore, the GluN2B-specific inhibitors ifenprodil and Ro 25–6981 significantly reduced cell viability and migration, while promoting apoptosis. Importantly, intraperitoneal administration of ifenprodil in nude mice inhibited the growth of subcutaneous tumors derived from A549 and H460 cells and ameliorated depression-like behaviors. These findings underscore the potential antiproliferative effects of ifenprodil and Ro 25–6981 and suggest that GluN2B-containing NMDA receptors may represent novel therapeutic targets for NSCLC, with the added benefit of potential antidepressant action.

Gestational valproic acid exposure enhances facial stimulation-evoked cerebellar mossy fiber-granule cell transmission via GluN2A subunit-containing NMDA receptor in offspring mice

Valproic acid (VPA) is one of the most effective antiepileptic drugs, and exposing animals to VPA during gestation has been used as a model for autism spectrum disorder (ASD). Numerous studies have shown that impaired synaptic transmission in the cerebellar cortical circuits is one of the reasons for the social deficits and repetitive behavior seen in ASD. In this study, we investigated the effect of VPA exposure during pregnancy on tactile stimulation-evoked cerebellar mossy fiber-granule cell (MF-GC) synaptic transmission in mice anesthetized with urethane. Three-chamber testing showed that mice exposed to VPA mice exhibited a significant reduction in social interaction compared with the control group. In vivo electrophysiological recordings revealed that a pair of air-puff stimulation on ipsilateral whisker pad evoked MF-GC synaptic transmission, N1, and N2. The evoked MF-GC synaptic responses in VPA-exposed mice exhibited a significant increase in the area under the curve (AUC) of N1 and the amplitude and AUC of N2 compared with untreated mice. Cerebellar surface application of the selective N-methyl-D-aspartate (NMDA) receptor blocker D-APV significantly inhibited facial stimulation-evoked MF-GC synaptic transmission. In the presence of D-APV, there were no significant differences between the AUC of N1 and the amplitude and AUC of N2 in the VPA-exposed mice and those of the untreated mice. Notably, blockade of the GluN2A subunit-containing, but not the GluN2B subunit-containing, NMDA receptor, significantly inhibited MF-GC synaptic transmission and decreased the AUC of N1 and the amplitude and AUC of N2 in VPA-exposed mice to levels similar to those seen in untreated mice. In addition, the GluN2A subunit-containing NMDA receptor was expressed at higher levels in the GC layer of VPA-treated mice than in control mice. These results indicate that gestational VPA exposure in mice produces ASD-like behaviors, accompanied by increased cerebellar MF-GC synaptic transmission and an increase in GluN2A subunit-containing NMDA receptor expression in the offspring.

Trigonelline as an anticonvulsant agent: mechanistic insights into NMDA receptor expression and oxidative stress balance

Glutamatergic neurotransmission and oxidative stress are involved in the pathophysiology of seizures. Some anticonvulsants exert their effects through modulation of these pathways. Trigonelline (TRG) has been shown to possess various pharmacological effects like neuroprotection. Therefore, this study was performed to determine TRG’s anticonvulsant effects, focusing on its potential effects on N-methyl-D-aspartate (NMDA) receptors, a type of glutamate receptor, and oxidative stress state in the prefrontal cortex (PFC) in PTZ-induced seizure in mice. Seventy-two male mice were randomly divided into nine groups. The groups included mice that received normal saline, TRG at doses of 10, 50, and 100 mg/kg, diazepam, NMDA (an agonist), ketamine (an antagonist), the effective dose of TRG with NMDA, as well as sub-effective dose of TRG with ketamine, respectively. All agents were administrated intraperitoneally 60 min before induction of seizures by PTZ. Latency to seizure, total antioxidant capacity (TAC), and malondialdehyde (MDA) levels in serum and PFC were measured. Furthermore, the gene expression of NR2A and NR2B, subunits of NMDA receptors, was measured in the PFC. TRG administration increased the latency to seizure onset and enhanced TAC while reducing MDA levels in both the PFC and serum. TRG also decreased the gene expression of NR2B in the PFC. Unexpectedly, the findings revealed that the concurrent administration of ketamine amplified, whereas NMDA mitigated, the impact of TRG on latency to seizure. Furthermore, NMDA diminished the positive effects of TRG on antioxidant capacity and oxidative stress, while ketamine amplified these beneficial effects, indicating a complex interaction between TRG and NMDA receptor modulation. In the gene expression of NMDA receptors, results showed that ketamine significantly decreased the gene expression of NR2B when co-administrated with a sub-effective dose of TRG. It was found that, at least partially, the anticonvulsant effect of TRG in PTZ-induced seizures in male mice was mediated by the attenuation of glutamatergic neurotransmission as well as the reduction of oxidative stress.

Involvement of γ-Aminobutyric acid and N-methyl-D-aspartate receptors in diabetic gastropathy in rats: possible beneficial effect of prolonged treatment with insulin and magnesium supplement

Gastrointestinal dysfunction is a severe and common complication in diabetic patients. Some evidence shows that gamma-aminobutyric acid (GABA) and glutamate contribute to diabetic gastrointestinal abnormalities. Hence, we examined the impact of prolonged treatment with insulin and magnesium supplement on the expression pattern of GABA type A (GABA-A), GABA-B and N-methyl-D-aspartate (NMDA) glutamate receptors as well as nitric oxide synthase 1 (NOS-1) in the stomach of type 2 diabetic rats. Twenty-four male Wistar rats were randomized to 4 groups (6 rats each): 1) control, 2) type 2 diabetes: rats fed with a high fat diet for 3 months + low dose of streptozotocin (35 mg/kg), 3) type 2 diabetes + magnesium, and 4) type 2 diabetes + insulin. The expression of NOS-1 as well as GABA-A, GABA-B, and NMDA receptors was detected using western blotting. NOS-1 expression was substantially diminished (p<0.01) while the expression of GABA-A (p<0.001), GABA-B (p<0.001), and NMDA (p<0.001) receptors was enhanced in the stomach of diabetic rats relative to control. Treatment with magnesium and insulin improved NOS-1 expression in diabetic rats, although this effect was greater in magnesium treatment alone. Magnesium also restored the expression of GABA-A and GABA-B receptors in diabetic rats to control values. Moreover, insulin treatment improved GABA-A receptor expression in diabetic rats (p<0.05). No considerable alterations were detected in NMDA receptor level in the treatment groups. The results suggest a significant role of magnesium and insulin in improving gastric motility and secretory disorders associated with diabetes through modifying the expression of GABAergic receptors.

The role of fatty acid-binding protein 5 and 7 on locomotor, anxiety and social behavior: Interaction with NMDA signaling

The endocannabinoid system has been shown to be a powerful mediator of anxiety, learning and memory, as well as nociception behaviors. Exogenous cannabinoids like delta-9-tetrahydrocannabinol mimic the naturally occurring endogenous cannabinoids found in the mammalian central and peripheral nervous system. The hydrophobic properties of endocannabinoids mean that these psychoactive compounds require help with cellular transport. A family of lipid intracellular carriers called fatty acid-binding proteins (FABPs) can bind to endocannabinoids. Pharmacological inhibition or genetic deletion of FABP subtypes 5 and 7 elevates whole-brain anandamide (AEA) levels, a type of endocannabinoid. This study examined locomotor behavior, anxiety-like behavior, and social behavior in FABP5-/- and FABP7-/- mice. Furthermore, we measured N-methyl-D-aspartate (NMDA) receptor levels in the brain to help identify potential underlying mechanisms related to the behavioral findings. Results showed that both male and female FABP5-/- mice exhibited significantly lower activity when compared with both FABP5/7+/+ (control) and FABP7-/-. For social behavior, male, but not female, FABP5-/- mice spent more time interacting with novel mice compared with controls (FABP5/7+/+) and FABP7-/- mice. No significant difference was found for anxiety-like behavior. Results from the NMDA autoradiography revealed [3H] MK-801 binding to be significantly increased within sub-regions of the striatum in FABP7-/- compared with control. In summary, these results show that FABP5 deficiency plays a significant role in locomotion activity, exploratory behavior, as well as social interaction. Furthermore, FABP7 deficiency is shown to play an important role in NMDA receptor expression, while FABP5 does not.

Scorpion venom heat-resistant synthesized peptide ameliorates epileptic seizures and imparts neuroprotection in rats mediated by NMDA receptors

Finding new and effective natural products for designing antiepileptic drugs is highly important in the scientific community. The scorpion venom heat-resistant peptide (SVHRP) was purified from Buthus martensii Karsch scorpion venom, and subsequent analysis of the amino acid sequence facilitated the synthesis of a peptide known as scorpion venom heat-resistant synthesis peptide (SVHRSP) using a technique for peptide synthesis. Previous studies have demonstrated that the SVHRSP can inhibit neuroinflammation and provide neuroprotection. This study aimed to investigate the antiepileptic effect of SVHRSP on both acute and chronic kindling seizure models by inducing seizures in male rats through intraperitoneal administration of pentylenetetrazole (PTZ). Additionally, an N-methyl-D-aspartate (NMDA)-induced neuronal injury model was used to observe the anti-excitotoxic effect of SVHRSP in vitro. Our findings showed that treatment with SVHRSP effectively alleviated seizure severity, prolonged latency, and attenuated neuronal loss and glial cell activation. It also demonstrated the prevention of alterations in the expression levels of NMDA receptor subunits and phosphorylated p38 MAPK protein, as well as an improvement in spatial reference memory impairment during Morris water maze (MWM) testing in PTZ-kindled rats. In vitro experiments further revealed that SVHRSP was capable of attenuating neuronal action potential firing, inhibiting NMDA receptor currents and intracellular calcium overload, and reducing neuronal injury. These results suggest that the antiepileptic and neuroprotective effects of SVHRSP may be mediated through the regulation of NMDA receptor function and expression. This study provides new insight into therapeutic strategies for epilepsy.

3'-Daidzein Sulfonate Sodium Protects against Glutamate-induced Neuronal Injuries by Regulating NMDA Receptors.

It was previously found that 3'-Daidzein Sulfonate Sodium (DSS) exhibits protective effects on cerebral ischemia/reperfusion injury (CI/RI). This study aimed to explore the underlying molecular mechanisms involved in the neuroprotective effects of DSS against ischemic stroke. In this study, rats with transient middle cerebral artery occlusion (tMCAO) were used as an in vivo model, whereas PC12 cells treated with glutamate alone and rat primary cortical neurons treated with the combination of glutamate and glycine were used as in vitro models. Cell viability and lactate dehydrogenase (LDH) release were used to evaluate cell injury. Cell apoptosis was determined by flow cytometry. Quantitative polymerase chain reaction (qPCR), Western blotting, and immunofluorescent staining methods were used to determine the mRNA expressions and protein levels and location. It was found that DSS significantly suppressed the impaired viability of PC12 cells induced by glutamate. DSS also increased cell viability while reducing the LDH release and apoptosis in primary cortical neurons injured by glutamate and glycine. In addition, DSS decreased GluN2B subunit expression while enhancing the expressions of GluN2A subunit and PSD95 in tMCAO rats' brains. This study demonstrated that DSS protects against excitotoxic damage in neurons induced by CI/RI through regulating the expression of NMDA receptors and PSD95. Our findings provide experimental evidence for the potential clinical administration of DSS in ischemic stroke.

Monosodium glutamate altered renal architecture and modulated expression of NMDA-R, eNOS, and nNOS in normotensive and hypertensive rats

Monosodium glutamate (MSG) administration has been shown to pronounce hypertension and oxidative status with increased renal blood flow (RBF), however, the precise mechanisms of action have never been demonstrated. This study aimed to investigate the MSG action by studying the alteration in renal architecture and specific protein expression in 2-kidney-1-clip hypertensive comparing to sham operative normotensive rats. The administered doses of MSG were 80, 160, or 320 mg/kg BW daily for 8 weeks. Using routine chemical staining, the congestion of glomerular capillaries, a lesser renal corpuscles and glomeruli size, a widen Bowman capsule's space, an increase in mesangial cell proliferation and mesangial matrix, renal interstitial fibrosis, focal cloudy swelling of renal tubular epithelial cells were observed. Immunological study revealed an increase in the expression of N-methyl-D-aspartate receptor (NMDA-R) and endothelial nitric oxide synthase (eNOS) but a decrease in neuronal NOS (nNOS). It is suggested that MSG may upregulate the NMDA-R levels which responsible for the oxidative stress, glomerular injury, and renal interstitial fibrosis. The NMDA-R may also stimulate eNOS overexpression which resulted in renal microvascular dilatation, a raise in RBF and GFR, and natriuresis and diuresis promotion. Long-term exposure of MSG may trigger adaptation of tubuloglomerular feedback through nNOS downregulation.

Chronic Vagotomy Blunts Cardiorespiratory Reflex Responses Through Pre- and Postsynaptic Effects in the Brainstem Nucleus Tractus Solitarii (nTS)

Sensory information from the heart, lungs, and gastrointestinal tract travels to the brain via afferents of the paired vagus nerves, where it is first integrated in the brainstem nTS that critically contributes to cardiorespiratory function. We have shown that reducing input to the nTS by unilaterally transecting the vagus nerve (vagotomy) induces astrocyte reactivity and microglial activation, and reduces sighs in hypoxia. However, the cardiorespiratory effects of vagotomy and contributing mechanisms are not well understood. We hypothesized that chronic vagotomy blunts cardiorespiratory reflex responses to vagal afferent stimulation via reduced nTS neuronal activity. Male Sprague-Dawley rats (6-wk) underwent right cervical vagotomy (or sham surgery) caudal to the nodose ganglion. After 7 days rats were anesthetized, ventilated, and instrumented to record mean arterial pressure (MAP), heart rate (HR), splanchnic sympathetic and phrenic nerve activity (SSNA and PhrNA, respectively), which decreased in response to vagal afferent stimulation in sham animals. Vagotomy blunted these decreases in MAP, SSNA, and PhrNA compared to shams. In rats expressing the calcium indicator GCaMP8m in nTS neurons, vagotomy also reduced neuronal Ca2+ responses to afferent stimulation both in vivo (photometry) and in vitro (live slice imaging). We then hypothesized that these changes were due to altered signaling at the level of the tripartite synapse, where astrocytes enwrap the sensory afferent-nTS soma synapse. We found that there is likely a vagal afferent contribution to the altered reflex responses, as vagotomy reduced presynaptic Ca2+ responses in vagal afferent terminals to solitary tract stimulation in the brainstem slice. Glutamate agonists, which induce similar cardiorespiratory responses as vagal stimulation, were nanoinjected into the nTS to determine if there was a postsynaptic contribution to the blunted responses as well. Responses to glutamate injection were also blunted following vagotomy, indicating that astrocytic glutamate uptake or nTS soma glutamate receptor function may be altered. Blocking astrocytic excitatory amino acid transporters, which remove extracellular glutamate in the nTS induced similar baseline effects and did not restore cardiorespiratory responses to glutamate in vagotomy. However, nanoinjection of NMDA into the nTS to activate ionotropic glutamate receptors mimicked the blunted responses to glutamate following vagotomy, with no difference in responses to AMPA nanoinjection. Likewise, immunohistochemistry and Western blot showed that vagotomy reduced NMDA receptor subunit expression in the nTS. Together these results indicate that chronic vagotomy blunts cardiorespiratory responses to vagal afferent stimulation, likely through reduced presynaptic activation and decreased NMDA receptor expression and function. These studies will help improve our understanding of how afferent input induces neuroplasticity within the nTS, and the resulting impacts on cardiorespiratory function in health and disease. NIH HL132836, HL128454, HL98602, T32OD011126. 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.

Limb-Clasping Response in NMDA Receptor Palmitoylation-Deficient Mice.

Proper regulation of N-methyl-D-aspartate-type glutamate receptor (NMDA receptor) expression is responsible for excitatory synaptic functions in the mammalian brain. NMDA receptor dysfunction can cause various neuropsychiatric disorders and neurodegenerative diseases. Posttranslational protein S-palmitoylation, the covalent attachment of palmitic acid to intracellular cysteine residues via thioester bonds, occurs in the carboxyl terminus of GluN2B, which is the major regulatory NMDA receptor subunit. Mutations of three palmitoylatable cysteine residues in the membrane-proximal cluster of GluN2B to non-palmitoylatable serine (3CS) lead to the dephosphorylation of GluN2B Tyr1472 in the hippocampus and cerebral cortex, inducing a reduction in the surface expression of GluN2B-containig NMDA receptors. Furthermore, adult GluN2B 3CS homozygous mice demonstrated a definite clasping response without abnormalities in the gross brain structure, other neurological reflexes, or expression levels of synaptic proteins in the cerebrum. This behavioral disorder, observed in the GluN2B 3CS knock-in mice, indicated that complex higher brain functions are coordinated through the palmitoylation-dependent regulation of NMDA receptors in excitatory synapses.

Quercetin alleviates chronic unpredictable mild stress-induced depression-like behavior by inhibiting NMDAR1 with α2δ-1 in rats.

Depression is a serious mental disorder and the most prevalent cause of disability and suicide worldwide. Chronic unpredictable mild stress (CUMS) can lead to a significant acceleration of depression development. Quercetin (Que) is a flavonoid compound with a wide range of pharmacological effects. Recent studies have shown that quercetin can improve CUMS-induced depression-like behavior, but the mechanism of its improvement is still unclear. α2δ-1 is a regulatory subunit of voltage-gated calcium channel, which can interact with N-methyl-D-aspartate receptor (NMDAR) to form a complex. In this study, we found that Que could inhibit the increase of α2δ-1 and NMDAR expression in rat hypothalamus induced by CUMS. In pain, chronic hypertension and other studies have shown that α2δ-1 interacts with the NMDAR to form a complex, which subsequently affects the expression level of NMDAR. Consequently, the present study aimed to investigate the antidepressant effect of Que invivo and invitro and to explore its mechanism of action in terms of the interaction between α2δ-1 and NMDAR. Rats were randomly exposed to two stressors every day for 4 weeks to establish a CUMS rat model, then sucrose preference test (SPT), forced swimming test (FST), tail suspension test (TST), and open field test (OFT) were performed to detect the behavior of CUMS rats, so as to evaluate whether the CUMS rat model was successfully established and the improvement effect of Que on CUMS-induced depression-like behavior in rats. Experimental techniques such as serum enzyme-linked immunosorbent assay (ELISA), immunofluorescence, Western blot, and co-immunoprecipitation, as well as invitro experiments, were used to investigate the mechanisms by which Que exerts its antidepressant effects. Behavioral and ELISA test results showed that Que could produce a reduction in the excitability of the hypothalamic-pituitary-adrenal (HPA) axis in CUMS rats and lead to significant improvements in their depressive behavior. Western blot, immunofluorescence, and co-immunoprecipitation experiments showed that Que produced a decrease in NMDAR1 and α2δ-1 expression levels and interfered with α2δ-1 and NMDAR1 binding. In addition, the neural regulation mechanism of Que on antidepressant effect in PC12 cells knocked out α2δ-1 gene was further verified. Cellular experiments demonstrated that Que led to a reversal of up-regulation of NMDAR1 and α2δ-1 expression levels in corticosterone-injured PC12 cells, while Que had no effects on NMDAR1 expression in PC12 cells with the α2δ-1 gene knockout. Que has a good antidepressant effect and can significantly improve the depression-like behavior caused by CUMS. It exerts antidepressant effects by inhibiting the expression level of α2δ-1, interfering with the interaction between α2δ-1 and NMDAR, and then reducing the excitability of the HPA axis.

Sustained morphine exposure alters spinal NMDA receptor and astrocyte expression and exacerbates chronic pain behavior in female rats.

Sustained opioid use has long-term negative impacts on future pain experience, particularly in women. This study aimed to investigate the underlying spinal neurobiology of this clinical observation in an experimental model of joint pain. In this study, we tested the hypothesis that sustained opioid treatment exacerbates chronic pain responses and alters spinal cord dorsal horn astrogliosis and the expression of GluN2B-containing N-methyl-d-aspartate receptors in female rats. Subcutaneous morphine (3 mg/kg) or saline was administered twice daily for 1 week before inducing a model of joint knee pain (intra-articular injection of 2 mg of monosodium iodoacetate [MIA]) in adult female Sprague-Dawley rats, with pain-free controls receiving 50 µL of saline. Pain behavior (weight-bearing and mechanical paw withdrawal thresholds) was measured at baseline and at intervals thereafter. Twice-daily morphine/saline treatment was continued for up to 3 weeks after intra-articular injections, and spinal cord tissue was collected for Western blot analyses. Area under the curve analysis of weight-bearing asymmetry confirmed a significant exacerbation of pain behavior in the morphine/MIA group, compared with the saline/MIA group (F(3,18) = 46.3, P < 0.0001), despite comparable joint damage in both groups. Sustained morphine treatment was associated with significant elevations in dorsal horn expression of astrocytic glial fibrillary acidic protein (27 ± 5% increase) and neuronal GluN2B (80 ± 30% increase), but not microglial IBA1, irrespective of the model of joint pain. These data suggest that sustained morphine treatment in female rats drives spinal cord plasticity, including spinal astrogliosis and the expression of GluN2B-containing N-methyl-d-aspartate receptors, priming the dorsal horn to incoming sensory inputs and producing exacerbated pain responses.

Perioperative Ketamine and Cancer Recurrence: A Comprehensive Review.

Cancer is a significant global health threat and a leading cause of death worldwide. Effective early-stage interventions, particularly surgery, can potentially cure many solid tumors. However, the risk of postoperative cancer recurrence remains high. Recent research highlights the influence of perioperative anesthetic and analgesic choices on the fate of residual cancer cells, potentially affecting recurrence risks. Among these agents, ketamine-a well-known anesthetic and analgesic-has garnered interest due to its antitumor properties, mainly through inhibiting the N-methyl-D-aspartate (NMDA) receptor found in various cancer tissues. Additionally, ketamine's potential immunomodulatory effects, given the expression of NMDA receptors on immune cells, suggest that it plays a significant role during the perioperative period. This review synthesizes current evidence on ketamine's impact on cancer cell biology, inflammation, immune modulation, and the role of the gut microbiota, proposing ketamine as a promising agent for enhancing oncological outcomes.

Early developmental changes in a rat model of malformations of cortical development: Abnormal neuronal migration and altered response to NMDA-induced excitotoxic injury

Malformations of cortical development (MCDs) are caused by abnormal neuronal migration processes during the fetal period and are a major cause of intractable epilepsy in infancy. However, the timing of hyperexcitability or epileptogenesis in MCDs remains unclear. To identify the early developmental changes in the brain of the MCD rat model, which exhibits increased seizure susceptibility during infancy (P12–15), we analyzed the pathological changes in the brains of MCD model rats during the neonatal period and tested NMDA-induced seizure susceptibility.Pregnant rats were injected with two doses of methylazoxymethanol acetate (MAM, 15 mg/kg, i.p.) to induce MCD, while controls were administered normal saline. The cortical development of the offspring was measured by performing magnetic resonance imaging (MRI) on postnatal days (P) 1, 5, and 8. At P8, some rats were sacrificed for immunofluorescence, Golgi staining, and Western analysis. In another set of rats, the number and latency to onset of spasms were monitored for 90 min after the NMDA (5 mg/kg i.p.) injection at P8.In MCD rats, in vivo MR imaging showed smaller brain volume and thinner cortex from day 1 after birth (p < 0.001). Golgi staining and immunofluorescence revealed abnormal neuronal migration, with a reduced number of neuronal cell populations and less dendritic arborization at P8. Furthermore, MCD rats exhibited a significant reduction in the expression of NMDA receptors and AMPAR4, along with an increase in AMPAR3 expression (p < 0.05). Although there was no difference in the latency to seizure onset between MCD rats and controls, the MCD rats survived significantly longer than the controls.These results provide insights into the early developmental changes in the cortex of a MCD rat model and suggest that delayed and abnormal neuronal development in the immature brain is associated with a blunted response to NMDA-induced excitotoxic injury. These developmental changes may be involved in the sudden onset of epilepsy in patients with MCD or prenatal brain injury.

The Expression and Functionality of CB1R-NMDAR Complexes Are Decreased in A Parkinson's Disease Model.

One of the hallmarks of Parkinson's disease (PD) is the alteration in the expression and function of NMDA receptor (NMDAR) and cannabinoid receptor 1 (CB1R). The presence of CB1R-NMDAR complexes has been described in neuronal primary cultures. The activation of CB1R in CB1R-NMDAR complexes was suggested to counteract the detrimental NMDAR overactivation in an AD mice model. Thus, we aimed to explore the role of this receptor complex in PD. By using Bioluminescence Resonance Energy Transfer (BRET) assay, it was demonstrated that α-synuclein induces a reorganization of the CB1R-NMDAR complex in transfected HEK-293T cells. Moreover, α-synuclein treatment induced a decrease in the cAMP and MAP kinase (MAPK) signaling of both CB1R and NMDAR not only in transfected cells but also in neuronal primary cultures. Finally, the interaction between CB1R and NMDAR was studied by Proximity Ligation Assay (PLA) in neuronal primary cultures, where it was observed that the expression of CB1R-NMDAR complexes was decreased upon α-synuclein treatment. These results point to a role of CB1R-NMDAR complexes as a new therapeutic target in Parkinson's disease.