Extracting and Analyzing the S-Parameters of Vertical Interconnection Structures in 3D Glass Packaging.

In order to effectively employ through-glass vias (TGVs) for high-frequency software package design, it is crucial to accurately characterize the S-parameters of vertical interconnection structures in 3D glass packaging. A methodology is proposed for the extraction of precise S-parameters using the transmission matrix (T-matrix) to analyze and evaluate the insertion loss (IL) and reliability of TGV interconnections. The method presented herein enables the handling of a diverse range of vertical interconnections, encompassing micro-bumps, bond-wires, and a variety of pads. Additionally, a test structure for coplanar waveguide (CPW) TGVs is constructed, accompanied by a comprehensive description of the equations and measurement procedure employed. The outcomes of the investigation demonstrate a favorable concurrence between the simulated and measured results, with analyses and measurements conducted up to 40 GHz.

GluN2D subunit-containing NMDA receptors regulate reticular thalamic neuron function and seizure susceptibility.

Thalamic regulation of cortical function is important for several behavioral aspects including attention and sensorimotor control. This region has also been studied for its involvement in seizure activity. Among the NMDA receptor subunits GluN2C and GluN2D are particularly enriched in several thalamic nuclei including nucleus reticularis of the thalamus (nRT). We have previously found that GluN2C deletion does not have a strong influence on the basal excitability and burst firing characteristics of reticular thalamus neurons. Here we find that GluN2D ablation leads to reduced depolarization-induced spike frequency and reduced hyperpolarization-induced rebound burst firing in nRT neurons. Furthermore, reduced inhibitory neurotransmission was observed in the ventrobasal thalamus (VB). A model with preferential downregulation of GluN2D from parvalbumin (PV)-positive neurons was generated. Conditional deletion of GluN2D from PV neurons led to a decrease in excitability and burst firing. In addition, reduced excitability and burst firing was observed in the VB neurons together with reduced inhibitory neurotransmission. Finally, young mice with GluN2D downregulation in PV neurons showed significant resistance to pentylenetetrazol-induced seizure and differences in sensitivity to isoflurane anesthesia but were normal in other behaviors. Conditional deletion of GluN2D from PV neurons also affected expression of other GluN2 subunits and GABA receptor in the nRT. Together, these results identify a unique role of GluN2D-containing receptors in the regulation of thalamic circuitry and seizure susceptibility which is relevant to mutations in GRIN2D gene found to be associated with pediatric epilepsy.

Cocaine preference and neuroadaptations are maintained by astrocytic NMDA receptors in the nucleus accumbens.

Cocaine-associated memories induce cravings and interfere with the ability of users to cease cocaine use. Reducing the strength of cue-drug memories by facilitating extinction may have therapeutic value for the treatment of cocaine addiction. Here, we demonstrate the expression of GluN1/2A/2C NMDA receptor currents in astrocytes in the nucleus accumbens core. Selective ablation of GluN1 subunit from astrocytes in the nucleus accumbens enhanced extinction of cocaine preference memory but did not affect cocaine conditioning or reinstatement. Repeated cocaine exposure up-regulated GluN2C subunit expression and increased astrocytic NMDA receptor currents. Furthermore, intra-accumbal inhibition of GluN2C/2D-containing receptors and GluN2C subunit deletion facilitated extinction of cocaine memory. Cocaine-induced neuroadaptations including dendritic spine maturation and AMPA receptor recruitment were absent in GluN2C knockout mice. Impaired retention of cocaine preference memory in GluN2C knockout mice was restored by exogenous administration of recombinant glypican 4. Together, these results identify a previously unknown astrocytic GluN2C-containing NMDA receptor mechanism underlying maintenance of cocaine preference memory.

Dysfunction of Glutamate Delta-1 Receptor-Cerebellin 1 Trans-Synaptic Signaling in the Central Amygdala in Chronic Pain.

Chronic pain is a debilitating condition involving neuronal dysfunction, but the synaptic mechanisms underlying the persistence of pain are still poorly understood. We found that the synaptic organizer glutamate delta 1 receptor (GluD1) is expressed postsynaptically at parabrachio-central laterocapsular amygdala (PB-CeLC) glutamatergic synapses at axo-somatic and punctate locations on protein kinase C δ -positive (PKCδ+) neurons. Deletion of GluD1 impairs excitatory neurotransmission at the PB-CeLC synapses. In inflammatory and neuropathic pain models, GluD1 and its partner cerebellin 1 (Cbln1) are downregulated while AMPA receptor is upregulated. A single infusion of recombinant Cbln1 into the central amygdala led to sustained mitigation of behavioral pain parameters and normalized hyperexcitability of central amygdala neurons. Cbln2 was ineffective under these conditions and the effect of Cbln1 was antagonized by GluD1 ligand D-serine. The behavioral effect of Cbln1 was GluD1-dependent and showed lateralization to the right central amygdala. Selective ablation of GluD1 from the central amygdala or injection of Cbln1 into the central amygdala in normal animals led to changes in averse and fear-learning behaviors. Thus, GluD1-Cbln1 signaling in the central amygdala is a teaching signal for aversive behavior but its sustained dysregulation underlies persistence of pain. Significance statement: Chronic pain is a debilitating condition which involves synaptic dysfunction, but the underlying mechanisms are not fully understood. Our studies identify a novel mechanism involving structural synaptic changes in the amygdala caused by impaired GluD1-Cbln1 signaling in inflammatory and neuropathic pain behaviors. We also identify a novel means to mitigate pain in these conditions using protein therapeutics.

Astrocytic NMDA Receptors in the Basolateral Amygdala Contribute to Facilitation of Fear Extinction.

BACKGROUND: Enhancement of N-methyl-D-aspartate (NMDA) receptor function using glycine-site agonist D-cycloserine is known to facilitate fear extinction, providing a means to augment cognitive behavioral therapy in anxiety disorders. A novel class of glycine-site agonists has recently been identified, and we have found that the prototype, AICP, is more effective than D-cycloserine in modulating neuronal function. METHODS: Using novel glycine-site agonist AICP, local infusion studies, and genetic models, we elucidated the role of GluN2C-containing receptors in fear extinction. RESULTS: We tested the effect of intracerebroventricular injection of AICP on fear extinction and found a robust facilitation of fear extinction. This effect was dependent on GluN2C subunit, consistent with superagonist action of AICP at GluN2C-containing receptors. Local infusion studies in wild-type and GluN2C knockout mice suggested that AICP produces its effect via GluN2C-containing receptors in the basolateral amygdala (BLA). Furthermore, consistent with astrocytic expression of GluN2C subunit in the amygdala, we found that AICP did not facilitate fear extinction in mice with conditional deletion of obligatory GluN1 subunit from astrocytes. Importantly, chemogenetic activation of astrocytes in the basolateral amygdala facilitated fear extinction. Acutely, AICP was found to facilitate excitatory neurotransmission in the BLA via presynaptic GluN2C-dependent mechanism. Immunohistochemical studies suggest that AICP-mediated facilitation of fear extinction involves synaptic insertion of α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor GluA1 subunit. CONCLUSION: These results identify a unique role of astrocytic NMDA receptors composed of GluN2C subunit in extinction of conditioned fear memory and demonstrate that further development of recently identified superagonists of GluN2C-containing receptors may have utility for anxiety disorders.

Glutamate Delta-1 Receptor Regulates Inhibitory Neurotransmission in the Nucleus Accumbens Core and Anxiety-Like Behaviors.

Glutamate delta-1 receptor (GluD1) is a member of the ionotropic glutamate receptor family expressed at excitatory synapses and functions as a synaptogenic protein by interacting with presynaptic neurexin. We have previously shown that GluD1 plays a role in the maintenance of excitatory synapses in a region-specific manner. Loss of GluD1 leads to reduced excitatory neurotransmission in medium spiny neurons (MSNs) in the dorsal striatum, but not in the ventral striatum (both core and shell of the nucleus accumbens (NAc)). Here, we found that GluD1 loss leads to reduced inhibitory neurotransmission in MSNs of the NAc core as evidenced by a reduction in the miniature inhibitory postsynaptic current frequency and amplitude. Presynaptic effect of GluD1 loss was further supported by an increase in paired pulse ratio of evoked inhibitory responses indicating reduced release probability. Furthermore, analysis of GAD67 puncta indicated a reduction in the number of putative inhibitory terminals. The changes in mIPSC were independent of cannabinoid or dopamine signaling. A role of feed-forward inhibition was tested by selective ablation of GluD1 from PV neurons which produced modest reduction in mIPSCs. Behaviorally, local ablation of GluD1 from NAc led to hypolocomotion and affected anxiety- and depression-like behaviors. When GluD1 was ablated from the dorsal striatum, several behavioral phenotypes were altered in opposite manner compared to GluD1 ablation from NAc. Our findings demonstrate that GluD1 regulates inhibitory neurotransmission in the NAc by a combination of pre- and postsynaptic mechanisms which is critical for motor control and behaviors relevant to neuropsychiatric disorders.

Energetic-Materials-Driven Synthesis of Graphene-Encapsulated Tin Oxide Nanoparticles for Sodium-Ion Batteries.

By evenly mixing polytetrafluoroethylene-silicon energetic materials (PTFE-Si EMs) with tin oxide (SnO2) particles, we demonstrate a direct synthesis of graphene-encapsulated SnO2 (Gr-SnO2) nanoparticles through the self-propagated exothermic reaction of the EMs. The highly exothermic reaction of the PTFE-Si EMs released a huge amount of heat that induced an instantaneous temperature rise at the reaction zone, and the rapid expansion of the gaseous SiF4 product provided a high-speed gas flow for dispersing the molten particles into finer nanoscale particles. Furthermore, the reaction of the PTFE-NPs with Si resulted in a simultaneous synthesis of graphene that encapsulated the SnO2 nanoparticles in order to form the core-shell nanostructure. As sodium storage material, the graphene-encapsulated SnO2 nanoparticles exhibit a good cycling performance, superior rate capability, and a high initial Coulombic efficiency of 85.3%. This proves the effectiveness of our approach for the scalable synthesis of core-shell-structured graphene-encapsulated nanomaterials.

Facilitation of GluN2C-containing NMDA receptors in the external globus pallidus increases firing of fast spiking neurons and improves motor function in a hemiparkinsonian mouse model.

Globus pallidus externa (GPe) is a nucleus in the basal ganglia circuitry involved in the control of movement. Recent studies have demonstrated a critical role of GPe cell types in Parkinsonism. Specifically increasing the function of parvalbumin (PV) neurons in the GPe has been found to facilitate motor function in a mouse model of Parkinson's disease (PD). The knowledge of contribution of NMDA receptors to GPe function is limited. Here, we demonstrate that fast spiking neurons in the GPe express NMDA receptor currents sensitive to GluN2C/GluN2D-selective inhibitors and glycine site agonist with higher efficacy at GluN2C-containing receptors. Furthermore, using a novel reporter model, we demonstrate the expression of GluN2C subunits in PV neurons in the GPe which project to subthalamic nuclei. GluN2D subunit was also found to localize to PV neurons in GPe. Ablation of GluN2C subunit does not affect spontaneous firing of fast spiking neurons. In contrast, facilitating the function of GluN2C-containing receptors using glycine-site NMDA receptor agonists, D-cycloserine (DCS) or AICP, increased the spontaneous firing frequency of PV neurons in a GluN2C-dependent manner. Finally, we demonstrate that local infusion of DCS or AICP into the GPe improved motor function in a mouse model of PD. Together, these results demonstrate that GluN2C-containing receptors and potentially GluN2D-containing receptors in the GPe may serve as a therapeutic target for alleviating motor dysfunction in PD and related disorders.

Striatal glutamate delta-1 receptor regulates behavioral flexibility and thalamostriatal connectivity.

Impaired behavioral flexibility and repetitive behavior is a common phenotype in autism and other neuropsychiatric disorders, but the underlying synaptic mechanisms are poorly understood. The trans-synaptic glutamate delta (GluD)-Cerebellin 1-Neurexin complex, critical for synapse formation/maintenance, represents a vulnerable axis for neuropsychiatric diseases. We have previously found that GluD1 deletion results in reversal learning deficit and repetitive behavior. In this study, we show that selective ablation of GluD1 from the dorsal striatum impairs behavioral flexibility in a water T-maze task. We further found that striatal GluD1 is preferentially found in dendritic shafts, and more frequently associated with thalamic than cortical glutamatergic terminals suggesting localization to projections from the thalamic parafascicular nucleus (Pf). Conditional deletion of GluD1 from the striatum led to a selective loss of thalamic, but not cortical, terminals, and reduced glutamatergic neurotransmission. Optogenetic studies demonstrated functional changes at thalamostriatal synapses from the Pf, but no effect on the corticostriatal system, upon ablation of GluD1 in the dorsal striatum. These studies suggest a novel molecular mechanism by which genetic variations associated with neuropsychiatric disorders may impair behavioral flexibility, and reveal a unique principle by which GluD1 subunit regulates forebrain circuits.

HIV-1 Tat-Induced Astrocytic Extracellular Vesicle miR-7 Impairs Synaptic Architecture.

Although combination antiretroviral therapy (cART) has improved the health of millions of those living with HIV-1 (Human Immunodeficiency Virus, Type 1), the penetration into the central nervous system (CNS) of many such therapies is limited, thereby resulting in residual neurocognitive impairment commonly referred to as NeuroHIV. Additionally, while cART has successfully suppressed peripheral viremia, cytotoxicity associated with the presence of viral Transactivator of transcription (Tat) protein in tissues such as the brain, remains a significant concern. Our previous study has demonstrated that both HIV-1 Tat as well as opiates such as morphine, can directly induce synaptic alterations via independent pathways. Herein, we demonstrate that exposure of astrocytes to HIV-1 protein Tat mediates the induction and release of extracellular vesicle (EV) microRNA-7 (miR-7) that is taken up by neurons, leading in turn, to downregulation of neuronal neuroligin 2 (NLGN2) and ultimately to synaptic alterations. More importantly, we report that these impairments could be reversed by pretreatment of neurons with a neurotrophic factor platelet-derived growth factor-CC (PDGF-CC). Graphical Abstract.

Modulation of burst firing of neurons in nucleus reticularis of the thalamus by GluN2C-containing NMDA receptors.

The GluN2C subunit of the NMDA receptor is enriched in the neurons in nucleus reticularis of the thalamus (nRT), but its role in regulating their function is not well understood. We found that deletion of GluN2C subunit did not affect spike frequency in response to depolarizing current injection or hyperpolarization-induced rebound burst firing of nRT neurons. D-cycloserine or CIQ (GluN2C/GluN2D positive allosteric modulator) did not affect the depolarization-induced spike frequency in nRT neurons. A newly identified highly potent and efficacious co-agonist of GluN1/GluN2C NMDA receptors, AICP, was found to reduce the spike frequency and burst firing of nRT neurons in wildtype but not GluN2C knockout. This effect was potentially due to facilitation of GluN2C-containing receptors because inhibition of NMDA receptors by AP5 did not affect spike frequency in nRT neurons. We evaluated the effect of intracerebroventricular injection of AICP. AICP did not affect basal locomotion or prepulse inhibition but facilitated MK-801-induced hyperlocomotion. This effect was observed in wildtype but not in GluN2C knockout mice demonstrating that AICP produces GluN2C-selective effects in vivo Using a chemogenetic approach we examined the role of nRT in this behavioral effect. Gq or Gi coupled DREADDs were selectively expressed in nRT neurons using cre-dependent viral vectors and PV-Cre mouse line. We found that similar to AICP effect, activation of Gq but not Gi coupled DREADD facilitated MK-801-induced hyperlocomotion. Together, these results identify a unique role of GluN2C-containing receptors in the regulation of nRT neurons and suggest GluN2C-selective in vivo targeting of NMDA receptors by AICP. SIGNIFICANCE STATEMENT: The nucleus reticularis of the thalamus composed of GABAergic neurons is termed as guardian of the gateway and is an important regulator of corticothalamic communication which may be impaired in autism, non-convulsive seizures and other conditions. We found that strong facilitation of tonic activity of GluN2C subtype of NMDA receptors using AICP, a newly identified glycine-site agonist of NMDA receptors, modulates the function of reticular thalamus neurons. AICP was also able to produce GluN2C-dependent behavioral effects in vivo. Together, these finding identify a novel mechanism and a pharmacological tool to modulate activity of reticular thalamic neurons in disease states.

Redox-sensitive calcium/calmodulin-dependent protein kinase IIα in angiotensin II intra-neuronal signaling and hypertension.

Dysregulation of brain angiotensin II (AngII) signaling results in modulation of neuronal ion channel activity, an increase in neuronal firing, enhanced sympathoexcitation, and subsequently elevated blood pressure. Studies over the past two decades have shown that these AngII responses are mediated, in part, by reactive oxygen species (ROS). However, the redox-sensitive target(s) that are directly acted upon by these ROS to execute the AngII pathophysiological responses in neurons remain unclear. Calcium/calmodulin-dependent protein kinase II (CaMKII) is an AngII-activated intra-neuronal signaling protein, which has been suggested to be redox sensitive as overexpressing the antioxidant enzyme superoxide dismutase attenuates AngII-induced activation of CaMKII. Herein, we hypothesized that the neuronal isoform of CaMKII, CaMKII-alpha (CaMKIIα), is a redox-sensitive target of AngII, and that mutation of potentially redox-sensitive amino acids in CaMKIIα influences AngII-mediated intra-neuronal signaling and hypertension. Adenoviral vectors expressing wild-type mouse CaMKIIα (Ad.wtCaMKIIα) or mutant CaMKIIα (Ad.mutCaMKIIα) with C280A and M281V mutations were generated to overexpress either CaMKIIα isoform in mouse catecholaminergic cultured neurons (CATH.a) or in the brain subfornical organ (SFO) of hypertensive mice. Overexpressing wtCaMKIIα exacerbated AngII pathophysiological responses as observed by a potentiation of AngII-induced inhibition of voltage-gated K+ current, enhanced in vivo pressor response following intracerebroventricular injection of AngII, and sensitization to chronic peripheral infusion of AngII resulting in a more rapid increase in blood pressure. In contrast, expressing the mutant CaMKIIα in CATH.a neurons or the SFO failed to intensify these AngII responses. Taken together, these data identify neuronal CaMKIIα as a redox-sensitive signaling protein that contributes to AngII-induced neuronal activation and hypertension.

Differential effect of NMDA receptor GluN2C and GluN2D subunit ablation on behavior and channel blocker-induced schizophrenia phenotypes.

The GluN2C- and GluN2D-containing NMDA receptors are distinct from GluN2A- and GluN2B-containing receptors in many aspects including lower sensitivity to Mg2+ block and lack of desensitization. Recent studies have highlighted the unique contribution of GluN2C and GluN2D subunits in various aspects of neuronal and circuit function and behavior, however a direct comparison of the effect of ablation of these subunits in mice on pure background strain has not been conducted. Using knockout-first strains for the GRIN2C and GRIN2D produced on pure C57BL/6N strain, we compared the effect of partial or complete ablation of GluN2C and GluN2D subunit on various behaviors relevant to mental disorders. A large number of behaviors described previously in GluN2C and GluN2D knockout mice were reproduced in these mice, however, some specific differences were also observed possibly representing strain effects. We also examined the response to NMDA receptor channel blockers in these mouse strains and surprisingly found that unlike previous reports GluN2D knockout mice were not resistant to phencyclidine-induced hyperlocomotion. Interestingly, the GluN2C knockout mice showed reduced sensitivity to phencyclidine-induced hyperlocomotion. We also found that NMDA receptor channel blocker produced a deficit in prepulse inhibition which was prevented by a GluN2C/2D potentiator in wildtype and GluN2C heterozygous mice but not in GluN2C knockout mice. Together these results demonstrate a unique role of GluN2C subunit in schizophrenia-like behaviors.

A mouse model of seizures in anti-N-methyl-d-aspartate receptor encephalitis.

OBJECTIVE: Seizures develop in 80% of patients with anti-N-methyl-d-aspartate receptor (NMDAR) encephalitis, and these represent a major cause of morbidity and mortality. Anti-NMDAR antibodies have been linked to memory loss in encephalitis; however, their role in seizures has not been established. We determined whether anti-NMDAR antibodies from autoimmune encephalitis patients are pathogenic for seizures. METHODS: We performed continuous intracerebroventricular infusion of cerebrospinal fluid (CSF) or purified immunoglobulin (IgG) from the CSF of patients with anti-NMDAR encephalitis or polyclonal rabbit anti-NMDAR IgG, in male C57BL/6 mice. Seizure status during a 2-week treatment was assessed with video-electroencephalography. We assessed memory, anxiety-related behavior, and motor function at the end of treatment and assessed the extent of neuronal damage and gliosis in the CA1 region of hippocampus. We also performed whole-cell patch recordings from the CA1 pyramidal neurons in hippocampal slices of mice with seizures. RESULTS: Prolonged exposure to rabbit anti-NMDAR IgG, patient CSF, or human IgG purified from the CSF of patients with encephalitis induced seizures in 33 of 36 mice. The median number of seizures recorded in 2 weeks was 13, 39, and 35 per mouse in these groups, respectively. We observed only 18 brief nonconvulsive seizures in 11 of 29 control mice (median seizure count of 0) infused with vehicle (n = 4), normal CSF obtained from patients with noninflammatory central nervous system (CNS) conditions (n = 12), polyclonal rabbit IgG (n = 7), albumin (n = 3), and normal human IgG (n = 3). We did not observe memory deficits, anxiety-related behavior, or motor impairment measured at 2 weeks in animals treated with CSF from affected patients or rabbit IgG. Furthermore, there was no evidence of hippocampal cell loss or astrocyte proliferation in the same mice. SIGNIFICANCE: Our findings indicate that autoantibodies can induce seizures in anti-NMDAR encephalitis and offer a model for testing novel therapies for refractory autoimmune seizures.

Glutamate delta-1 receptor regulates cocaine-induced plasticity in the nucleus accumbens.

Cocaine exposure induces plasticity of glutamatergic synapses of medium spiny neurons (MSNs) in the nucleus accumbens (NAc), which has been proposed to contribute to its addictive behavior. The mechanisms underlying cocaine-induced plasticity are not fully understood. The orphan glutamate delta-1 (GluD1) receptor is a member of the ionotropic glutamate receptor family but does not function as a typical ligand-gated ion channel. Instead it serves a synaptogenic function by interacting with presynaptic Neurexin protein. Recent neuroanatomical studies have demonstrated enriched expression of GluD1 in the NAc but its role in reward behavior, MSN function, and drug-induced plasticity remains unknown. Using a combination of constitutive and conditional GluD1 KO models, we evaluated the effect of GluD1 ablation on cocaine-conditioned place preference (CPP) and cocaine-induced structural and functional plasticity. GluD1 KO mice showed higher cocaine CPP. Selective ablation of GluD1 from striatal neurons but not cortico-limbic excitatory neurons reproduced higher CPP. Higher cocaine preference in GluD1 KO correlated with an increase in spine density, greater maturation of dendritic spines, and basally upregulated spine-regulating active cofilin. GluD1 loss did not affect basal excitatory neurotransmission or plasticity but masked the generation of cocaine-induced silent synapses. Finally, loss of GluD1 increased the GluN2B subunit contribution to NMDA receptor currents in MSNs and a partial agonist of GluN2B-containing NMDA receptors normalized the higher active cofilin and cocaine preference in GluD1 KO mice. Together, these findings demonstrate a critical role of GluD1 in controlling susceptibility to cocaine preference and cocaine-induced plasticity by modulating NMDA receptor subunit contribution.

Region-specific Expression of NMDA Receptor GluN2C Subunit in Parvalbumin-Positive Neurons and Astrocytes: Analysis of GluN2C Expression using a Novel Reporter Model.

Hypofunction of NMDA receptors in parvalbumin (PV)-positive interneurons has been proposed as a potential mechanism for cortical abnormalities and symptoms in schizophrenia. GluN2C-containing receptors have been linked to this hypothesis due to the higher affinity of psychotomimetic doses of ketamine for GluN1/2C receptors. However, the precise cell-type expression of GluN2C subunit remains unknown. We describe the expression of the GluN2C subunit using a novel EGFP reporter model. We observed EGFP(GluN2C) localization in PV-positive neurons in the nucleus reticularis of the thalamus, globus pallidus externa and interna, ventral pallidum and substantia nigra. In contrast, EGFP(GluN2C)-expressing cells did not co-localize with PV-positive neurons in the cortex, striatum, hippocampus or amygdala. Instead, EGFP(GluN2C) expression in these regions co-localized with an astrocytic marker. We confirmed functional expression of GluN2C-containing receptors in the PV-neurons in substantia nigra and cortical astrocytes using electrophysiology. GluN2C was found to be enriched in several first-order and higher order thalamic nuclei. Interestingly, we found that a previous GluN2C ß-gal reporter model excluded expression from PV-neurons and certain thalamic nuclei but exhibited expression in the retrosplenial cortex. GluN2C's unique distribution in neuronal and non-neuronal cells in a brain region-specific manner raises interesting questions regarding the role of GluN2C-containing receptors in the central nervous system.

Arid1b haploinsufficiency disrupts cortical interneuron development and mouse behavior.

Haploinsufficiency of the AT-rich interactive domain 1B (ARID1B) gene causes autism spectrum disorder and intellectual disability; however, the neurobiological basis for this is unknown. Here we generated Arid1b-knockout mice and examined heterozygotes to model human patients. Arid1b-heterozygous mice showed a decreased number of cortical GABAergic interneurons and reduced proliferation of interneuron progenitors in the ganglionic eminence. Arid1b haploinsufficiency also led to an imbalance between excitatory and inhibitory synapses in the cerebral cortex. Furthermore, we found that Arid1b haploinsufficiency suppressed histone H3 lysine 9 acetylation (H3K9ac) overall and particularly reduced H3K9ac of the Pvalb promoter, resulting in decreased transcription. Arid1b-heterozygous mice exhibited abnormal cognitive and social behaviors, which were rescued by treatment with a positive allosteric GABAA receptor modulator. Our results demonstrate a critical role for Arid1b in interneuron development and behavior and provide insight into the pathogenesis of autism spectrum disorder and intellectual disability.

The NMDA receptor GluN2C subunit controls cortical excitatory-inhibitory balance, neuronal oscillations and cognitive function.

Despite strong evidence for NMDA receptor (NMDAR) hypofunction as an underlying factor for cognitive disorders, the precise roles of various NMDAR subtypes remains unknown. The GluN2C-containing NMDARs exhibit unique biophysical properties and expression pattern, and lower expression of GluN2C subunit has been reported in postmortem brains from schizophrenia patients. We found that loss of GluN2C subunit leads to a shift in cortical excitatory-inhibitory balance towards greater inhibition. Specifically, pyramidal neurons in the medial prefrontal cortex (mPFC) of GluN2C knockout mice have reduced mEPSC frequency and dendritic spine density and a contrasting higher frequency of mIPSCs. In addition a greater number of perisomatic GAD67 puncta was observed suggesting a potential increase in parvalbumin interneuron inputs. At a network level the GluN2C knockout mice were found to have a more robust increase in power of oscillations in response to NMDAR blocker MK-801. Furthermore, GluN2C heterozygous and knockout mice exhibited abnormalities in cognition and sensorimotor gating. Our results demonstrate that loss of GluN2C subunit leads to cortical excitatory-inhibitory imbalance and abnormal neuronal oscillations associated with neurodevelopmental disorders.

Anxiolytic effects of GLYX-13 in animal models of posttraumatic stress disorder-like behavior.

In the present study, we investigated the effectiveness of GLYX-13, an NMDA receptor glycine site functional partial agonist, to alleviate the enhanced anxiety and fear response in both a mouse and rat model of stress-induced behavioral changes that might be relevant to posttraumatic stress disorder (PTSD). Studies over the last decades have suggested that the hyperactivity of hypothalamic-pituitary-adrenal (HPA) axis is one of the most consistent findings in stress-related disease. Herein, we used these animal models to further investigate the effect of GLYX-13 on the stress hormone levels and glucocorticoid receptor (GR) expression. We found that exposure to foot shock induced long-lasting behavioral deficiencies in mice, including freezing and anxiety-like behaviors, that were significantly ameliorated by the long-term administration of GLYX-13 (5 or 10 mg/kg). Our enzyme-linked immunosorbent assay results showed that long-term administration of GLYX-13 at behaviorally effective doses (5 or 10 mg/kg) significantly decreased the elevated serum levels of both corticosterone and its upstream stress hormone adrenocorticotropic hormone in rats subjected to the TDS procedure. These results suggest that GLYX-13 exerts a therapeutic effect on PTSD-like stress responding that is accompanied by (or associated with) modulation of the HPA axis, including inhibition of stress hormone levels and upregulation of hippocampal GR expression.

Glutamate Delta-1 Receptor Regulates Metabotropic Glutamate Receptor 5 Signaling in the Hippocampus.

The delta family of ionotropic glutamate receptors consists of glutamate delta-1 (GluD1) and glutamate delta-2 receptors. We have previously shown that GluD1 knockout mice exhibit features of developmental delay, including impaired spine pruning and switch in the N-methyl-D-aspartate receptor subunit, which are relevant to autism and other neurodevelopmental disorders. Here, we identified a novel role of GluD1 in regulating metabotropic glutamate receptor 5 (mGlu5) signaling in the hippocampus. Immunohistochemical analysis demonstrated colocalization of mGlu5 with GluD1 punctas in the hippocampus. Additionally, GluD1 protein coimmunoprecipitated with mGlu5 in the hippocampal membrane fraction, as well as when overexpressed in human embryonic kidney 293 cells, demonstrating that GluD1 and mGlu5 may cooperate in a signaling complex. The interaction of mGlu5 with scaffold protein effector Homer, which regulates mechanistic target of rapamycin (mTOR) signaling, was abnormal both under basal conditions and in response to mGlu1/5 agonist (RS)-3,5-dihydroxyphenylglycine (DHPG) in GluD1 knockout mice. The basal levels of phosphorylated mTOR and protein kinase B, the signaling proteins downstream of mGlu5 activation, were higher in GluD1 knockout mice, and no further increase was induced by DHPG. We also observed higher basal protein translation and an absence of DHPG-induced increase in GluD1 knockout mice. In accordance with a role of mGlu5-mediated mTOR signaling in synaptic plasticity, DHPG-induced internalization of surface α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor subunits was impaired in the GluD1 knockout mice. These results demonstrate that GluD1 interacts with mGlu5, and loss of GluD1 impairs normal mGlu5 signaling potentially by dysregulating coupling to its effector. These studies identify a novel role of the enigmatic GluD1 subunit in hippocampal function.