Interaction of Endogenous Tau Protein with Synaptic Proteins Is Regulated by N-Methyl-D-aspartate Receptor-dependent Tau Phosphorylation

Amyloid-β and tau protein are the two most prominent factors in the pathology of Alzheimer disease. Recent studies indicate that phosphorylated tau might affect synaptic function. We now show that endogenous tau is found at postsynaptic sites where it interacts with the PSD95-NMDA receptor complex. NMDA receptor activation leads to a selective phosphorylation of specific sites in tau, regulating the interaction of tau with Fyn and the PSD95-NMDA receptor complex. Based on our results, we propose that the physiologically occurring phosphorylation of tau could serve as a regulatory mechanism to prevent NMDA receptor overexcitation.     

N-methyl-D-aspartate (NMDA) receptor composition modulates dendritic spine morphology in striatal medium spiny neurons

Dendritic spines of medium spiny neurons represent an essential site of information processing between NMDA and dopamine receptors in striatum. Even if activation of NMDA receptors in the striatum has important implications for synaptic plasticity and disease states, the contribution of specific NMDA receptor subunits still remains to be elucidated. Here, we show that treatment of corticostriatal slices with NR2A antagonist NVP-AAM077 or with NR2A blocking peptide induces a significant increase of spine head width. Sustained treatment with D1 receptor agonist (SKF38393) leads to a significant decrease of NR2A-containing NMDA receptors and to a concomitant increase of spine head width. Interestingly, co-treatment of corticostriatal slices with NR2A antagonist (NVP-AAM077) and D1 receptor agonist augmented the increase of dendritic spine head width as obtained with SKF38393. Conversely, NR2B antagonist (ifenprodil) blocked any morphological effect induced by D1 activation. These results indicate that alteration of NMDA receptor composition at the corticostriatal synapse contributes not only to the clinical features of disease states such as experimental parkinsonism but leads also to a functional and morphological outcome in dendritic spines of medium spiny neurons.     

Cytosolic Sulfotransferase 1A3 Is Induced by Dopamine and Protects Neuronal Cells from Dopamine Toxicity: ROLE OF D1 RECEPTOR-N-METHYL-d-ASPARTATE RECEPTOR COUPLING*

Dopamine neurotoxicity is associated with several neurodegenerative diseases, and neurons utilize several mechanisms, including uptake and metabolism, to protect them from injury. Metabolism of dopamine involves three enzymes: monoamine oxidase, catechol O-methyltransferase, and sulfotransferase. In primates but not lower order animals, a sulfotransferase (SULT1A3) is present that can rapidly metabolize dopamine to dopamine sulfate. Here, we show that SULT1A3 and a closely related protein SULT1A1 are highly inducible by dopamine. This involves activation of the D1 and NMDA receptors. Both ERK1/2 phosphorylation and calcineurin activation are required for induction. Pharmacological agents that inhibited induction or siRNA targeting SULT1A3 significantly increased the susceptibility of cells to dopamine toxicity. Taken together, these results show that dopamine can induce its own metabolism and protect neuron-like cells from damage, suggesting that SULT1A3 activity may be a risk factor for dopamine-dependent neurodegenerative diseases.     

Mechanism of AMPA receptor activation by partial agonists: disulfide trapping of closed lobe conformations

The mechanism by which agonist binding to an ionotropic glutamate receptor leads to channel opening is a central issue in molecular neurobiology. Partial agonists are useful tools for studying the activation mechanism because they produce full channel activation with lower probability than full agonists. Structural transitions that determine the efficacy of partial agonists can provide information on the trigger that begins the channel-opening process. The ligand-binding domain of AMPA receptors is a bilobed structure, and the closure of the lobes is associated with channel activation. One possibility is that partial agonists sterically block full lobe closure but that partial degrees of closure trigger the channel with a lower probability. Alternatively, full lobe closure may be required for activation, and the stability of the fully closed state could determine efficacy with the fully closed state having a lower stability when bound to partial relative to full agonists. Disulfide-trapping experiments demonstrated that even extremely low efficacy ligands such as 6-cyano-7-nitroquinoxaline-2,3-dione can produce a full lobe closure, presumably with low probability. The results are consistent the hypothesis that the efficacy is determined at least in part by the stability of the state in which the lobes are fully closed.     

Soluble oligomers of amyloid-β peptide disrupt membrane trafficking of α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor contributing to early synapse dysfunction

β-Amyloid (Aβ), a peptide generated from the amyloid precursor protein, is widely believed to underlie the pathophysiology of Alzheimer disease (AD). Emerging evidences suggest that soluble Aβ oligomers adversely affect synaptic function, leading to cognitive failure associated with AD. The Aβ-induced synaptic dysfunction has been attributed to the synaptic removal of α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptors (AMPARs). However, the molecular mechanisms underlying the loss of AMPAR induced by Aβ at synapses are largely unknown. In this study we have examined the effect of Aβ oligomers on phosphorylated GluA1 at serine 845, a residue that plays an essential role in the trafficking of AMPARs toward extrasynaptic sites and the subsequent delivery to synapses during synaptic plasticity events. We found that Aβ oligomers reduce basal levels of Ser-845 phosphorylation and surface expression of AMPARs affecting AMPAR subunit composition. Aβ-induced GluA1 dephosphorylation and reduced receptor surface levels are mediated by an increase in calcium influx into neurons through ionotropic glutamate receptors and activation of the calcium-dependent phosphatase calcineurin. Moreover, Aβ oligomers block the extrasynaptic delivery of AMPARs induced by chemical synaptic potentiation. In addition, reduced levels of total and phosphorylated GluA1 are associated with initial spatial memory deficits in a transgenic mouse model of AD. These findings indicate that Aβ oligomers could act as a synaptic depressor affecting the mechanisms involved in the targeting of AMPARs to the synapses during early stages of the disease.     

Restoration of Glutamatergic Transmission by Dopamine D4 Receptors in Stressed Animals

The prefrontal cortex (PFC), a key brain region for cognitive and emotional processes, is highly regulated by dopaminergic inputs. The dopamine D₄ receptor, which is enriched in PFC, has been implicated in mental disorders, such as attention deficit-hyperactivity disorder and schizophrenia. Recently we have found homeostatic regulation of AMPA receptor-mediated synaptic transmission in PFC pyramidal neurons by the D₄ receptor, providing a potential mechanism for D₄ in stabilizing cortical excitability. Because stress is tightly linked to adaptive and maladaptive changes associated with mental health and disorders, we examined the synaptic actions of D₄ in stressed rats. We found that neural excitability was elevated by acute stress and dampened by repeated stress. D₄ activation produced a potent reduction of excitatory transmission in acutely stressed animals and a marked increase of excitatory transmission in repeatedly stressed animals. These effects of D₄ targeted GluA2-lacking AMPA receptors and relied on the bi-directional regulation of calcium/calmodulin kinase II activity. The restoration of PFC glutamatergic transmission in stress conditions may enable D₄ receptors to serve as a synaptic stabilizer in normal and pathological conditions.     

Regulation of N-methyl-D-aspartic acid (NMDA) receptors by metabotropic glutamate receptor 7

Emerging evidence suggests that metabotropic glutamate receptors (mGluRs) are potential novel targets for brain disorders associated with the dysfunction of prefrontal cortex (PFC), a region critical for cognitive and emotional processes. Because N-methyl-D-aspartic acid receptor (NMDAR) dysregulation has been strongly associated with the pathophysiology of mental illnesses, we examined the possibility that mGluRs might be involved in modulating PFC functions by targeting postsynaptic NMDARs. We found that application of prototypical group III mGluR agonists significantly reduced NMDAR-mediated synaptic and ionic currents in PFC pyramidal neurons, which was mediated by mGluR7 localized at postsynaptic neurons and involved the β-arrestin/ERK signaling pathway. The mGluR7 modulation of NMDAR currents was prevented by agents perturbing actin dynamics and by the inhibitor of cofilin, a major actin-depolymerizing factor. Consistently, biochemical and immunocytochemical results demonstrated that mGluR7 activation increased cofilin activity and F-actin depolymerization via an ERK-dependent mechanism. Furthermore, mGluR7 reduced the association of NMDARs with the scaffolding protein PSD-95 and the surface level of NMDARs in an actin-dependent manner. These data suggest that mGluR7, by affecting the cofilin/actin signaling, regulates NMDAR trafficking and function. Because ablation of mGluR7 leads to a variety of behavioral symptoms related to PFC dysfunction, such as impaired working memory and reduced anxiety and depression, our results provide a potential mechanism for understanding the role of mGluR7 in mental health and disorders.     

Dynamics of Cleft Closure of the GluA2 Ligand-binding Domain in the Presence of Full and Partial Agonists Revealed by Hydrogen-Deuterium Exchange

The majority of excitatory neurotransmission in the CNS is mediated by tetrameric AMPA receptors. Channel activation begins with a series of interactions with an agonist that binds to the cleft between the two lobes of the ligand-binding domain of each subunit. Binding leads to a series of conformational transitions, including the closure of the two lobes of the binding domain around the ligand, culminating in ion channel opening. Although a great deal has been learned from crystal structures, determining the molecular details of channel activation, deactivation, and desensitization requires measures of dynamics and stabilities of hydrogen bonds that stabilize cleft closure. The use of hydrogen-deuterium exchange at low pH provides a measure of the variation of stability of specific hydrogen bonds among agonists of different efficacy. Here, we used NMR measurements of hydrogen-deuterium exchange to determine the stability of hydrogen bonds in the GluA2 (AMPA receptor) ligand-binding domain in the presence of several full and partial agonists. The results suggest that the stabilization of hydrogen bonds between the two lobes of the binding domain is weaker for partial than for full agonists, and efficacy is correlated with the stability of these hydrogen bonds. The closure of the lobes around the agonists leads to a destabilization of the hydrogen bonding in another portion of the lobe interface, and removing an electrostatic interaction in Lobe 2 can relieve the strain. These results provide new details of transitions in the binding domain that are associated with channel activation and desensitization.     

Sustained Glutamate Receptor Activation Down-regulates GABAB Receptors by Shifting the Balance from Recycling to Lysosomal Degradation

Metabotropic GABA_B receptors are abundantly expressed at glutamatergic synapses where they control excitability of the synapse. Here, we tested the hypothesis that glutamatergic neurotransmission may regulate GABA_B receptors. We found that application of glutamate to cultured cortical neurons led to rapid down-regulation of GABA_B receptors via lysosomal degradation. This effect was mimicked by selective activation of AMPA receptors and further accelerated by coactivation of group I metabotropic glutamate receptors. Inhibition of NMDA receptors, blockade of L-type Ca²⁺ channels, and removal of extracellular Ca²⁺ prevented glutamate-induced down-regulation of GABA_B receptors, indicating that Ca²⁺ influx plays a critical role. We further established that glutamate-induced down-regulation depends on the internalization of GABA_B receptors. Glutamate did not affect the rate of GABA_B receptor endocytosis but led to reduced recycling of the receptors back to the plasma membrane. Blockade of lysosomal activity rescued receptor recycling, indicating that glutamate redirects GABA_B receptors from the recycling to the degradation pathway. In conclusion, the data indicate that sustained activation of AMPA receptors down-regulates GABA_B receptors by sorting endocytosed GABA_B receptors preferentially to lysosomes for degradation on the expense of recycling. This mechanism may relieve glutamatergic synapses from GABA_B receptor-mediated inhibition resulting in increased synaptic excitability.     

The WD40-repeat Proteins WDR-20 and WDR-48 Bind and Activate the Deubiquitinating Enzyme USP-46 to Promote the Abundance of the Glutamate Receptor GLR-1 in the Ventral Nerve Cord of Caenorhabditis elegans

Ubiquitin-mediated endocytosis and degradation of glutamate receptors controls their synaptic abundance and is implicated in modulating synaptic strength. The deubiquitinating enzymes (DUBs) that function in the nervous system are beginning to be defined, but the mechanisms that control DUB activity in vivo are understood poorly. We found previously that the DUB USP-46 deubiquitinates the Caenorhabditis elegans glutamate receptor GLR-1 and prevents its degradation in the lysosome. The WD40-repeat (WDR) proteins WDR20 and WDR48/UAF1 have been shown to bind to USP46 and stimulate its catalytic activity in other systems. Here we identify the C. elegans homologs of these WDR proteins and show that C. elegans WDR-20 and WDR-48 can bind and stimulate USP-46 catalytic activity in vitro. Overexpression of these activator proteins in vivo increases the abundance of GLR-1 in the ventral nerve cord, and this effect is further enhanced by coexpression of USP-46. Biochemical characterization indicates that this increase in GLR-1 abundance correlates with decreased levels of ubiquitin-GLR-1 conjugates, suggesting that WDR-20, WDR-48, and USP-46 function together to deubiquitinate and stabilize GLR-1 in neurons. Overexpression of WDR-20 and WDR-48 results in alterations in locomotion behavior consistent with increased glutamatergic signaling, and this effect is blocked in usp-46 loss-of-function mutants. Conversely, wdr-20 and wdr-48 loss-of-function mutants exhibit changes in locomotion behavior that are consistent with decreased glutamatergic signaling. We propose that WDR-20 and WDR-48 form a complex with USP-46 and stimulate the DUB to deubiquitinate and stabilize GLR-1 in vivo.     

Cellular mechanisms for dopamine D4 receptor-induced homeostatic regulation of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors

Aberrant dopamine D(4) receptor function has been implicated in mental illnesses, including schizophrenia and attention deficit-hyperactivity disorder. Recently we have found that D(4) receptor exerts an activity-dependent bi-directional regulation of AMPA receptor (AMPAR)-mediated synaptic currents in pyramidal neurons of prefrontal cortex (PFC) via the dual control of calcium/calmodulin kinase II (CaMKII) activity. In this study, we examined the signaling mechanisms downstream of CaMKII that govern the complex effects of D(4) on glutamatergic transmission. We found that in PFC neurons at high activity state, D(4) suppresses AMPAR responses by disrupting the kinesin motor-based transport of GluR2 along microtubules, which was accompanied by the D(4) reduction of microtubule stability via a mechanism dependent on CaMKII inhibition. On the other hand, in PFC neurons at the low activity state, D(4) potentiates AMPAR responses by facilitating synaptic targeting of GluR1 through the scaffold protein SAP97 via a mechanism dependent on CaMKII stimulation. Taken together, these results have identified distinct signaling mechanisms underlying the homeostatic regulation of glutamatergic transmission by D(4) receptors, which may be important for cognitive and emotional processes in which dopamine is involved.     

Importance of Shank3 protein in regulating metabotropic glutamate receptor 5 (mGluR5) expression and signaling at synapses

Shank3/PROSAP2 gene mutations are associated with cognitive impairment ranging from mental retardation to autism. Shank3 is a large scaffold postsynaptic density protein implicated in dendritic spines and synapse formation; however, its specific functions have not been clearly demonstrated. We have used RNAi to knockdown Shank3 expression in neuronal cultures and showed that this treatment specifically reduced the synaptic expression of the metabotropic glutamate receptor 5 (mGluR5), but did not affect the expression of other major synaptic proteins. The functional consequence of Shank3 RNAi knockdown was impaired signaling via mGluR5, as shown by reduction in ERK1/2 and CREB phosphorylation induced by stimulation with (S)-3,5-dihydroxyphenylglycine (DHPG) as the agonist of mGluR5 receptors, impaired mGluR5-dependent synaptic plasticity (DHPG-induced long-term depression), and impaired mGluR5-dependent modulation of neural network activity. We also found morphological abnormalities in the structure of synapses (spine number, width, and length) and impaired glutamatergic synaptic transmission, as shown by reduction in the frequency of miniature excitatory postsynaptic currents (mEPSC). Notably, pharmacological augmentation of mGluR5 activity using 3-cyano-N-(1,3-diphenyl-1H-pyrazol-5-yl)-benzamide as the positive allosteric modulator of these receptors restored mGluR5-dependent signaling (DHPG-induced phosphorylation of ERK1/2) and normalized the frequency of mEPSCs in Shank3-knocked down neurons. These data demonstrate that a deficit in mGluR5-mediated intracellular signaling in Shank3 knockdown neurons can be compensated by 3-cyano-N-(1,3-diphenyl-1H-pyrazol-5-yl)-benzamide; this raises the possibility that pharmacological augmentation of mGluR5 activity represents a possible new therapeutic approach for patients with Shank3 mutations.     

Protein kinase C promotes N-methyl-D-aspartate (NMDA) receptor trafficking by indirectly triggering calcium/calmodulin-dependent protein kinase II (CaMKII) autophosphorylation

Regulation of neuronal NMDA receptor (NMDAR) is critical in synaptic transmission and plasticity. Protein kinase C (PKC) promotes NMDAR trafficking to the cell surface via interaction with NMDAR-associated proteins (NAPs). Little is known, however, about the NAPs that are critical to PKC-induced NMDAR trafficking. Here, we showed that calcium/calmodulin-dependent protein kinase II (CaMKII) could be a NAP that mediates the potentiation of NMDAR trafficking by PKC. PKC activation promoted the level of autophosphorylated CaMKII and increased association with NMDARs, accompanied by functional NMDAR insertion, at postsynaptic sites. This potentiation, along with PKC-induced long term potentiation of the AMPA receptor-mediated response, was abolished by CaMKII antagonist or by disturbing the interaction between CaMKII and NR2A or NR2B. Further mutual occlusion experiments demonstrated that PKC and CaMKII share a common signaling pathway in the potentiation of NMDAR trafficking and long-term potentiation (LTP) induction. Our results revealed that PKC promotes NMDA receptor trafficking and induces synaptic plasticity through indirectly triggering CaMKII autophosphorylation and subsequent increased association with NMDARs.     

Impaired alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor trafficking and function by mutant huntingtin

Emerging evidence from studies of Huntington disease (HD) pathophysiology suggests that huntingtin (htt) and its associated protein HAP1 participate in intracellular trafficking and synaptic function. However, it is largely unknown whether AMPA receptor trafficking, which is crucial for controlling the efficacy of synaptic excitation, is affected by the mutant huntingtin with polyglutamine expansion (polyQ-htt). In this study, we found that expressing polyQ-htt in neuronal cultures significantly decreased the amplitude and frequency of AMPAR-mediated miniature excitatory postsynaptic current (mEPSC), while expressing wild-type huntingtin (WT-htt) increased mEPSC. AMPAR-mediated synaptic transmission was also impaired in a transgenic mouse model of HD expressing polyQ-htt. The effect of polyQ-htt on mEPSC was mimicked by knockdown of HAP1 and occluded by the dominant negative HAP1. Moreover, we found that huntingtin affected mESPC via a mechanism depending on the kinesin motor protein, KIF5, which controls the transport of GluR2-containing AMPARs along microtubules in dendrites. The GluR2/KIF5/HAP1 complex was disrupted and dissociated from microtubules in the HD mouse model. Together, these data suggest that AMPAR trafficking and function is impaired by mutant huntingtin, presumably due to the interference of KIF5-mediated microtubule-based transport of AMPA receptors. The diminished strength of glutamatergic transmission could contribute to the deficits in movement control and cognitive processes in HD conditions.     

Potent and selective inhibition of a single alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunit by an RNA aptamer

Inhibitors of AMPA-type glutamate ion channels are useful as biochemical probes for structure-function studies and as drug candidates for a number of neurological disorders and diseases. Here, we describe the identification of an RNA inhibitor or aptamer by an in vitro evolution approach and a characterization of its mechanism of inhibition on the sites of interaction by equilibrium binding and on the receptor channel opening rate by a laser-pulse photolysis technique. Our results show that the aptamer is a noncompetitive inhibitor that selectively inhibits the GluA2Q(flip) AMPA receptor subunit without any effect on other AMPA receptor subunits or kainate or NMDA receptors. On the GluA2 subunit, this aptamer preferentially inhibits the flip variant. Furthermore, the aptamer preferentially inhibits the closed-channel state of GluA2Q(flip) with a K(I) = 1.5 μM or by ～15-fold over the open-channel state. The potency and selectivity of this aptamer rival those of small molecule inhibitors. Together, these properties make this aptamer a promising candidate for the development of water-soluble, highly potent, and GluA2 subunit-selective drugs.     

N-methyl-D-aspartate receptor mechanosensitivity is governed by C terminus of NR2B subunit

N-methyl-D-aspartate receptors (NMDARs), critical mediators of both physiologic and pathologic neurological signaling, have previously been shown to be sensitive to mechanical stretch through the loss of its native Mg(2+) block. However, the regulation of this mechanosensitivity has yet to be further explored. Furthermore, as it has become apparent that NMDAR-mediated signaling is dependent on specific NMDAR subtypes, as governed by the identity of the NR2 subunit, a crucial unanswered question is the role of subunit composition in observed NMDAR mechanosensitivity. Here, we used a recombinant system to assess the mechanosensitivity of specific subtypes and demonstrate that the mechanosensitive property is uniquely governed by the NR2B subunit. NR1/NR2B NMDARs displayed significant stretch sensitivity, whereas NR1/NR2A NMDARs did not respond to stretch. Furthermore, NR2B mechanosensitivity was regulated by PKC activity, because PKC inhibition reduced stretch responses in transfected HEK 293 cells and primary cortical neurons. Finally, using NR2B point mutations, we identified a PKC phosphorylation site, Ser-1323 on NR2B, as a unique critical regulator of stretch sensitivity. These data suggest that the selective mechanosensitivity of NR2B can significantly impact neuronal response to traumatic brain injury and illustrate that the mechanical tone of the neuron can be dynamically regulated by PKC activity.     

Characterization of a central Ca2+/calmodulin-dependent protein kinase IIalpha/beta binding domain in densin that selectively modulates glutamate receptor subunit phosphorylation

The densin C-terminal domain can target Ca(2+)/calmodulin-dependent protein kinase IIα (CaMKIIα) in cells. Although the C-terminal domain selectively binds CaMKIIα in vitro, full-length densin associates with CaMKIIα or CaMKIIβ in brain extracts and in transfected HEK293 cells. This interaction requires a second central CaMKII binding site, the densin-IN domain, and an "open" activated CaMKII conformation caused by Ca(2+)/calmodulin binding, autophosphorylation at Thr-286/287, or mutation of Thr-286/287 to Asp. Mutations in the densin-IN domain (L815E) or in the CaMKIIα/β catalytic domain (I205/206K) disrupt the interaction. The amino acid sequence of the densin-IN domain is similar to the CaMKII inhibitor protein, CaMKIIN, and a CaMKIIN peptide competitively blocks CaMKII binding to densin. CaMKII is inhibited by both CaMKIIN and the densin-IN domain, but the inhibition by densin is substrate-selective. Phosphorylation of a model peptide substrate, syntide-2, or of Ser-831 in AMPA receptor GluA1 subunits is fully inhibited by densin. However, CaMKII phosphorylation of Ser-1303 in NMDA receptor GluN2B subunits is not effectively inhibited by densin in vitro or in intact cells. Thus, densin can target multiple CaMKII isoforms to differentially modulate phosphorylation of physiologically relevant downstream targets.     

Key amino acid residues within the third membrane domains of NR1 and NR2 subunits contribute to the regulation of the surface delivery of N-methyl-D-aspartate receptors

N-methyl-d-aspartate (NMDA) receptors are glutamate ionotropic receptors that play critical roles in synaptic transmission, plasticity, and excitotoxicity. The functional NMDA receptors, heterotetramers composed mainly of two NR1 and two NR2 subunits, likely pass endoplasmic reticulum quality control before they are released from the endoplasmic reticulum and trafficked to the cell surface. However, the mechanism underlying this process is not clear. Using truncated and mutated NMDA receptor subunits expressed in heterologous cells, we found that the M3 domains of both NR1 and NR2 subunits contain key amino acid residues that contribute to the regulation of the number of surface functional NMDA receptors. These key residues are critical neither for the interaction between the NR1 and NR2 subunits nor for the formation of the functional receptors, but rather they regulate the early trafficking of the receptors. We also found that the identified key amino acid residues within both NR1 and NR2 M3 domains contribute to the regulation of the surface expression of unassembled NR1 and NR2 subunits. Thus, our data identify the unique role of the membrane domains in the regulation of the number of surface NMDA receptors.     

海马多巴胺D1受体激活抑制谷氨酸介导的大鼠慢性应激性抑郁

本文旨在探讨在慢性应激性抑郁发生过程中多巴胺D1受体对谷氨酸及其离子型受体的影响。实验通过建立慢性不可预见性温和应激(chronic unpredictable mild stress,CUMS)抑郁模型,结合海马微量注射多巴胺D1受体激动剂SKF38393、非竞争性N-甲基-D-天冬氨酸(N-methyl-D-aspartic acid,NMDA)受体拮抗剂MK-801和α-氨基羟甲基异恶唑丙酸(α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid,AMPA)受体的拮抗剂NBQX,运用糖水偏爱测试、旷场实验和悬尾实验等方法检测动物的行为表现,采用高效液相色谱法(high-performance liquid chromatography,HPLC)和Western blot实验来检测海马内谷氨酸含量及其离子型受体关键亚基的表达。结果显示,与对照组相比,CUMS组大鼠表现出明显的抑郁样行为变化,且海马谷氨酸含量升高,其NMDA受体的NR1亚基与AMPA受体的GluR2/3亚基也明显下调;注射SKF38393后可明显改善应激引起的抑郁样行为,且海马谷氨酸含量显...