AMPA Receptor Subunit GluR1 Research Articles

Effect of propofol post-conditioning on expression of GluR1-containing AMPA receptors during cerebral ischemia-reperfusion injury in rats

Objective To evaluate the effect of propofol post-conditioning on the expression of GluR1-containing AMPA receptors during cerebral ischemia-reperfusion (I/R) injury in rats. Methods Sixty-four healthy male Sprague-Dawley rats, aged 7-8 weeks, weighing 250-280 g, were randomly divided into 3 groups (n = 18 each) using a random number table: sham operation group (group S), I/R group and propofol group (group P). Focal cerebral ischemia was induced by occlusion of the middle cerebral artery for 1 h followed by reperfusion in I/R and P groups. Propofol was infused at 20 mg·kg-1·h-1 for 2 h starting from the onset of reperfusion in group P, and the equal volume of normal saline was given in S and I/R groups. Fear conditioning test was performed on 7, 14 and 28 days after operation. The time spent freezing induced by context and condition was recorded, and the percentage was calculated. The modified neurological deficit score (NDS) was measured at 24 h of infusion. The cerebral infarct size was measured by TTC. The hippocampal samples were isolated for determination of the expression of protein kinase A (PKA), A-kinase anchoring protein 150(AKAP150) and AMPA receptor GluR1 subunit and phosphorylation of GluR1 at serine 845(Ser845) site (pGluR1 Ser845). Results Compared with group S, the NDS and cerebral infarct size were significantly increased, the expression of PKA and pGluR1 Ser845 was down-regulated, and the percentage of time spent freezing induced by context and condition was decreased on 7 and 14 days after operation in I/R and P groups. Compared with group I/R, the NDS and cerebral infarct size were significantly decreased, the expression of PKA and pGluR1 Ser845 was up-regulated, and the percentage of time spent freezing induced by context and condition was increased on 7 and 14 days after operation in group P. Conclusion The mechanism by which propofol postconditioning reduces cerebral I/R injury is related to phosphorylation of AMPA receptor GluR1 subunit in rats. Key words: Propofol; Brain; Reperfusion injury; Receptors, AMPA

Blocking GluR2-GAPDH ameliorates experimental autoimmune encephalomyelitis.

ObjectiveMultiple sclerosis (MS) is the most common disabling neurological disease of young adults. The pathophysiological mechanism of MS remains largely unknown and no cure is available. Current clinical treatments for MS modulate the immune system, with the rationale that autoimmunity is at the core of MS pathophysiology.MethodsExperimental autoimmune encephalitis (EAE) was induced in mice with MOG35-55 and clinical scoring was performed to monitor signs of paralysis. EAE mice were injected intraperitoneally with TAT-fusion peptides daily from day 10 until day 30 after immunization, and their effects were measured at day 17 or day 30.ResultsWe report a novel target for the development of MS therapy, which aimed at blocking glutamate-mediated neurotoxicity through targeting the interaction between the AMPA (2-amino-3-(3-hydroxy-5-methyl-isoxazol-4-yl) propanoic acid) receptor and an interacting protein. We found that protein complex composed of the GluR2 subunit of AMPA receptors and GAPDH (glyceraldehyde-3-phosphate dehydrogenase) was present at significantly higher levels in postmortem tissue from MS patients and in EAE mice, an animal model for MS. Next, we developed a peptide that specifically disrupts the GluR2 -GAPDH complex. This peptide greatly improves neurological function in EAE mice, reduces neuron death, rescues demyelination, increases oligodendrocyte survival, and reduces axonal damage in the spinal cords of EAE mice. More importantly, our peptide has no direct suppressive effect on naive T-cell responses or basal neurotransmission.InterpretationThe GluR2 -GAPDH complex represents a novel therapeutic target for the development of medications for MS that work through a different mechanism than existing treatments.

Age-Related Decrease in Glucagon-Like Peptide-1 in Mouse Prefrontal Cortex but Not in Hippocampus Despite the Preservation of Its Receptor

Glucagon-like peptide-1 receptor (GLP-1R) agonist treatment has the potential to be a novel therapeutic treatment for Alzheimer’s disease (AD). We previously reported that exendin-4, a Gαs protein-coupled GLP-1R agonist, up-regulates the membrane AMPA receptor GluR1 subunit in the neocortex. However, it is uncertain whether GLP-1R agonists have an advantage as an AD treatment target compared with other Gαs protein-coupled receptors. Here we show that both the protein level of proglucagon, a precursor of GLP-1, and the immunoreactivity level of GLP-1 are significantly decreased in the medial prefrontal cortex (mPFC) of aged mice (14 months old) compared with young (3 weeks old) or adult (6 months old) mice, but not in area CA1, the dentate gyrus (DG) nor in the nucleus of the solitary tract. However, the protein and immunoreactivity levels of GLP-1R in the mPFC, DG and hippocampal CA1 and CA3 areas were preserved in the aged mice. We then confirmed whether the age-dependent decrease in GLP-1 in the mPFC was associated with the activity level or the number of microglial cells in the mPFC. Co-staining of CD11b and GLP-1 in the mPFC revealed that the number of CD11b-positive cells was increased in the aged mice. Moreover, lipopolysaccharide (LPS) injection increased the number of CD11b-positive cells in the mPFC, but the number of GLP-1-positive cells was unchanged. However, the number of CD11b-positive cells that co-localized with GLP-1R in the mPFC is increased by LPS and aging. Because the GLP-1R is preserved in aged mPFC, but the amount of GLP-1 produced in the brain region is diminished, and spatial cognitive memory was impaired in aged mice, we propose that treatment with GLP-1 analogues has great promise for rescuing and ameliorating the age-related mPFC-dependent decline of cognitive functions.

Insulin induces phosphorylation of the AMPA receptor subunit GluR1, reversed by ZIP, and over‐expression of Protein Kinase M zeta, reversed by amyloid beta

Insulin receptor (IR) in the brain plays a role in synaptic plasticity and cognitive functions. Phosphorylation of α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptors GluR1 subunit at Serine 831 is regulated by calcium-calmodulin-dependent protein kinase II and protein kinase C that underlie long-term potentiation and learning/memory. Recent studies have shown that the novel Protein Kinase M zeta (PKMζ) underlies synaptic plasticity and may regulate AMPAr. In this study, we show that insulin induces phosphorylation of Serine 831 GluR1 subunit of AMPAr and induces over-expression of PKMζ; pre-treatment with either the IR inhibitor 3-Bromo-5-t-butyl-4-hydroxy-benzylidenemalonitrile (AG1024) or PKMζ inhibitor protein kinase C zeta pseudo-substrate inhibitor returned the phosphorylation value of GluR1 to control level. Amyloid beta (Aβ) peptide in the form of oligomers interferes with IR signaling. Pre-treating neuronal cultures with Aβ following incubation with insulin, we found a reduction of insulin-dependent PKMζ over-expression and MAPK/Erk (1/2) phosphorylation, i.e., signaling pathways involved in synaptic plasticity and learning/memory. These results indicate a new intracellular insulin signaling pathway, and, additionally, that insulin resistance in Alzheimer's disease is a response to the production and accumulation of Aβ.

P.6.a.007 The role of glutamatergic receptors within the dopaminergic reinforcement system in alcohol-dependent phenotypes

Of the ionotropic glutamatergic receptors, the NMDA receptor is clearly implicated in the acute and chronic effects of ethanol; however, the role of the AMPA receptor in mediating the effects of ethanol in vivo is as yet unclear. Using mice deficient in the AMPA receptor subunit GluR1 (GluR1−/− mice), we investigated whether the AMPA receptor had a significant role in mediating the effects of ethanol. GluR1−/− mice showed greater locomotor activity in a novel environment, but by the fifth day of repeated testing their activity was the same as that of wild-type mice. In contrast to their enhanced locomotor activity, on an accelerating rotarod GluR1−/− mice performed consistently worse than wild-types. With regard to the effects of ethanol on motor responses, GluR1−/− mice did not differ significantly from wild-type mice in ethanol’s sedative or incoordinating effects. However, the GluR1−/− mice were insensitive to the hypothermic effects of a hypnotic dose of ethanol in contrast to wild-types; this effect was dissociable from the hypnotic effects of ethanol. Further, tolerance to ethanol developed equally for GluR1−/− mice versus wild-type mice. In terms of alcohol drinking behavior, compared to wild-types, GluR1−/− mice differed neither in the acquisition of voluntary ethanol consumption nor in stress-induced ethanol drinking, nor in the expression of an alcohol deprivation effect (ADE) which is used as a model of relapse-like drinking behavior. In summary, although the loss of a hypothermic effect of ethanol in GluR1−/− mice indicates a critical role for the AMPA receptors in this effect, the GluR1 subunit of the AMPA receptor does not seem to play a critical role in the etiology of alcohol dependence. However, changes observed in activity patterns may be related to the putative role of AMPA receptors in attention deficit hyperactivity disorder.

Deletion of olfactomedin 2 induces changes in the AMPA receptor complex and impairs visual, olfactory, and motor functions in mice

Olfactomedin 2 (Olfm2) is a secretory glycoprotein belonging to the family of olfactomedin domain-containing proteins. A previous study has shown that a mutation in OLFM2 is associated with primary open angle glaucoma in Japanese patients. In the present study, we generated Olfm2 deficient mice by replacing the Olfm2 gene with the LacZ gene. The loss of Olfm2 resulted in no gross abnormalities. However, Olfm2 null mice showed reduced exploration, locomotion, olfactory sensitivity, abnormal motor coordination, and anxiety related behavior. The pattern of the Olfm2 gene expression was studied in the brain and eye using β-galactosidase staining. In the brain, Olfm2 was mainly expressed in the olfactory bulb, cortex, piriform cortex, olfactory trabeculae, and inferior and superior colliculus. In the eye expression was detected mainly in retinal ganglion cells. In Olfm2 null mice, the amplitude of the first negative wave in the visual evoked potential test was significantly reduced as compared with wild-type littermates. Olfm2, similar to Olfm1, interacted with the GluR2 subunit of the AMPAR complexes and Olfm2 co-segregated with the AMPA receptor subunit GluR2 and other synaptic proteins in the synaptosomal membrane fraction upon biochemical fractionation of the adult mice cortex and retina. Immunoprecipitation from the synaptosomal membrane fraction of the Olfm2 null mouse brain cortex using the GluR2 antibody showed reduced levels of several components of the AMPAR complex in the immunoprecipitates including Olfm1, PSD95 and CNIH2. These results suggest that heterodimers of Olfm1 and Olfm2 interact with AMPAR more efficiently than Olfm2 homodimers and that Olfm2 plays a role in the organization of the AMPA receptor complexes.

Ионотропные AMPA рецепторы глутамата в патогенезе симптоматической эпилепсии при глиомах полушарий головного мозга

The purpose of the research is to study the role of AMPA receptors of glutamate in the mechanisms of the development of epi-lepsy in the patients with gliomas of the big hemispheres of a brain. Materials and methods: 92 patients with gliomas of the big hemispheres of a brain have been examined. Immune enzyme method of semi-quantitative determination of the level of auto-antibodies to NR2A subunit of NMDA and GluR1 subunit of AMPA receptors of glutamate was used. Results: The frequency and clinical features of symptomatic epilepsy have been studied. The reaction of NMDA and of AMPA receptors of glutamate depending on localization and degree of malignance and features of clinical course of the disease, have been examined. Conclusion: A high-technology of patho-morphological research of brain tumors made in recent years has revealed that glial tumors start releasing glutamate by themselves, as their anaplasia level increases, which causes exitotoxical effect in anatomical lines of peritumoral area. Such blastomastoma growth features form specificity of clinical aspect of disease, including epileptic syndrome. It is shown dominative increase the level of auto-antibodies to GluR1 subunit of AMPA receptors of glutamate in the patients with gliomas, current with epileptic syndrome. Under the effect of the tumor on the frontal and temporal share the maximum level of autoantibodies, mainly to GluR1 subunit of AMPA receptors of glutamate is registered.

Аlterationdegree of NMDA and AMPA receptors of glutamate in the pathogenesis of the disease and technological peculiarities of surgical treatment of the hemispheric glioma-swith the epileptic syndrome

The development of effective approaches to the treatment of patients with symptomatic tumor epilepsy was determined by the level of our fundamental knowledge of the basic mechanisms of epileptogenesis on cellular and molecular level. 92 patients with gliomas of the cerebral hemisphereswere examined. Immunoenzyme method ofsemiquantitative determination of the level of autoantibodies to NR2A subunit of NMDA and GluR1 subunit of AMPA receptors of glutamate was used. The reaction of NMDA and AMPA glutamate receptors depending on the availability of an epileptic syndrome in the clinical picture of the disease and the extent of radical surgery has been studied. Pre-emptive increase of the level of autoantibodies to GluR1 subunit of AMPA receptors of glutamate in patients with hemispheric gliomaswith epileptic syndrome was demonstrated. It was foundonly the total removal of the tumor reduced significantly the level of autoantibodies to ionotropic glutamate receptors.

Measuring the Liquidity of ETFs: An Application to the European Market

We have used site-directed mutagenesis of amino acids located within the S1 and S2 ligand binding domains of the NR2A <i>N</i>-methyl-d-aspartate (NMDA) receptor subunit to explore the nature of ligand binding. Wild-type or mutated NR1/NR2A NMDA receptors were expressed in <i>Xenopus laevis</i> oocytes and studied using two electrode voltage clamp. We investigated the effects of mutations in the S1 and S2 regions on the potencies of the agonists l-glutamate, l-aspartate, (<i>R</i>,<i>S</i>)-tetrazol-5yl-glycine, and NMDA. Mutation of each of the corresponding residues found in the NR2A receptor subunit, suggested to be contact residues in the GluR2 α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunit, caused a rightward shift in the concentration-response curve for each agonist examined. None of the mutations examined altered the efficacy of glutamate as assessed by methanethiosulfonate ethylammonium potentiation of agonist-evoked currents. In addition, none of the mutations altered the potency of glycine. Homology modeling and molecular dynamics were used to evaluate molecular details of ligand binding of both wild-type and mutant receptors, as well as to explore potential explanations for agonist selectivity between glutamate receptor subtypes. The modeling studies support our interpretation of the mutagenesis data and indicate a similar binding strategy for l-glutamate and NMDA when they occupy the binding site in NMDA receptors, as has been proposed for glutamate binding to the GluR2 AMPA receptor subunit. Furthermore, we offer an explanation as to why “charge conserving” mutations of two residues in the binding pocket result in nonfunctional receptor channels and suggest a contributing molecular determinant for why NMDA is not an agonist at AMPA receptors.

Exendin-4 promotes the membrane trafficking of the AMPA receptor GluR1 subunit and ADAM10 in the mouse neocortex

Glucagon-like peptide-1 (GLP-1) is a novel treatment modality for type 2 diabetes mellitus. However, GLP-1 has been suggested as a therapeutic target for Alzheimer's disease (AD). In rodent studies, GLP-1 reduces amyloid beta (Aβ) and facilitates synaptic plasticity. Therefore, in the present study, we investigated how GLP-1 facilitates synaptic plasticity and reduces the Aβ in vivo. Exendin-4, a GLP-1 receptor agonist that can cross the blood brain barrier, was subcutaneously administered to adult mice. We then extracted the total and the plasma membrane proteins from the mouse neocortex. Exendin-4 significantly increased the phosphorylation level of cAMP response element-binding protein (CREB). Consistently, the expression level of brain-derived neurotrophic factor (BDNF), a transcriptional target of CREB, was increased. Furthermore, exendin-4 increased the membrane protein level of the AMPA receptor GluR1 subunit and postsynaptic density protein-95 (PSD-95), whereas GluR2 was unaffected. These exendin-4-dependent increases in membrane GluR1, total PSD-95 and BDNF were abrogated by pretreatment with temozolomide (TMZ), a DNA-alkylating agent, indicating that these alterations were dependent on exendin-4-induced transcriptional activity. In addition, we found that exendin-4 increased the level of the α-C terminal fragment (α-CTF) of amyloid precursor protein (APP). Furthermore, protein levels of both mature and immature ADAM10, the α-secretase of APP in the plasma membrane, were increased, whereas the total mature and immature ADAM10 levels were unchanged. These exendin-4-dependent increases in α-CTF and ADAM10 were not affected by TMZ. These findings suggested that GLP-1 facilitates the GluR1 membrane insertion through CREB activation and increases α-secretase activity through ADAM10 membrane trafficking. Upregulation of GluR1 and ADAM10 at the plasma membrane were also observed in mice with intracerebroventricular administration of Aβ oligomer, indicating that a part of benefit of exendin-4 against AD may depend on the GluR1 and ADAM10 membrane trafficking.

Differential effects of prenatal chronic high-decibel noise and music exposure on the excitatory and inhibitory synaptic components of the auditory cortex analog in developing chicks (Gallus gallus domesticus)

Proper development of the auditory cortex depends on early acoustic experience that modulates the balance between excitatory and inhibitory (E/I) circuits. In the present social and occupational environment exposure to chronic loud sound in the form of occupational or recreational noise, is becoming inevitable. This could especially disrupt the functional auditory cortex development leading to altered processing of complex sound and hearing impairment. Here we report the effects of prenatal chronic loud sound (110-dB sound pressure level (SPL)) exposure (rhythmic [music] and arrhythmic [noise] forms) on the molecular components involved in regulation of the E/I balance in the developing auditory cortex analog/Field L (AuL) in domestic chicks. Noise exposure at 110-dB SPL significantly enhanced the E/I ratio (increased expression of AMPA receptor GluR2 subunit and glutamate with decreased expression of GABA(A) receptor gamma 2 subunit and GABA), whereas loud music exposure maintained the E/I ratio. Expressions of markers of synaptogenesis, synaptic stability and plasticity i.e., synaptophysin, PSD-95 and gephyrin were reduced with noise but increased with music exposure. Thus our results showed differential effects of prenatal chronic loud noise and music exposures on the E/I balance and synaptic function and stability in the developing auditory cortex. Loud music exposure showed an overall enrichment effect whereas loud noise-induced significant alterations in E/I balance could later impact the auditory function and associated cognitive behavior.

Metabolism peritumorous zone and alteration AMPAand NMDA-glutamate receptors in the pathogenesis of gliomas of the cerebral hemispheres

Examined 12 patients with gliomas of the big hemispheres of a brain. Used immunoenzyme method for semiquantitative determination of the level of autoantibodies to NR2A-subunit of NMDA- and GluR1-subunit of AMPA-receptors of glutamate. All patients were performed positron emission tomography of the brain with 2 radiopharmaceuticals: 2-[ 18 F] fluoro-2-deoxy-D-glucose and L-[methyl- 11 C]-methionine. Features of alteration of NMDA- and AMPA-receptors of a glutamate and sequence of changes of a metabolism in a perifocal zone in gliomas of the cerebral hemispheres are studied. It is shown pre-emptive increase the level of autoantibodies to GluR1- subunit of AMPA-receptors of glutamate in patients with gliomas, current with epileptic syndrome.

Distribution of AMPA receptor subunit glur1 in the bed nucleus of the stria terminalis and effect of stress

The brain circuitry thought to be involved in stress responses includes several nuclei of the extended amygdala. The bed nucleus of the stria terminalis (BNST) is thought to be involved in the generation of sustained, nonspecific anxiety. Previous behavioral and electrophysiological experiments demonstrate that glutamate systems are involved in anxiety-like behaviors in the BNST. Antagonists for AMPA receptors injected into the BNST decrease anxiety-like behaviors. However, little is known about the role of AMPA receptors and the mechanism by which they act in the establishment of anxiety-like behavior in response to a stressor. We hypothesized that the distribution of AMPA receptors is changed following a paradigm of unpredictable footshock as has been seen in the basolateral amygdala (BLA). We examined the subcellular localization of the GluR1 subunits of the AMPA receptor. We found that the neuropil of the BNST had a lower density of dendritic spines compared to dendritic shafts in the BLA. The majority of elements immunolabeled for GluR1 were dendritic shafts and spines with axonal and glial elements rarely labeled. Compared with controls, no significant effect was observed on days 1, 6, or 14 poststress. However, there was a trend for an increase at 6 and 14 days poststress. These data demonstrate that GluR1 subunits are primarily located on postsynaptic elements in the BNST. Moreover, it was shown that the response of the AMPA GluR1 subunit does not undergo a significant migration into spines from dendrites in response to a stressor as has been demonstrated in the BLA.

Involvement of prefrontal AMPA receptors in encounter stimulation-induced hyperactivity in isolation-reared mice

We recently showed that social encounter stimulation induces hyperactivity in mice reared in social isolation from early life and this is associated with the transient activation of prefrontal dopaminergic and serotonergic systems. In the present study, we examined the effect of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptor antagonist 2, 3-dioxo-6-nitro-1, 2, 3, 4-tetrahydrobenzo[f]quinoxaline-7-sulfonamide (NBQX) on encounter-induced behavioural and neurochemical changes to study the role of the receptor in abnormal behaviours in isolation-reared mice. The encounter to an intruder mouse induced hyperactivity with transient increases in prefrontal dopamine and serotonin levels in isolation-reared mice. NBQX attenuated the encounter-induced hyperactivity and the associated neurochemical changes in isolation-reared mice. In addition, NBQX reduced aggressive behaviour and cognitive impairment in isolation-reared mice, but did not affect depressive-like behaviour or spontaneous hyper-locomotion in these animals. The AMPA receptor agonist (S)-AMPA increased prefrontal dopamine and serotonin release, and this effect was higher in isolation-reared mice than in the group-reared mice, suggesting higher prefrontal AMPA receptor activity in isolation-reared mice. Furthermore, isolation rearing increased the expression of AMPA receptor subunits (GluR1, GluR2 and GluR3) and GluR1 Ser845 phosphorylation in the prefrontal cortex, but not in the hippocampus or nucleus accumbens. Taken together, these results suggest that an increase in AMPA receptor activity in the prefrontal cortex contributes to some, but not all, abnormal behaviours in isolation-reared mice.

Epileptic syndrome in the clinical picture of the diseaseand the level of antibodies to GluR1 subunit of AMPA glutamate receptors in the patients with gliomas in the cerebral hemispheres of a brain

The authors examined 92 patients with gliomas in the cerebral hemispheres. The immunoenzyme method was used for semiquantitative assay of the level of autoantibodies to GluR1 subunit of AMPA receptors of glutamate. Frequency and clinical features of symptomatic epilepsy, the reaction of AMPA receptors of glutamate depending on localization and degree of malignance and features of clinical course of the disease wereinvestigated as well. Marked increase of the level of autoantibodies to GluR1 subunit of AMPA receptors of glutamate was noticed in the patients with gliomas associated with epileptic syndrome. Maximal level of autoantibodies to GluR1 subunit of AMPA receptors of glutamate seen under the effect of the tumor on the frontal and temporal lobels.

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.

IS 36. Molecular and cellular effects of repetitive magnetic stimulation

Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive brain stimulation technique, which can alter cortical excitability in human subjects for hours beyond the period of stimulation. Therefore, it has therapeutic potential in neurological and psychiatric disorders associated with alterations in cortical excitability. However, rTMS-induced effects remain poorly understood at the molecular and cellular level. This presentation will provide a review on recent findings from other groups on repetitive magnetic stimulation effects on immediate early gene expression (such as c-fos and zif268), protein expression (such as parvalbumin and calbindin in inhibitory interneurons), or markers of neuroplasticity (such as BDNF and GluR1 subunit of AMPA receptor). Furthermore, recent evidence from our group will be provided that repetitive magnetic stimulation can induce a long-lasting increase in glutamatergic synaptic strength, which is accompanied by structural remodeling of dendritic spines and postsynaptic NMDA-receptor-mediated accumulation of GluA1-containing AMPA-receptors. Together, there is accumulating evidence that the repetitive magnetic stimulation induces specific changes of gene and protein regulation and ultimately functional and structural synaptic plasticity at the cellular level. Repetitive magnetic stimulation in small animals, slices and cell cultures may provide useful experimental models for development and prediction of therapeutically effective rTMS protocols in humans.

N-linked glycosylation of cortical N-methyl-D-aspartate and kainate receptor subunits in schizophrenia.

Dysfunctional glutamate neurotransmission has been implicated in the pathophysiology of schizophrenia. Abnormal expressions in schizophrenia of ionotropic glutamate receptors (iGluRs) and the proteins that regulate their trafficking have been found to be region and subunit specific in brain, suggesting that abnormal trafficking of iGluRs may contribute toward altered glutamatergic neurotransmission. The post-translational modification N-glycosylation of iGluR subunits can be used as a proxy for their intracellular localization. Receptor complexes assemble in the lumen of the endoplasmic reticulum, where N-glycosylation begins with the addition of N-linked oligomannose glycans, and is subsequently trimmed and replaced by more elaborate glycans while trafficking through the Golgi apparatus. Previously, we found abnormalities in N-glycosylation of the GluR2 AMPA receptor subunit in schizophrenia. Here, we investigated N-glycosylation of N-methyl-D-aspartate and kainate (KA) receptor subunits in the dorsolateral prefrontal cortex from patients with schizophrenia and a comparison group. We used enzymatic deglycosylation with two glycosidases: endoglycosidase H (Endo H), which removes immature high mannose-containing sugars, and peptide-N-glycosidase F (PNGase F), which removes all N-linked sugars. The NR1, NR2A, NR2B, GluR6, and KA2 subunits were all sensitive to treatment with Endo H and PNGase F. The GluR6 KA receptor subunit was significantly more sensitive to Endo H-mediated deglycosylation in schizophrenia, suggesting a larger molecular mass of N-linked high mannose and/or hybrid sugars on GluR6. This finding, taken with our previous work, suggests that a cellular mechanism underlying abnormal glutamate neurotransmission in schizophrenia may involve abnormal trafficking of both AMPA and KA receptors.

Effects of electroacupuncture on spinal α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor in rats injected with complete Freund’s adjuvant

The effects of electroacupuncture (EA) on spinal α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptor subunits in male rats injected with complete Freund's adjuvant (CFA) were investigated. Bilateral EA stimulation (2 Hz, 1 mA) was administered by needle insertion for 30 min once daily at acupoints corresponding to Zusanli and Sanyinjiao, and the thermal thresholds were measured. To examine the changes in the AMPA receptor subunits, the L4-5 segments of the spinal cord were analyzed by qPCR, western blot analysis and immunohistochemistry. The CFA-induced thermal sensitivity of the rat hind paw was significantly inhibited by EA stimulation from day 3 following CFA injection. On day 5 following CFA injection, there were no significant changes in the expression of the AMPA receptor GluR1 subunit in the CFA-injected rats with or without EA stimulation, compared with the control rats. However, the expression of the GluR2 subunit was significantly decreased by CFA treatment. Western blot analysis revealed that the expression of the phosphorylated GluR1 subunit in the control rats was not significantly different compared with that in the CFA-injected rats with and without EA stimulation. However, phosphorylation of the ipsilateral GluR2 subunit was significantly increased in the CFA-injected rats, and this activation was prevented by EA stimulation. Immunohistochemical analysis revealed a greater expression of phospho-GluR2 following CFA injection, which was inhibited by EA stimulation. These results suggested that phosphorylation of the AMPA receptor, particularly the GluR2 subunit, may be important in EA analgesia of CFA-induced inflammation.

Depalmitoylation preferentially downregulates AMPA induced Ca2+ signaling and neurotoxicity in motor neurons

Excessive activation of AMPA receptor has been implicated in motor neuron degeneration in amyotrophic lateral sclerosis (ALS). However, it is not clear why motor neurons are preferentially sensitive to AMPA receptor mediated excessive [Ca2+]i rise and excitotoxicity. In the present study we examined whether palmitoylation regulates Ca2+ permeability of AMPA receptor and excitotoxicity in cultured spinal cord neurons. We adapted chronic 2-bromopalmitate (2-BrP) treatment to achieve depalmitoylation and examined its effect on the cytotoxicity in spinal cord neurons exposed to AMPA. The change in AMPA induced signaling and cytotoxicity in motor neurons and other spinal neurons under identical conditions of exposure to AMPA was studied. 2-BrP treatment inhibited AMPA induced rise in [Ca2+]i and cytotoxicity in both types of neurons but the degree of inhibition was significantly higher in motor neurons as compared to other spinal neurons. The AMPA induced [Na+]i rise was moderately affected in both type of neurons on depalmitoylation. Depalmitoylation reduced the expression levels of AMPA receptor subunits (GluR1 and GluR2) and also PSD-95 but stargazin levels remained unaffected. Our results demonstrate that 2-BrP attenuates AMPA receptor activated Ca2+ signaling and cytotoxicity preferentially in motor neurons and suggest that AMPA receptor modulation by depalmitoylation could play a significant role in preventing motor neuron degeneration.