Oscillatory Synchronous Inhibition in the Basolateral Amygdala and its Primary Dependence on NR2A-containing NMDA Receptors.

Synchronous, rhythmic firing of GABAergic interneurons is a fundamental mechanism underlying the generation of brain oscillations, and evidence suggests that NMDA receptors (NMDARs) play a key role in oscillatory activity by regulating the activity of interneurons. Consistent with this, derangement of brain rhythms in certain neuropsychiatric disorders, notably schizophrenia and autism, is associated with NMDAR hypofunction and loss of inhibitory interneurons. In the basolateral amygdala (BLA)-dysfunction of which is involved in a host of neuropsychiatric diseases-, principal neurons display spontaneous, rhythmic "bursts" of inhibitory activity, which could potentially be involved in the orchestration of oscillations in the BLA network; here, we investigated the role of NMDARs in these inhibitory oscillations. Rhythmic bursts of spontaneous IPSCs (0.5 Hz average burst frequency) recorded from rat BLA principal cells were blocked or significantly suppressed by D-AP5, and could be driven by NMDAR activation alone. BLA interneurons generated spontaneous bursts of suprathreshold EPSCs at a similar frequency, which were also blocked or reduced by D-AP5. PEAQX (GluN2A-NMDAR antagonist; 0.4 µM) or Ro-25-6981 (GluN2B-NMDAR antagonist; 5 µM) suppressed the IPSC and EPSC bursts; suppression by PEAQX was significantly greater than that by Ro-25-6981. Immunohistochemical labeling revealed the presence of both GluN2A- and GluN2B-NMDARs on GABAergic BLA interneurons, while, functionally, GluN2A-NMDARs have the dominant role, as suggested by a greater reduction of NMDA-evoked currents by PEAQX versus Ro-25-6981. Entrainment of BLA principal neurons in an oscillatory generation of inhibitory activity depends primarily on activation of GluN2A-NMDARs, and interneuronal GluN2A-NMDARs may play a significant role.

Association between GRIN2A promoter polymorphism and recovery from concussion.

OBJECTIVE: To determine genetic variability within the N-methyl-D-aspartate receptor 2A sub-unit (GRIN2A) gene promoter and its association with concussion recovery time. The hypothesis tested was that there would be a difference in allele and/or genotype distribution between two groups of athletes with normal and prolonged recovery. METHODS: DNA was extracted from saliva collected from a total of 87 athletes with a physician-diagnosed concussion. The (GT) variable number tandem repeats (VNTR) within the promoter region of GRIN2A was genotyped. The long (L) allele was an allele with ≥25 repeats and the short (S) allele was an allele with <25 repeats in the GT tract. Participants' recovery time was followed prospectively and was categorized as normal (≤60 days) or prolonged (>60 days). RESULTS: LL carriers were 6-times more likely to recover longer than 60 days following the concussive event (p = 0.0433) when compared to SS carriers. Additionally, L allele carriers were found more frequently in the prolonged recovery group (p = 0.048). CONCLUSION: Determining genetic influence on concussion recovery will aid in future development of genetic counselling. The clinical relevance of genotyping athletes could improve management of athletes who experience concussion injuries.

Altered NMDA receptor subunit gene expression in brains of mice showing high vs. low sensitization to ethanol.

Repeated administration of ethanol (EtOH) in mice leads to behavioural sensitization, a progressive increase in locomotor activity. Since not all mice sensitize equally to EtOH, the objective of the present study was to determine whether variability in this response is associated with altered subunit gene expression of the N-methyl-d-aspartate receptor (NMDAR), a primary target of EtOH. We examined NR1, NR2A, and NR2B expression throughout the brain during the development phase of EtOH sensitization, as well as after a 14 day withdrawal period. Male DBA/2J mice received 5-6 injections of EtOH (2.2g/kg, i.p.) or saline (SAL) and were categorized as high- (HS) or low-sensitized (LS) on the basis of locomotor activity scores after the final injection. NMDAR subunits were analyzed by in situ hybridization in brains removed either immediately following the final EtOH injection or 14 days thereafter. At the end of development phase, LS mice showed increased NR2A expression in several brain areas compared to saline controls. LS animals also had greater NR1 expression in the nucleus accumbens core (+11%, p=0.05) and shell (+14%, p=0.04) compared to HS mice, and increased NR2B expression in hippocampal CA1 (+20%, p=0.05) relative to saline-treated animals. High-sensitized mice showed increased NR2A expression in the bed nucleus of the stria terminalis when compared to controls (+54%, p=0.02). No differences in gene expression between the treatment groups were seen 14 days after the final injection. These findings suggest that region-specific NMDAR subunits may play an important role in the variability associated with the induction of EtOH sensitization. Low-sensitized mice may be more sensitive to the NMDAR inhibitory effects of EtOH, with the NR1 and NR2A subunits potentially playing a key role in the failure to sensitize upon repeated EtOH exposure.

Expression of NMDA receptor subunit 2A in the spinal cord of morphine tolerant rats / 中华行为医学与脑科学杂志

ObjectiveTo study the distribution and expression of NMDA receptor subunit 2A in the spinal cord of morphine tolerant rats. MethodsTwelve Sprague-Dawley rats were randomly divided into two groups with 6 rats each: control group (C) were intrathecally administrated 0.9% NaCl 10μl and morphine group(M) received 10μg morphine (i.t.). Drugs were administrated twice daily for 7 consecutive days. Tail flick latency (TFL) in the hot water immersion test was used to evaluate changes of thermal hyperalgesia latency of each group before and 30min after administration every morning. Rats were killed the day after last administration and L4～5 segment of the spinal cord was removed for determination the expression of NR2A by immunofluorescence method. ResultsTFL of group M was decreased gradually after chronic administration of morphine intrathecally. There was no significant difference between group M[(3.25±0.93)s] and group C[(2.66±0.27)s] on the 7th day (P＞0.05). A morphine tolerant model was established successfully. NR2A was distributed throughout the rat spinal cord. The expression of NR2A in group M(OD:9617±1233) was increased compared with group C(OD:2.66±0.93) (t=3.133,P＜0.05).ConclusionThe expression of NR2A was upregulated after repeated administration of morphine intrathecally in the superficial dorsal horn of spinal cord of morphine tolerant rats,which may be part of the mechanisms of morphine tolerance.

INFLUENCE OF PARTIALLY C-TERMINAL DELETION OF NR2A SUBUNITS ON THE SURFACE EXPRESSION AND FUNCTION OF NMDA RECEPTOR CHANNELS / 解剖学报

Objective To investigate whether the partially C-terminal deletion of NR2A subunit alters the surface expression and channel function of NMDA receptors in both HEK293 cells and cultured hippocampal neurons of rats. Methods Four plasmids for NR2A mutants with N-terminally GFP-tagged and C-terminal deletion NR2A?C1(?897L-1017S),NR2A?C2(?1024D-1142P),NR2A?C3(?1149D-1347G),and NR2A?C4(?1354S-1464V) were generated,and transfected into HEK293 cells and hippocampal neurons in culture.Surface staining was performed using anti-GFP antibody and Cy3 conjugated secondary antibody.Glutamate evoked currents were also detected using whole-cell recording. Results Positive surface staining was found for all the HEK293 cell co-transfected NR1-1a/NR2A?C1,NR1-1a/NR2A?C2,NR1-1a/NR2A?C3 or NR1-1a/NR2A?C4,and quantitative analysis showed no significant decrease in surface expression level when compared to that from NR1-1a/NR2A transfection.Glutamate-evoked currents were recorded in HEK293 cells co-transfected with NR1-1a/NR2A?C2 or NR1-1a/NR2A?C4.Surface expression level of NMDA receptor clusters on dendrites was significantly decreased in the neurons transfected with NR2A?C1,NR2A?C2 or NR2A?C3 than in those transfected with NR2A.Conclusion C-terminal deletion of NR2A subunit differentially effects surface expression of NMDA receptors in HEK293 cells and in hippocampal neurons in culture.