Functional human GRIN2B promoter polymorphism and variation of mental processing speed in older adults

Cyclooxygenase-2 inhibition affects the ratio of GluN2A/GluN2B receptor subunits through interaction with mGluR5 in the mouse brain

N-methyl-D-aspartic acid receptors (NMDARs) are the most studied receptors in mammalian brains. Their role in depression, cognition, schizophrenia, learning and memorization, Alzheimer's disease, and more is well documented. In the search for new drug candidates in depression, intensive studies have been conducted. Compounds that act by influencing NMDARs have been particularly intensively investigated following the success of ketamine in clinics. Unfortunately, the side effects associated with ketamine do not allow it to be useful in all cases. Therefore, it is important to learn about new unknown mechanisms related to NMDAR activation and study the impact of changes in the excitatory synapse environment on this receptor. Both direct and intermediary influence on NMDARs via mGluRs and COX-2 are effective. Our prior studies showed that both mGluRs ligands and COX-2 inhibitors are potent in depression-like and cognitive studies through mutual interactions. The side effects associated with imipramine administration, e.g., memory impairment, were improved when inhibiting COX-2. Therefore, this study is a trial that involves searching for modifications in NMDARs in mouse brains after prolonged treatment with MTEP (mGluR5 antagonist), NS398 (COX-2 inhibitor), or imipramine (tricyclic antidepressant). The prefrontal cortex (PFC) and hippocampus (HC) were selected for PCR and Western blot analyses. Altered expression of Gin2a or Grin2b genes after treatment was found. The observed effects were more potent when COX-2 was inhibited. The finding described here may be vital when searching for new drugs acting via NMDARs without the side effects related to cognition.

Potential cross-species correlations in social hierarchy and memory between mice and young children

Social hierarchy is associated with various phenotypes. Although memory is known to be important for hierarchy formation, the difference in memory abilities between dominant and subordinate individuals remains unclear. In this study, we examined memory performance in mice with different social ranks and found better memory abilities in dominant mice, along with greater long-term potentiation and higher memory-related gene expression in the hippocampus. Daily injection of memory-improving drugs could also enhance dominance. To validate this correlation across species, through inventory, behavioral and event-related potential studies, we identified better memory abilities in preschool children with higher social dominance. Better memory potentially helped children process dominance facial cues and learn social strategies to acquire higher positions. Our study shows a remarkable similarity between humans and mice in the association between memory and social hierarchy and provides valuable insight into social interactions in young animals, with potential implications for preschool education.

Memory performance and hippocampal memory-related gene expression are shown to both be increased in more dominant mice, with memory-improving drugs enhancing dominant behaviour. The data also suggests that children with better memory can recognise dominance more easily, demonstrating a potential cross-species correlation in the association between memory and social hierarchy.

Evidence for the Association between the Intronic Haplotypes of Ionotropic Glutamate Receptors and First-Episode Schizophrenia

The heritable component of schizophrenia (SCH) as a polygenic trait is represented by numerous variants from a heterogeneous group of genes each contributing a relatively small effect. Various SNPs have already been found and analyzed in genes encoding the NMDAR subunits. However, less is known about genetic variations of genes encoding the AMPA and kainate receptor subunits. We analyzed sixteen iGluR genes in full length to determine the sequence variability of iGluR genes. Our aim was to describe the rate of genetic variability, its distribution, and the co-occurrence of variants and to identify new candidate risk variants or haplotypes. The cumulative effect of genetic risk was then estimated using a simple scoring model. GRIN2A-B, GRIN3A-B, and GRIK4 genes showed significantly increased genetic variation in SCH patients. The fixation index statistic revealed eight intronic haplotypes and an additional four intronic SNPs within the sequences of iGluR genes associated with SCH (p < 0.05). The haplotypes were used in the proposed simple scoring model and moreover as a test for genetic predisposition to schizophrenia. The positive likelihood ratio for the scoring model test reached 7.11. We also observed 41 protein-altering variants (38 missense variants, four frameshifts, and one nonsense variant) that were not significantly associated with SCH. Our data suggest that some intronic regulatory regions of iGluR genes and their common variability are among the components from which the genetic predisposition to SCH is composed.

Positive allosteric modulation of NMDA receptors: mechanisms, physiological impact and therapeutic potential

NMDA receptors (NMDARs) are glutamate-gated ion channels that play key roles in synaptic transmission and plasticity. Both hyper- and hypo-activation of NMDARs are deleterious to neuronal function. In particular, NMDAR hypofunction is involved in a wide range of neurological and psychiatric conditions like schizophrenia, intellectual disability, age-dependent cognitive decline, or Alzheimer's disease. While early medicinal chemistry efforts were mostly focused on the development of NMDAR antagonists, the last 10 years have seen a boom in the development of NMDAR positive allosteric modulators (PAMs). Here we review the currently developed NMDAR PAMs, their pharmacological profiles and mechanisms of action, as well as their physiological effects in healthy animals and animal models of NMDAR hypofunction. In light of the complexity of physiological outcomes of NMDAR PAMs in vivo, we discuss the remaining challenges and questions that need to be addressed to better grasp and predict the therapeutic potential of NMDAR positive allosteric modulation.

ETS-domain containing protein (Elk1) suppression protects cortical neurons against oxygen-glucose deprivation injury

ETS-domain containing protein (Elk1), which is a transcription factor, is reported to be closely related to the apoptosis of primary neurons and could be activated by hypoxia in human microvascular endothelial cells. In this study, we aimed to investigate the role of Elk1 in cortical neurons under oxygen-glucose deprivation (OGD) conditions. The OGD model of cortical neurons was established the anoxia/hypoglycemia-induced injury and the in vivo model was established by middle cerebral artery occlusion (MCAO). Elk1 mRNA and protein expression was significantly up-regulated in neurons exposed to OGD for 24 h, and mRNA expression was also markedly increased in cerebral cortex of rats with MCAO after 10 days. The knockdown of Elk1 in neurons without OGD obviously constrained Fra-1 and promoted Nrf2 expression. Also, Elk1 inhibition suppressed neuronal apoptosis, caspase-3 activity, LDH leakage, and MDA and SOD contents, while it increased cell viability in the neurons with OGD. The overexpression of Fra-1 showed a reverse effect on caspase-3 activity, cell viability and SOD contents in neurons under OGD conditions compared with Elk1 knockdown. Thus, Elk1 inhibition has a protective effect on neurons against OGD-induced injury.