N-methyl-D-aspartate receptor subunit 1 regulates neurogenesis in the hippocampal dentate gyrus of schizophrenia-like mice

N-methyl-D-aspartate receptor hypofunction is the basis of pathophysiology in schizophrenia. Blocking the N-methyl-D-aspartate receptor impairs learning and memory abilities and induces pathological changes in the brain. Previous studies have paid little attention to the role of the N-methyl-D-aspartate receptor subunit 1 (NR1) in neurogenesis in the hippocampus of schizophrenia. A mouse model of schizophrenia was established by intraperitoneal injection of 0.6 mg/kg MK-801, once a day, for 14 days. In N-methyl-D-aspartate-treated mice, N-methyl-D-aspartate was administered by intracerebroventricular injection in schizophrenia mice on day 15. The number of NR1-, Ki67- or BrdU-immunoreactive cells in the dentate gyrus was measured by immunofluorescence staining. Our data showed the number of NR1-immunoreactive cells increased along with the decreasing numbers of BrdU- and Ki67-immunoreactive cells in the schizophrenia groups compared with the control group. N-methyl-D-aspartate could reverse the above changes. These results indicated that NR1 can regulate neurogenesis in the hippocampal dentate gyrus of schizophrenia mice, supporting NR1 as a promising therapeutic target in the treatment of schizophrenia. This study was approved by the Experimental Animal Ethics Committee of the Ningxia Medical University, China (approval No. 2014-014) on March 6, 2014.

Dose-dependent effects of NMDA on retinal and optic nerve morphology in rats

AIM: To investigate dose-dependent effects of N-methylD-aspartate(NMDA) on retinal and optic nerve morphology in rats.METHODS: Sprague Dawley rats, 180-250 g in weight were divided into four groups. Groups 1, 2, 3 and 4 were intravitreally administered with vehicle and NMDA at the doses 80, 160 and 320 nmol respectively. Seven days after injection, rats were euthanized, and their eyes were taken for optic nerve toluidine blue and retinal hematoxylin and eosin stainings. The TUNEL assay was done for detecting apoptotic cells.RESULTS: All groups treated with NMDA showed significantly reduced ganglion cell layer(GCL) thickness within inner retina, as compared to control group. Group NMDA 160 nmol showed a significantly greater GCL thickness than the group NMDA 320 nmol. Administration of NMDA also resulted in a dose-dependent decrease in the number of nuclei both per 100 μm GCL length and per 100 μm2 of GCL. Intravitreal NMDA injection caused dosedependent damage to the optic nerve. The degeneration of nerve fibres with increased clearing of cytoplasm was observed more prominently as the NMDA dose increased. In accordance with the results of retinal morphometry analysis and optic nerve grading, TUNEL staining demonstrated NMDA-induced excitotoxic retinal injury in a dose-dependent manner.CONCLUSION: Our results demonstrate dose-dependent effects of NMDA on retinal and optic nerve morphology in rats that may be attributed to differences in the severity of excitotoxicity and oxidative stress. Our results also suggest that care should be taken while making dose selections experimentally so that the choice might best uphold study objectives.

Ion Channel Dysregulation Following Intracerebral Hemorrhage

Injury to the brain after intracerebral hemorrhage(ICH)results from numerous complex cellular mechanisms.At present,effective therapy for ICH is limited and a better understanding of the mechanisms of brain injury is necessary to improve prognosis.There is increasing evidence that ion channel dysregulation occurs at multiple stages in primary and secondary brain injury following ICH.Ion channels such as TWIK-related K+channel 1,sulfonylurea 1 transient receptor potential melastatin 4 and glutamate-gated channels affect ion homeostasis in ICH.They in turn participate in the formation of brain edema,disruption of the blood-brain barrier,and the generation of neurotoxicity.In this review,we summarize the interaction between ions and ion channels,the effects of ion channel dysregulation,and we discuss some therapeutics based on ion-channel modulation following ICH.

Steroid Receptor Coactivator 3 Regulates Synaptic Plasticity and Hippocampus-dependent Memory

Steroid hormones play important roles in brain development and function.The signaling of steroid hormones depends on the interaction between steroid receptors and their coactivators.Although the function of steroid receptor coactivators has been extensively studied in other tissues,their functions in the central nervous system are less well investigated.In this study,we addressed the function of steroid receptor coactivator 3(SRC3)–a member of the p160 SRC protein family that is expressed predominantly in the hippocampus.While hippocampal development was not altered in Src3^(+/-) mice,hippocampus-dependent functions such as short-term memory and spatial memory were impaired.We further demonstrated that the deficient learning and memory in Src3^(+/-) mice was strongly associated with the impairment of long-term potentiation(LTP)at Schaffer Collateral-CA1 synapses.Mechanistic studies indicated that Src3^(+/-) mutation altered the composition of N-methyl-D-aspartate receptor subunits in the postsynaptic densities of hippocampal neurons.Finally,we showed that SRC3 regulated synaptic plasticity and learning mainly dependent on its lysine acetyltransferase activity.Taken together,these results reveal previously unknown functions of SRC3 in the hippocampus and thus may provide insight into how steroid hormones regulate brain function.