Effects of neonatal MK-801 exposure on recognition memory and excitatory-inhibitory balance of hippocampus in adult female rats / 中华行为医学与脑科学杂志

Objective To investigate the long-term effects of repeated neonatal administration of dizocipline maleate (MK-801),the glutamate N-methyl-D-aspartate (NMDA) receptor antagonist,on recognition memory and hippocampal excitatory-inhibitory balance at the synaptic level in adult female rats.Methods Neonatal female Sprague-Dawley (SD) rats were randomly divided into model group and control group.Rats were administrated subcutaneously with MK-801 or normal saline from postnatal day (PND) 5 to PND14 (0.25 mg/kg,twice daily).(1) Object-in-context recognition test was performed on PND73-75.(2)The expression levels of vesicular glutamate transporter 1 (VGLUT1) and vesicular GABA transporter (VGAT) in hippocampus were detected by immunohistochemical staining.Results (1) The preference index of model group for new objects was significantly lower than that of the control group (t =-2.762,P=0.012).(2) There was no significant difference in the expression of VGLUT1 in hippocampus of MK-801 mode group(P＞0.05).Compared with control group(48.19±2.10),the VGAT level of model group in CA1 (39.60±2.19) was lower.Compared with control group (CA1:(0.99±0.05),CA3:(1.28±0.02),the ratio of VGLUT1/VGAT was significantly upregulated in CA1(1.16±0.05) and CA3(1.44±0.03) (P＜0.05).Conclusion Early NMDA receptor inhibition produces long-term deleterious effects on associative recognition memory and excitatory-inhibitory balance of hippocampus in female rats.These biochemical abnormalities may contribute to cognitive impairments observed in this study.

Sex Differences in Autism-Like Behavioral Phenotypes and Postsynaptic Receptors Expression in the Prefrontal Cortex of TERT Transgenic Mice

Autism spectrum disorder (ASD) remains unexplained and untreated despite the high attention of research in recent years. Aside from its various characteristics is the baffling male preponderance over the female population. Using a validated animal model of ASD which is the telomerase reverse transcriptase overexpressing mice (TERT-tg), we conducted ASD-related behavioral assessments and protein expression experiments to mark the difference between male and females of this animal model. After statistically analyzing the results, we found significant effects of TERT overexpression in sociability, social novelty preference, anxiety, nest building, and electroseizure threshold in the males but not their female littermates. Along these differences are the male-specific increased expressions of postsynaptic proteins which are the NMDA and AMPA receptors in the prefrontal cortex. The vGluT1 presynaptic proteins, but not GAD, were upregulated in both sexes of TERT-tg mice, although it is more significantly pronounced in the male group. Here, we confirmed that the behavioral effect of TERT overexpression in mice was male-specific, suggesting that the aberration of this gene and its downstream pathways preferentially affect the functional development of the male brain, consistent with the male preponderance in ASD.

Sex Differences in Autism-Like Behavioral Phenotypes and Postsynaptic Receptors Expression in the Prefrontal Cortex of TERT Transgenic Mice

Autism spectrum disorder (ASD) remains unexplained and untreated despite the high attention of research in recent years. Aside from its various characteristics is the baffling male preponderance over the female population. Using a validated animal model of ASD which is the telomerase reverse transcriptase overexpressing mice (TERT-tg), we conducted ASD-related behavioral assessments and protein expression experiments to mark the difference between male and females of this animal model. After statistically analyzing the results, we found significant effects of TERT overexpression in sociability, social novelty preference, anxiety, nest building, and electroseizure threshold in the males but not their female littermates. Along these differences are the male-specific increased expressions of postsynaptic proteins which are the NMDA and AMPA receptors in the prefrontal cortex. The vGluT1 presynaptic proteins, but not GAD, were upregulated in both sexes of TERT-tg mice, although it is more significantly pronounced in the male group. Here, we confirmed that the behavioral effect of TERT overexpression in mice was male-specific, suggesting that the aberration of this gene and its downstream pathways preferentially affect the functional development of the male brain, consistent with the male preponderance in ASD.

Valproic Acid Induces Telomerase Reverse Transcriptase Expression during Cortical Development

The valproic acid (VPA)-induced animal model is one of the most widely utilized environmental risk factor models of autism. Autism spectrum disorder (ASD) remains an insurmountable challenge among neurodevelopmental disorders due to its heterogeneity, unresolved pathological pathways and lack of treatment. We previously reported that VPA-exposed rats and cultured rat primary neurons have increased Pax6 expression during post-midterm embryonic development which led to the sequential upregulation of glutamatergic neuronal markers. In this study, we provide experimental evidence that telomerase reverse transcriptase (TERT), a protein component of ribonucleoproteins complex of telomerase, is involved in the abnormal components caused by VPA in addition to Pax6 and its downstream signals. In embryonic rat brains and cultured rat primary neural progenitor cells (NPCs), VPA induced the increased expression of TERT as revealed by Western blot, RT-PCR, and immunostainings. The HDAC inhibitor property of VPA is responsible for the TERT upregulation. Chromatin immunoprecipitation revealed that VPA increased the histone acetylation but blocked the HDAC1 binding to both Pax6 and Tert genes. Interestingly, the VPA-induced TERT overexpression resulted to sequential upregulations of glutamatergic markers such as Ngn2 and NeuroD1, and inter-synaptic markers such as PSD-95, α-CaMKII, vGluT1 and synaptophysin. Transfection of Tert siRNA reversed the effects of VPA in cultured NPCs confirming the direct involvement of TERT in the expression of those markers. This study suggests the involvement of TERT in the VPA-induced autistic phenotypes and has important implications for the role of TERT as a modulator of balanced neuronal development and transmission in the brain.