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Evidence suggests that transient receptor potential (TRP) ion channels dysfunction significantly contributes to the physiopathology of metabolic and neurological disorders. Dysregulation in functions and expression in genes encoding the TRP channels cause several inherited diseases in humans (the so-called 'TRP channelopathies'), which affect the cardiovascular, renal, skeletal, and nervous systems. This study aimed to evaluate the expression of ion channels in the forebrain of rats with diet-induced obesity (DIO). DIO rats were studied after 17 weeks under a hypercaloric diet (high-fat diet, HFD) and were compared to the control rats with a standard diet (CHOW). To determine the systemic effects of HFD exposure, we examined food intake, fat mass content, fasting glycemia, insulin levels, cholesterol, and triglycerides. qRT-PCR, Western blot, and immunochemistry analysis were performed in the frontal cortex (FC) and hippocampus (HIP). After 17 weeks of HFD, DIO rats increased their body weight significantly compared to the CHOW rats. In DIO rats, TRPC1 and TRPC6 were upregulated in the HIP, while they were downregulated in the FC. In the case of TRPM2 expression, instead was increased both in the HIP and in the FC. These could be related to the increase of proteins and nucleic acid oxidation. TRPV1 and TRPV2 gene expression showed no differences both in the FC and HIP. In general, qRT-PCR analyses were confirmed by Western blot analysis. Immunohistochemical procedures highlighted the expression of the channels in the cell body of neurons and axons, particularly for the TRPC1 and TRPC6. The alterations of TRP channel expression could be related to the activation of glial cells or the neurodegenerative process presented in the brain of the DIO rat highlighted with post synaptic protein (PSD 95) alterations. The availability of suitable animal models may be useful for studying possible pharmacological treatments to counter obesity-induced brain injury. The identified changes in DIO rats may represent the first insight to characterize the neuronal alterations occurring in obesity. Further investigations are necessary to characterize the role of TRP channels in the regulation of synaptic plasticity and obesity-related cognitive decline.

Background: FMRP is a selective mRNA-binding protein that regulates protein synthesis at synapses, and its loss may lead to the impairment of trace fear memory. Previously, we found that FMRP levels in the hippocampus of rats with post-traumatic stress disorder (PTSD) were decreased. However, the mechanism underlying these changes remains unclear., Methods: Forty-eight male Sprague-Dawley rats were randomly divided into four groups. The experimental groups were treated with the single-prolonged stress (SPS) procedure and injected with a lentivirus-mediated inhibitor of miR-142-5p. Behavior test as well as morphology and molecular biology experiments were performed to detect the effect of miR-142 downregulation on PTSD, which was further verified by in vitro experiments., Results: We found that silence of miRNA-142 (miR-142), an upstream regulator of FMRP, could alleviate PTSD-like behaviors of rats exposed to the SPS paradigm. MiR-142 silence not only decreased the levels of proinflammatory mediators, such as interleukin-1β, interleukin-6, and tumor necrosis factor-α, but also increased the expressive levels of synaptic proteins including PSD95 and synapsin I in the hippocampus, which was one of the key brain regions associated with PTSD. We further detected that miR-142 silence also downregulated the transportation of nuclear factor kappa-B (NF-κB) into the nuclei of neurons and might further affect the morphology of neurons., Conclusions: The results revealed miR-142 downregulation could alleviate PTSD-like behaviors through attenuating neuroinflammation in the hippocampus of SPS rats by binding to FMRP.

Background: Aberrant hippocampal neurogenesis is an important pathological feature of sepsis-associated encephalopathy. In the current study, we examined the potential role of the long noncoding RNA (lncRNA) sex-determining region Y-box 2 (SOX2) overlapping transcript (SOX2OT), a known regulator of adult neurogenesis in sepsis-induced deficits in hippocampal neurogenesis and cognitive function., Methods: Sepsis was induced in adult C57BL/6 J male mice by cecal ligation and perforation (CLP) surgery. Randomly selected CLP mice were transfected with short interfering RNAs (siRNAs) against SOX2OT or SOX2, or with scrambled control siRNA. Cognitive behavior was tested 8-12 days post-surgery using a Morris water maze. Western blotting and RT-qPCR were used to determine expression of SOX2, Ki67, doublecortin (DCX), nestin, brain lipid-binding protein, and glial fibrillary acidic protein (GFAP) in the hippocampus. The number of bromodeoxyuridine (BrdU) + /DCX + cells, BrdU + /neuronal nuclei (NeuN) + neurons, and BrdU + /GFAP + glial cells in the dentate gyrus were assessed by immunofluorescence., Results: CLP mice showed progressive increases in SOX2OT and SOX2 mRNA levels on days 3, 7, and 14 after CLP surgery, accompanied by impaired cognitive function. Sepsis led to decrease in all neuronal markers in the hippocampus, except GFAP. Immunofluorescence confirmed the decreased numbers of BrdU + /DCX + cells and BrdU + /NeuN + neurons, and increased numbers of BrdU + /GFAP + cells. SOX2OT knockdown partially inhibited the effects of CLP on levels of SOX2 and neuronal markers, neuronal populations in the hippocampus, and cognitive function. SOX2 deficiency recapitulated the effects of SOX2OT knockdown., Conclusion: SOX2OT knockdown improves sepsis-induced deficits in hippocampal neurogenesis and cognitive function by downregulating SOX2 in mice. Inhibiting SOX2OT/SOX2 signaling may be effective for treating or preventing neurodegeneration in sepsis-associated encephalopathy.

Changes in the expression of HCN ion channels leading to changes in I h function and neuronal excitability are considered to be possible mechanisms involved in epileptogenesis in kinds of human epilepsy. In previous animal studies of febrile seizures and temporal lobe epilepsy, changes in the expression of HCN1 and HCN2 channels at different time points and in different parts of the brain were not consistent, suggesting that transcriptional disorders involving HCNs play a crucial role in the epileptogenic process. Therefore, we aimed to assess the transcriptional regulation of HCN channels in Medial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS) patients. This study included eight nonhippocampal sclerosis patients and 40 MTLE-HS patients. The mRNA expression of HCN channels was evaluated by qRT-PCR, while the protein expression was quantitatively analyzed by Western blotting. The subcellular localization of HCN channels in the hippocampus was explored by immunofluorescence. We demonstrated that the mRNA and protein expression of HCN1 and HCN2 are downregulated in controls compared to that in MTLE-HS patients. In the hippocampal CA1/CA4 subregion and GCL, in addition to a large decrease in neurons, the expression of HCN1 and HCN2 on neuronal cell membranes was also downregulated in MTLE-HS patients. These findings suggest that the expression of HCN channels are downregulated in MTLE-HS, which indicates that the decline in HCN channels in the hippocampus during chronic epilepsy in MTLE-HS patients leads to the downregulation of I h current density and function, thereby reducing the inhibitory effect and increasing neuronal excitability and eventually causing disturbances in the electrical activity of neurons., (© 2020 Wiley Periodicals, Inc.)

This study investigated the effect of a high-fat diet rich in corn oil (CO-HFD) on the memory retention and hippocampal oxidative stress, inflammation, and apoptosis in rats, and examined if the underlying mechanisms involve modulating Resolvin D1 (RvD1) levels and activation of p 66 Shc. Also, we tested if co-administration of RvD1 could prevent these neural adverse effects induced by CO-HFD. Adult male Wistar rats were divided into 4 groups (n = 18/each) as control fed standard diet (STD) (3.82 kcal/g), STD + RvD1 (0.2 µg/Kg, i.p/twice/week), CO-HFD (5.4 kcal/g), and CO-HFD + RvD1. All treatments were conducted for 8 weeks. With normal fasting glucose levels, CO-HFD induced hyperlipidemia, hyperinsulinemia, increased HOMA-IRI and reduced the rats' memory retention. In parallel, CO-HFD increased levels of reactive oxygen species (ROS), malondialdehyde (MDA), cytoplasmic cytochrome-c, and cleaved caspase-3 and significantly decreased levels of glutathione (GSH), Bcl-2, and manganese superoxide dismutase (MnSOD) in rats' hippocampi. Besides, CO-HFD significantly reduced hippocampal levels of docosahexaenoic acid (DHA) and RvD1, as well as total protein levels of Nrf2 and significantly increased nuclear protein levels of p-NF-κB. Concomitantly, CO-HFD increased hippocampal protein levels of p-JNK, p53, p 66 Shc, p-p 66 Shc, and NADPH oxidase. However, without altering plasma and serum levels of glucose, insulin, and lipids, co-administration of RvD1 to CO-HFD completely reversed all these events. It also resulted in similar effects in the STD fed-rats. In conclusion, CO-HFD impairs memory function and induces hippocampal damage by reducing levels of RvD1 and activation of JNK/p53/p 66 Shc/NADPH oxidase, effects that are prevented by co-administration of RvD1.

Epilepsy is a common neurological disorder characterised by occurrence of spontaneous recurrent epileptiform discharges (SREDs) in neurons. The cellular mechanisms that underlie epilepsy are known to be regulated by brain-derived neurotrophic factor. However, some studies show that tropomyosin-related kinase B (TrkB), which is the receptor for BDNF, plays an important role in the pathophysiology of epilepsy. Our previous research revealed that truncated TrkB receptors are upregulated in a rat hippocampal neuronal model of SREDs. In contrast, full-length TrkB receptors are downregulated. Furthermore, the activation of full-length TrkB signaling is suppressed by the overexpression of truncated TrkB. In this study, to regulate the expression of truncated TrkB receptor and full-length TrkB signaling, rno-miR-185-3p was transduced into the SREDs model. Then, the changes in the activity of L-type voltage-gated calcium channels (VGCCs) and in epileptiform discharges were investigated. Transduction of rno-miR-185-3p downregulated the expression of truncated TrkB and dramatically activated full-length TrkB signaling in the model. Next, we found that the activation of full-length TrkB signaling decreased the maximal Ca 2+ current density in the model, delayed the steady-state activation and accelerated the inactivation of L-type VGCCs. Finally, the epileptiform discharges in the model could be impaired. Based on the above results, we suggest that the activation of full-length TrkB signaling may suppress the properties of L-type VGCCs, and thus ameliorate the epileptiform discharges in the model. The activation of full-length TrkB signaling may affect the inhibition of epilepsy. This provides a rationale for the activation of full-length TrkB signaling in preventive therapies.

Ischemic stroke is a major cause of death and motor disabilities all over the world. It is a muti-factorial disorder associated with inflammatory, apoptotic, and oxidative responses. Nateglinide (NAT), an insulinotropic agent used for the treatment of type 2 diabetes mellitus, recently showed potential anti-inflammatory and anti-apoptotic effects. The aim of our study was to elucidate the unique neuroprotective role of NAT in the middle cerebral artery occlusion (MCAO)-induced stroke in rats. Fifty-six male rats were divided to 4 groups (n = 14 in each group): the sham-operated group, sham receiving NAT (50 mg/kg/day, p.o) group, ischemia/reperfusion (IR) group, and IR receiving NAT group (50 mg/kg/day, p.o). MCAO caused potent deficits in motor and behavioral functions of the rats. Significant increase in inflammatory and apoptotic biomarkers has been observed in rats' hippocampi. Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) pathway was significantly stimulated causing activation of series inflammatory biomarkers ending up neuro-inflammatory milieu. Pretreatment with NAT preserved rats' normal behavioral and motor functions. Moreover, NAT opposed the expression of hypoxia-inducible factor-1α (HIF-1α) resulting in downregulation of more inflammatory mediators namely, NF-κB, tumor necrosis factor-β (TNF-β), and the anti-survival gene PMAIP-1. NAT stimulated caveolin-1 (Cav-1) which prevented expression of oxidative biomarkers, nitric oxide (NO), and myeloperoxidase (MPO) and hamper the activation of apoptotic biomarker caspase-3. In conclusion, our work postulated that NAT exhibited its neuroprotective effects in rats with ischemic stroke via attenuation of different unique oxidative, apoptotic, and inflammatory pathways.

The hyperpolarization-activated cyclic-nucleotide-gated non-selective cation (HCN) channels play a potential role in the neurological basis underlying drug addiction. However, little is known about the role of HCN channels in methamphetamine (METH) abuse. In the present study, we examined the changes in working memory functions of METH re-exposed mice through Morris water maze test, and investigated the protein expression of HCN1 channels and potential mechanisms underlying the modulation of HCN channels by Western blotting analysis. Mice were injected with METH (1 mg/kg, i.p.) once per day for 6 consecutive days. After 5 days without METH, mice were re-exposed to METH at the same concentration. We found that METH re-exposure caused an enhancement of working memory, and a decrease in the HCN1 channels protein expression in both hippocampus and prefrontal cortex. The phosphorylated extracellular regulated protein kinase 1/2 (p-ERK1/2), an important regulator of HCN channels, was also obviously reduced in hippocampus and prefrontal cortex of mice with METH re-exposure. Meanwhile, acute METH exposure did not affect the working memory function and the protein expressions of HCN1 channels and p-ERK1/2. Overall, our data firstly showed the aberrant protein expression of HCN1 channels in METH re-exposed mice with enhanced working memory, which was probably related to the down-regulation of p-ERK1/2 protein expression.

Background: Oligomeric amyloid-β peptide (Aβ) is associated with dysfunctional neuronal networks and neuronal loss in the development of Alzheimer's disease (AD). Ischemic postconditioning protects against post-ischemic excitotoxicity, oxidative stress, and inflammatory process that have also been implicated in the pathogenesis of AD. Evaluating the roles of ischemic postconditioning in oligomeric Aβ-induced neurotoxicity and underlying signal events may provide potential strategy for medical therapy in AD., Objectives: The aim of the present study was to explore whether and how a brief ischemic postconditioning protects against Aβ neurotoxicity in rat hippocampus., Methods: Oligomeric Aβ25-35 (20 nmol/rat) or Aβ1-42 (5 nmol/rat) was infused by intracerebroventricular injection in adult male Sprague-Dawley rats. Ischemic postconditioning, a brief episode of global brain ischemia (3 min), was conducted at 1, 3, or 7 days after Aβ treatment, respectively., Results: A brief ischemic postconditioning reduced neuronal loss and inhibited the activation of MLK3, MKK3/6, and P38MAPKs in rat hippocampal CA1 and CA3 subfields after Aβ oligomer infusion. An N-methyl-D-aspartate (NMDA) receptor antagonist amantadine, but not non-NMDA receptor antagonist CNQX, reversed the MLK3-MKK3/6-P38MAPK signal events and beneficial effect of ischemic postconditioning on neuronal survival. Such reversion was also realized by NVP-AAM077, a GluN2A-subunit-selective NMDA receptor antagonist. Moreover, posttreatment with low doses of NMDA (5 nmol-40 nmol/rat) suppressed the Aβ-induced P38MAPK signaling and imitated the neuroprotection of ischemic postconditioning against Aβ neurotoxicity., Conclusions: Ischemic postconditioning provides neuroprotection against Aβ neurotoxicity by moderate upregulation of NMDA receptor signaling, especially GluN2A-containing NMDA receptor pathway, and thereafter downregulation of MLK3-MKK3/6-P38MAPK signal events.

Metabolic disorders induce adverse effects on brain functions. The hippocampus is one of the most vulnerable regions to metabolic disorders. Disrupted neuroplasticity is a major cause of hippocampus-related behavioral impairments, including memory loss, anxiety, and depression. Astrocytes support processes of neuroplasticity. However, whether metabolic disorders induce changes in astrocytes and their roles in affective disorders is relatively unclear. To answer this question, we fed 8-week-old male C57BL/6 mice with a high-fat diet (HFD) for 12 weeks to induce metabolic disruption and then examined their performance of hippocampus-related memory, and anxiety- and depression-like behaviors. The morphology of astrocytes and the expression of astrocytic neuroplasticity-related proteins in the hippocampus were also assessed. The results showed that HFD led to obesity, systemic insulin resistance and dysregulated lipid metabolism in mice. HFD induced depression-like behaviors, but not anxiety or memory impairment. Furthermore, HFD increased the expression of GFAP, shortened the processes of GFAP + cells, and downregulated the expression of astrocytic neuroplasticity-related protein, GLAST, GLT-1, and connexin-43 in the hippocampi. In conclusion, HFD disturbs the function of hippocampal astrocytes and induces depression-like behaviors in mice. A decrease of hippocampal glutamate transporters may play a critical role in the pathogenesis of metabolic disorder-related depression., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Fear memory is important for the survival of animals and is associated with certain anxiety disorders, such as posttraumatic stress disorder. A thorough understanding of the molecular mechanisms of fear memory, especially associative fear memory, is imperative. MicroRNA-138 (miR-138) is a widely distributed microRNA in the brain and is locally enriched at synaptic sites. The role of miR-138 in the formation of fear memory is still largely unknown. In this study, a contextual fear conditioning (CFC) paradigm, bioinformatic methods, a luciferase assay, real-time PCR and western blot were used to evaluate the detailed effects of miR-138 on fear memory. We found that miR-138 transiently decreased in the dorsal hippocampus (DH) after CFC training. Upregulation or downregulation of miR-138 in the DH with miR-138 agomir or antagomir treatment significantly impaired or enhanced the formation of CFC memory, respectively. Moreover, the effects of miR-138 in the DH on the formation of CFC memory were achieved by changing the expression of the downstream target gene calpain 1 (Capn1). Taken together, both the in-vitro evidence and the in-vivo evidence presented in this study support the involvement of miR-138 in CFC memory formation, at least partly via the regulation of Capn1-mediated synaptic plasticity changes. Therapeutic use of miR-138/Capn1 is promising as an alternative option in the treatment of fear memory-related anxiety disorders.

The brain undergoes several anatomical, biochemical, and molecular changes during aging, which subsequently result in downregulation of synaptic plasticity genes and decline of memory. However, the regulation of these genes during aging is not clearly understood. Previously, we reported that the expression of histone deacetylase (HDAC)2 was upregulated in the hippocampus of old mice and negatively correlated with the decline in recognition memory. As HDAC2 regulates key synaptic plasticity neuronal immediate early genes (IEGs), we have examined their expression and epigenetic regulation. We noted that the expression of neuronal IEGs decreased both at mRNA and protein level in the hippocampus of old mice. To explore the underlying regulation, we analyzed the binding of HDAC2 and level of histone acetylation at the promoter of neuronal IEGs. While the binding of HDAC2 was higher, H3K9 and H3K14 acetylation level was lower at the promoter of these genes in old as compared to young and adult mice. Further, we inhibited HDAC2 non-specifically by sodium butyrate and specifically by antisense oligonucleotide to recover epigenetic modification, expression of neuronal IEGs, and memory in old mice. Inhibition of HDAC2 increased histone H3K9 and H3K14 acetylation level at the promoter of neuronal IEGs, their expression, and recognition memory in old mice as compared to control. Thus, inhibition of HDAC2 can be used as a therapeutic target to recover decline in memory due to aging and associated neurological disorders.

Oxidative stress and amyloid-β (Aβ) oligomers have been implicated in Alzheimer's disease (AD). The growth and maintenance of neuronal networks are influenced by brain derived neurotrophic factor (BDNF) expression, which is promoted by protein kinase C epsilon (PKCɛ). We investigated the reciprocal interaction among oxidative stress, Aβ, and PKCɛ levels and subsequent PKCɛ-dependent MnSOD and BDNF expression in hippocampal pyramidal neurons. Reduced levels of PKCɛ, MnSOD, and BDNF and an increased level of Aβ were also found in hippocampal neurons from autopsy-confirmed AD patients. In cultured human primary hippocampal neurons, spherical aggregation of Aβ (amylospheroids) decreased PKCɛ and MnSOD. Treatment with t-butyl hydroperoxide (TBHP) increased superoxide, the oxidative DNA/RNA damage marker, 8-OHG, and Aβ levels, but reduced PKCɛ, MnSOD, BDNF, and cultured neuron density. These changes were reversed with the PKCɛ activators, bryostatin and DCPLA-ME. PKCɛ knockdown suppressed PKCɛ, MnSOD, and BDNF but increased Aβ. In cultured neurons, the increase in reactive oxygen species (ROS) associated with reduced PKCɛ during neurodegeneration was inhibited by the SOD mimetic MnTMPyP and the ROS scavenger NAc, indicating that strong oxidative stress suppresses PKCɛ level. Reduction of PKCɛ and MnSOD was prevented with the PKCɛ activator bryostatin in 5-6-month-old Tg2576 AD transgenic mice. In conclusion, oxidative stress and Aβ decrease PKCɛ expression. Reciprocally, a depression of PKCɛ reduces BDNF and MnSOD, resulting in oxidative stress. These changes can be prevented with the PKCɛ-specific activators.

Aims: Alzheimer's disease (AD), a progressive development dementia, is increasingly impacting patients' living conditions worldwide. Despite medical care and funding support, there are still no highly individualized drugs and practical strategies for clinical prevention and treatment. Developmentally regulated brain protein (abbreviated as Drebrin or Dbn, also known as Dbn1 in mouse) exists in neurons, especially in dendrites, and is an actin-binding protein that modulates synaptic morphology and long-term memory. However, the majority of previous studies have focused on its upstream proteins and neglected the impact Drebrin has on behavior and AD in vivo., Methods: Here, we tracked the behavioral performances of 4-, 8-, 12-, and 16-month-old AD mice and investigated the expression level of Drebrin in their hippocampi. A Pearson correlation analysis between Drebrin levels and behavioral data was performed. Subsequently, 2-month-old AD mice were injected with rAAV-zsGreen-Dbn1 vector, composing the APP/PS1-Dbn1 group, and sex- and age-matched AD mice were injected with rAAV-tdTomato vector to serve as the control group. All mice were conducted behavioral tests and molecular detection 6 months later., Results: (i) The expression of Drebrin is decreased in the hippocampus of aged AD mice compared with that of age-matched WT and young adult AD mice; (ii) cognitive ability of APP/PS1 mice decreases with age; (iii) Drebrin protein expression in the hippocampus correlates with behavioral performance in different aged AD mice; (iv) cognitive ability improved significantly in APP/PS1-Dbn1 mice; (v) the expression level of Drebrin in APP/PS1-Dbn1 mouse hippocampus was significantly increased; (vi) the pathological lesion of AD was alleviated in APP/PS1-Dbn1 mice; (vii) the filamentous actin (F-actin) and microtubule-associated protein 2(MAP-2) in APP/PS1-Dbn1 mice were notably more than control mice., Conclusion: In this study, an effective expression of Drebrin improves cognitive abilities and alleviates lesions in an AD mouse model. These results may provide some valid resources for therapy and research of AD., (© 2017 John Wiley & Sons Ltd.)

Downregulation of GABAergic synaptic transmission contributes to the increase in overall excitatory activity in the ischemic brain. A reduction of GABA A receptor (GABA A R) surface expression partly accounts for this decrease in inhibitory activity, but the mechanisms involved are not fully elucidated. In this work, we investigated the alterations in GABA A R trafficking in cultured rat hippocampal neurons subjected to oxygen/glucose deprivation (OGD), an in vitro model of global brain ischemia, and their impact in neuronal death. The traffic of GABA A R was evaluated after transfection of hippocampal neurons with myc-tagged GABA A R β3 subunits. OGD decreased the rate of GABA A R β3 subunit recycling and reduced the interaction of the receptors with HAP1, a protein involved in the recycling of the receptors. Furthermore, OGD induced a calpain-mediated cleavage of HAP1. Transfection of hippocampal neurons with HAP1A or HAP1B isoforms reduced the OGD-induced decrease in surface expression of GABA A R β3 subunits, and HAP1A maintained the rate of receptor recycling. Furthermore, transfection of hippocampal neurons with HAP1 significantly decreased OGD-induced cell death. These results show a key role for HAP1 protein in the downmodulation of GABAergic neurotransmission during cerebral ischemia, which contributes to neuronal demise.

Insulin resistance is known to be a risk factor for cognitive impairment, most likely linked to insulin signaling, microglia overactivation, and beta amyloid (Aβ) deposition in the brain. Exenatide, a long lasting glucagon-like peptide-1 (GLP-1) analogue, enhances insulin signaling and shows neuroprotective properties. Pioglitazone, a peroxisome proliferated-activated receptor-γ (PPAR-γ) agonist, was previously reported to enhance cognition through its effect on Aβ accumulation and clearance. In the present study, insulin resistance was induced in male rats by drinking fructose for 12 weeks. The effect of monotherapy with pioglitazone (10 mg·kg(-1)) and exenatide or their combination on memory dysfunction was determined and some of the probable underlying mechanisms were studied. The current results confirmed that (1) feeding male rats with fructose syrup for 12 weeks resulted in a decline of learning and memory registered in eight-arm radial maze test; (2) treatment with pioglitazone or exenatide enhanced cognition, reduced hippocampal neurodegeneration, and reduced hippocampal microglia expression and beta amyloid oligomer deposition in a manner that is equal to monotherapies. These results may give promise for the use of pioglitazone or exenatide for ameliorating the learning and memory deficits associated with insulin resistance in clinical setting.

Previous studies have shown that inhibitors of the Na(+)/Ca(2+) exchanger (NCX) attenuate seizure activity in drug-induced epilepsy models, but the role of NCX in epilepsy is not fully understood. The present study examined the effects of pentylenetetrazole (PTZ)-induced kindling on the mRNA expression of NCX isoforms (NCX1, NCX2 and NCX3) in mouse brain. Chronic administration of PTZ at 40mg/kg resulted in kindling seizure development. It caused decreases in the mRNA levels of NCX1 and NCX2, but not NCX3, in the hippocampus. Changes in NCX isoform expression levels were not observed in the prefrontal cortex or striatum. Acute PTZ at 40mg/kg, which caused little seizure activity, also decreased NCX2, but not NCX1 mRNA levels in the hippocampus. These results suggest that down-regulation of hippocampal NCX1 expression is associated with PTZ-induced kindling seizure development., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Schizophrenia patients treated with olanzapine, or other second-generation antipsychotics, frequently develop metabolic side-effects, such as glucose intolerance and increased adiposity. We previously observed that modeling these adverse effects in rodents also resulted in hippocampal shrinkage. Here, we investigated the impact of olanzapine treatment, and the beneficial influence of routine exercise, on the neurosecretion machinery of the hippocampus. Immunodensities and interactions of three soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins (syntaxin-1, synaptosome-associated protein of 25kDa (SNAP-25) and vesicle-associated membrane protein (VAMP)), synaptotagmin and complexins-1/2 were quantified in the hippocampus of sedentary and exercising rats exposed over 9weeks to vehicle (n=28) or olanzapine (10mg/kg/day, n=28). In addition, brain sections from subgroups of sedentary animals (n=8) were co-immunolabeled with antibodies against vesicular GABA (VGAT) and glutamate (VGLUT1) transporters, along with syntaxin-1, and examined by confocal microscopy to detect selective olanzapine effects within inhibitory or excitatory terminals. Following olanzapine treatment, sedentary, but not exercising rats showed downregulated (33-50%) hippocampal densities of SNARE proteins and synaptotagmin, without altering complexin levels. Strikingly, these effects had no consequences on the amount of SNARE protein-protein interactions. Lower immunodensity of presynaptic proteins was associated with reduced CA1 volume and glucose intolerance. Syntaxin-1 depletion appeared more prominent in VGAT-positive terminals within the dentate gyrus, and in non-VGAT/VGLUT1-overlapping areas of CA3. The present findings suggest that chronic exposure to olanzapine may alter hippocampal connectivity, especially in inhibitory terminals within the dentate gyrus, and along the mossy fibers of CA3. Together with previous studies, we propose that exercise-based therapies might be beneficial for patients being treated with olanzapine., (Copyright © 2015 IBRO. Published by Elsevier Ltd. All rights reserved.)

Major depressive disorder (MDD) is a prevalent psychiatric mood illness and a major cause of disability and suicide worldwide. However, the underlying pathophysiology of MDD remains poorly understood due to its heterogenic nature. Extensive pre-clinical research suggests that many molecular alterations associated with MDD preferentially localize to the postsynaptic density (PSD). Here, we used a rodent chronic mild stress (CMS) model to generate susceptible and unsusceptible subpopulations. Proteomic analysis using an isobaric tag for relative and absolute quantitation (iTRAQ) and tandem mass spectrometry was performed to identify differentially expressed proteins in enriched PSD preparations from the hippocampi of different groups. More than 1500 proteins were identified and quantified, and 74 membrane proteins were differentially expressed. Of these membrane proteins, 51 (69%) were identified by SynaptomeDB search as having a predicted PSD localization. The unbiased profiles identified several PSD candidate proteins that may be related to CMS vulnerability or insusceptibility, and these two CMS phenotypes displayed differences in the abundance of several types of proteins. A detailed protein functional analysis pointed to a role for PSD-associated proteins involved in signaling and regulatory functions. Within the PSD, the N-methyl-D-aspartate (NMDA) receptor subunit NR2A and its downstream targets contribute to CMS susceptibility. Further analysis of disease relevance indicated that the PSD contains a complex set of proteins of known relevance to mental illnesses including depression. In sum, these findings provide novel insights into the contribution of PSD-associated proteins to stress susceptibility and further advance our understanding of the role of hippocampal synaptic plasticity in MDD., (Copyright © 2015 IBRO. Published by Elsevier Ltd. All rights reserved.)

In the adult brain, canonical Wnt (Wnt/β-catenin) signaling modulates neuronal function, hippocampal neurogenesis, and synaptic plasticity. Indeed, growing evidence suggests that downregulation of Wnt signaling could be involved in the cognitive decline associated with aging and also with the physiopathology of Alzheimer's disease (AD). However, the molecular basis remains unknown. At present, SAMP8 is an experimental model that has been proposed for studying age-related neurodegenerative changes associated with aging and the pathogenesis of AD. Here, we examined Wnt signaling in the hippocampus of SAMP8 mice at 9 and 12 months of age, as well as in its control-strain SAMR1 mice. Our results showed increased Dickkopf-1 protein levels in SAMP8 with age, in addition to GSK-3 α/β activation and hyperphosphorylated tau. Consequently, higher β-catenin phosphorylation at Ser(33,37) and Thr(41), which promotes its degradation, along with a decrease in active β-catenin (ABC) in the nucleus, were observed in SAMP8, mainly at the age of 12 months. Moreover, nuclear levels of Dvl3 were lower in 9- and 12-month-old SAMP8 mice. Related to these findings, SAMP8 showed an increase in neuronal loss in the hippocampus that was associated with lower protein levels of the antiapoptotic protein and the Wnt target gene, Bcl-2, in addition to an increase in the proapototic protein Bax. Our results suggest a relationship between age-related downregulation of canonical Wnt signaling and neuronal loss observed in the hippocampus of SAMP8 mice. Thus, enhancing Wnt signaling may represent a novel neuroprotective strategy aimed at counteracting the cognitive decline that is associated not only with aging but also with AD., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Activation of microglia may facilitate age-related impairment in cognitive functions including hippocampal-dependent memory. Considerable evidence indicates that hippocampal-derived estrogen improves hippocampal-dependent learning and memory. We hypothesize that activated microglia may inhibit de novo hippocampal estrogen synthesis and in turn suppress hippocampal synaptic protein expression. The present study aimed to elucidate the role of lipopolysaccharide (LPS)-activated microglial HAPI cells on estrogen synthesis and expression of synaptic proteins using H19-7 hippocampal neurons with a neuron-microglia co-culture system. LPS induced expression of the microglial activation markers major histocompatibility complex II (MHC II), CD11b, and ionized calcium-binding adapter molecule 1 (Iba1). Prolonged LPS exposure also enhanced the secretion of interleukin (IL)-6 and nitric oxide (NO) from microglial HAPI cells. Exposure to either LPS-activated microglia or IL-6, significantly suppressed the expression of synaptic proteins and the secretion of de novo hippocampal estrogen in H19-7 hippocampal neurons. In addition, LPS-activated microglia also decreased the expression of estrogen receptors (ERα and ERβ) in H19-7 hippocampal neurons. Our findings demonstrate a potential mechanism of microglia activation underlying the reduction in estrogen-mediated signaling on synaptic proteins in hippocampal neurons, which may be involved in hippocampal-dependent memory formation., (Copyright © 2014 Elsevier Inc. All rights reserved.)

We found that mRNA of MET, the receptor of hepatocyte growth factor (HGF), is significantly decreased in the hippocampus of Alzheimer's disease (AD) patients. Therefore, we tried to determine the cellular component-dependent changes of MET expressions. In this study, we examined cellular distribution of MET in the cerebral neocortices and hippocampi of 12 AD and 11 normal controls without brain diseases. In normal brains, MET immunoreactivity was observed in the neuronal perikarya and a subpopulation of astrocytes mainly in the subpial layer and white matter. In AD brains, we found marked decline of MET in hippocampal pyramidal neurons and granule cells of dentate gyrus. The decline was more obvious in the pyramidal neurons of the hippocampi than that in the neocortical neurons. In addition, we found strong MET immunostaining in reactive astrocytes, including those near senile plaques. Given the neurotrophic effects of the HGF/MET pathway, this decline may adversely affect neuronal survival in AD cases. Because it has been reported that HGF is also up-regulated around senile plaques, β-amyloid deposition might be associated with astrocytosis through the HGF signaling pathway., (© 2014 Japanese Society of Neuropathology.)

Deposition of extracellular amyloid-β (Aβ) peptide is one of the pathological hallmarks of Alzheimer's disease (AD). Accumulation of Aβ is thought to associate with cognition deficits, neuroinflammation and apoptosis observed in AD. However, effective neuroprotective approaches against Aβ neurotoxicity are unavailable. In the present study, we analysed the effects of pranlukast, a selective cysteinyl leukotriene receptor 1 (CysLT₁R) antagonist, on the impairment of learning and memory formation induced by Aβ and the probable underlying electrophysiological and molecular mechanisms. We found that bilateral intrahippocampal injection of Aβ₁₋₄₂ resulted in a significant decline of spatial learning and memory of mice in the Morris water maze (MWM) and Y-maze tests, together with a serious depression of in vivo hippocampal long-term potentiation (LTP) in the CA1 region of the mice. Importantly, this treatment caused significant increases in CysLT₁R expression and subsequent NF-κB signaling, caspase-3 activation and Bcl-2 downregulation in the hippocampus or prefrontal cortex. Oral administration of pranlukast at 0.4 or 0.8 mg/kg for 4 wk significantly reversed Aβ₁₋₄₂-induced impairments of cognitive function and hippocampal LTP in mice. Furthermore, pranlukast reversed Aβ₁₋₄₂-induced CysLT₁R upregulation, and markedly suppressed the Aβ₁₋₄₂-triggered NF-κB pathway, caspase-3 activation and Bcl-2 downregulation in the hippocampus and prefrontal cortex in mice. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay confirmed its presence in the brain after oral administration of pranlukast in mice. These data disclose novel findings about the therapeutic potential of pranlukast, revealing a previously unknown therapeutic possibility to treat memory deficits associated with AD.

Age-related decrease of testosterone levels in blood and brain is believed to be associated with neurodegenerative diseases such as Alzheimer's disease. However, the effect of testosterone on brain function is not well understood. Therefore, we investigated the impact of testosterone deprivation on mitochondrial gene expression in the brain of male gonadectomized (GDX) rats. We found that peripheral castration led to testosterone deficiency in the brain and caused a significant reduction in protein and mRNA expression of genes encoded by mitochondrial DNA, namely NADPH dehydrogenase subunit 1, subunit 4, cytochrome b, and cytochrome c oxidase subunit 1 and subunit 3 in the hippocampus. In addition, gene expression of peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α), which is a master regulator of mitochondrial biogenesis, and its downstream transcriptional factors, nuclear respiratory factors 1 and 2 and mitochondrial transcription factors A and B2, were also decreased in the hippocampus of GDX rats. These reductions in the expression of mitochondrial gene and transcriptional coactivators and factors were recovered by androgen replacement. These findings indicate that androgen plays an important role in mitochondrial gene expression in the hippocampus.

We investigated localization of Phospholipase C beta (PLCβ1 and PLCβ4) in laminaes of dorsal hippocampus and different subtypes of hippocampal interneurons in normal Kunming mouse, and their progressive changes during pilocarpine induced status epilepticus (SE) by quantitative immunohistochemistry and real time PCR. PLCβ1 was observed in the pyramidal layer of CA1-3 area, hilus of the dentate gyrus, whereas PLCβ4 was mainly expressed in calcium binding protein positive interneurons, i.e. calbindin, calretinin, parvalbumin positive interneurons in the strata oriens, radiatum of the CA area and hilus of the dentate gyrus. During pilocarpine induced SE, a temporary down-regulation of PLCβ4 in the interneurons of CA area at SE 30min, and a progressive reduction of PLCβ1/PLCβ4 in dentate hilar cells were demonstrated. These findings confirm and extend the regional specific distribution of PLCβ1 and PLCβ4 immunoreactivity in mouse hippocampus, and suggest that PLCβ1 and PLCβ4 may play an important role in maintenance of the status epilepticus., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Since aberrant miRNA expression has been implicated in numerous brain diseases, we studied miRNA expression and miRNA regulation of important signaling pathways during temporal lobe epileptogenesis in order to identify possible targets for epilepsy therapy. The temporal profile of miRNA expression was analyzed in three brain regions (CA1; dentate gyrus, DG; parahippocampal cortex, PHC) associated with epileptogenesis in a rat model for temporal lobe epilepsy. Tissue was obtained after electrically-induced status epilepticus (SE) at 1day (n=5), 1week (n=5) and 3-4months (n=5), and compared with control tissue (n=10) using the Exiqon microRNA arrays which contain capture probes targeting all miRNAs for rat (p<0.01, and a 1.5 fold up- or downregulation). Expression of three blood plasma miRNAs from the same group of rats was also investigated in rats in order to determine whether plasma miRNAs could serve as potential biomarkers of the epileptogenic process. Molecular pathways potentially altered by the expression of multiple miRNAs were identified using a web-based algorithm, DIANA. In CA1 and DG, more upregulated than downregulated miRNAs were present during each stage after SE. The highest numbers of upregulated miRNAs were encountered during the chronic stage in the DG. In PHC, a high number of downregulated miRNAs were detected. Key pathways involved, based upon quantitatively altered miRNA expression were: axon guidance, MAPK signaling pathway, focal adhesion, TGFβ, ErbB-, Wnt- and mTOR signaling, and regulation of actin skeleton. Expression of plasma miRNAs was differentially regulated after induction of SE. This study identified several signaling pathways possibly involved in temporal lobe epileptogenesis, not previously indicated by RNA microarray studies. These include miRNAs that regulate the ErbB and Wnt pathways and focal adhesion, which may represent interesting new targets for therapeutic interventions., (© 2013.)

Objective: To explore the effects of exposure to aluminum (Al) on long-term potentiation (LTP) and AMPA receptor subunits in rats in vivo., Methods: Different dosages of aluminum-maltolate complex [Al(mal)3] were given to rats via acute intracerebroventricular (i.c.v.) injection and subchronic intraperitoneal (i.p.) injection. Following Al exposure, the hippocampal LTP were recorded by field potentiation technique in vivo and the expression of AMPAR subunit proteins (GluR1 and GluR2) in both total and membrane-enriched extracts from the CA1 area of rat hippocampus were detected by Western blot assay., Results: Acute Al treatment produced dose-dependent suppression of LTP in the rat hippocampus and dose-dependent decreases of GluR1 and GluR2 in membrane extracts; however, no similar changes were found in the total cell extracts, which suggests decreased trafficking of AMPA receptor subunits from intracellular pools to synaptic sites in the hippocampus. The dose-dependent suppressive effects on LTP and the expression of AMPA receptor subunits both in the membrane and in total extracts were found after subchronic Al treatment, indicating a decrease in AMPA receptor subunit trafficking from intracellular pools to synaptic sites and an additional reduction in the expression of the subunits., Conclusion: Al(mal)3 obviously and dose-dependently suppressed LTP in the rat hippocampal CA1 region in vivo, and this suppression may be related to both trafficking and decreases in the expression of AMPA receptor subunit proteins. However, the mechanisms underlying these observations need further investigation., (Copyright © 2014 The Editorial Board of Biomedical and Environmental Sciences. Published by China CDC. All rights reserved.)

Structural alterations in the limbic system, neuronal cell loss, and low levels of neurotrophins have been implicated in the pathogenesis of depression. While it is generally accepted that increasing monoamine levels in the brain can effectively alleviate depression, the precise neurobiological mechanisms involved are unclear. In the present study, we examined the effects of two antidepressants, duloxetine and mirtazapine, on the expression of apoptotic and neurotrophic proteins in the cerebral cortex and hippocampus of mice. Duloxetine (10 mg/kg) and mirtazapine (3 mg/kg) were chronically administered for 21 days, and qRT-PCR analysis was carried for the following: neurotrophins (BDNF, NGF, FGF-2, and NT-3); anti-apoptotic proteins (Bcl-2 and Bcl-xL) and pro-apoptotic proteins (Bax, Bad, and p53). Both duloxetine and mirtazapine produced antidepressant activity in the forced swimming test and induced increased cortical and hippocampal mRNA expression of BDNF. Duloxetine also increased Bcl-2, Bcl-xL, FGF-2, and NT-3 expression in the cerebral cortex, and FGF-2 expression in the hippocampus. Moreover, duloxetine reduced Bax and p53 expression in the hippocampus, and Bad expression in the cerebral cortex. Mirtazapine decreased Bcl-xL and Bax expression in the hippocampus, and Bad and p53 expression in both the hippocampus and cerebral cortex. Mirtazapine also increased the expression of neurotrophins, NGF and NT-3, in the cerebral cortex. These results suggest that duloxetine and mirtazapine could elicit their therapeutic effect by modulating the activity of apoptotic and neurotrophic pathways, thus enhancing plasticity and cell survival in depressive patients., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Background: Previous research in animal seizure models indicates that the pleiotropic cytokine TNF is an important effector/mediator of neuroinflammation and cell death. Recently, it has been demonstrated that TNF downregulates Klotho (KL) through the nuclear factor kappa B (NFkB) system in animal models of chronic kidney disease and colitis. KL function in the brain is unclear, although Klotho knockout (Kl-/-) mice exhibit neural degeneration and a reduction of hippocampal synapses. Our aim was to verify if the triad KL-NFKB1-TNF is also dysregulated in temporal lobe epilepsy associated with hippocampal sclerosis (TLE(HS)) patients., Findings: We evaluated TNF, NFKB1 and KL relative mRNA expression levels by reverse transcription quantitative PCR (RT-qPCR) in resected hippocampal tissue samples from 14 TLE(HS) patients and compared them to five post mortem controls. Four reference genes were used: GAPDH, HPRT1, ENO2 and TBP. We found that TNF expression was dramatically upregulated in TLE(HS) patients (P <0.005). NFKB1 expression was also increased (P <0.03) while KL was significantly downregulated (P <0.03) in TLE(HS) patients. Hippocampal KL expression had an inverse correlation with NFKB1 and TNF., Conclusions: Our data suggest that, similar to other inflammatory diseases, TNF downregulates KL through NFkB in TLE(HS) patients. The remarkable TNF upregulation in patients is a strong indication of hippocampal chronic inflammation. Our finding of hippocampal KL downregulation has wide implications not only for TLE(HS) but also for other neuronal disorders related to neurodegeneration associated with inflammation.

Cognitive and motor performances decline during aging. Although it is clear that such signs reflect synaptic compromise, the underlying mechanisms have not been defined. We found that the levels and activity of the synaptic plasticity modulators phosphatidylinositol-(4,5)-bisphosphate (PI(4,5)P₂) and phospholipase Cγ (PLCγ) were substantially reduced in hippocampal synaptic membranes from old mice. In addition, these membranes contained reduced levels of the PI(4,5)P₂-clustering molecule myristoylated alanine-rich C kinase substrate (MARCKS). Consistent with a cause-effect relationship, raising MARCKS levels in the brain of old mice led to increased synaptic membrane clustering of PI(4,5)P₂ and to PLCγ activation. MARCKS overexpression in the hippocampus of old mice or intraventricular perfusion of MARCKS peptide resulted in enhanced long-term potentiation and improved memory. These results reveal one of the mechanisms involved in brain dysfunction during aging.

Insulin-like growth factor-1 (IGF-1) has been demonstrated to have neuroprotective effects, but little is known concerning its role in vascular dementia (VaD). This study aimed to evaluate expression of IGF-1 signaling in hippocampus in rat model of VaD, and probe the underlying mechanisms. Permanent occlusion of bilateral common carotid arteries (2-VO) was used as VaD model. Learning and memory functions were declined significantly in 2-VO rats, and these impairments were further deteriorated with the prolongation of 2-VO treatment. IGF-1, IGF-1 receptor (IGF-1R), total Akt and phosphorylated Akt (p-Akt) were all measured at 1, 2 and 4 months following 2-VO injury. Compared with controls, IGF-1, IGF-1 mRNA and p-Akt expression were significantly decreased in hippocampus of 2-VO rats. However, changes of IGF-1R and total Akt levels were not significant. These results suggest that down-regulation of IGF-1 and p-Akt may contribute to the impairments of learning and memory functions after 2-VO. IGF-1/IGF-1R signaling system may involved in the onset and development of VaD., (Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.)

The possibility that the degeneration of hippocampal neurons can be caused by mis-regulation of Wnt/β-catenin signaling was tested. Downregulation of Wnt signaling by the inducible expression of Axin, ICAT, and dnTcf4E causes degeneration of hippocampal neurons, while upregulation of Wnt signaling by the inducible expression of Dvl and β-catenin has a negligible effect. Treatment with ICG-001, a small molecule known to inhibit Wnt signaling, causes degeneration of hippocampal neurons, while the treatment with a JNK specific inhibitor does not show any effect. The results from LDH and TUNEL assays suggest that degeneration occurs via apoptotic processes. Inhibition of Wnt signaling reduced IGF-1 expression and the addition of IGF-1 blocked degeneration, which suggests that downregulation of IGF-1/Akt signaling is partially responsible for the degeneration. Inducible expression of Axin in the hippocampal neurons isolated from Axin2P-rtTA/pBI-EGFP-Axin double transgenic mice also causes degeneration. Consistent with the findings, these mice had more neuronal cell death in hippocampus and had differences in contextual conditioning upon the inducible expression of Axin. In summary, our data strongly support the idea that downregulation of Wnt/β-catenin signaling causes degeneration of hippocampal neurons in vivo and may be a cause of neurodegenerative diseases related to an anxiety related response., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Anaphase-promoting complex (APC) and its coactivator Cdh1 are required for maintaining cells in G1 phase of cell cycle in proliferating cells. Recent studies showed that Cdh1-APC was active in post-mitotic neurons, which regulates neuronal survival, differentiation, axonal growth and synaptic development. However, the possible function of Cdh1-APC in ischemic brain injury has not been determined. This study aimed to investigate changes in the activity of Cdh1-APC in hippocampus after global cerebral ischemia in rat. We found that, compared with sham group, the expression of Cdh1 in hippocampus was significantly decreased on 1 and 3 days of reperfusion in ischemia group (P<0.05), while neuronal apoptosis were found in hippocampal CA1 region and the two downstream substrates of Cdh1-APC (SnoN and Skp2) were significantly increased after global cerebral ischemia (P<0.05). This study demonstrates that the down-regulation of Cdh1-APC is associated with neuronal apoptosis in hippocampus following global cerebral ischemia. It brings a prospect to explore the further function of Cdh1-APC in the injured nervous system., (Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.)

The study determined whether there were gender differences in the expression of hippocampal genes in adult rats in association with dissimilarity in their behavior, and how these were affected by prenatal stress. Pregnant Wistar rats were subjected to varied stress once daily on days 14-20 of gestation. Adult female offspring of control rats showed significantly less anxiogenic behavior in the elevated plus maze and better discrimination between a novel and familiar object than males in the object recognition test. These gender differences in behavior were markedly attenuated by prenatal stress. Using Affymetrix DNA chip technology on hippocampal extracts prepared from littermates of the offspring used for behavioral tests, we found that 1,680 genes were differentially expressed in control males and females. The gender difference in gene expression was decreased to 11% (191 genes) by prenatal stress. In both sexes, processes like the translational machinery, mitochondrial activity, and cation transport were downregulated compared to controls, but there was a greater suppression of genes involved in vesicle trafficking, regulation of synaptic plasticity, and neurogenesis in females than in males. This was compensated by a higher expression of other components of vesicle trafficking, microtubule-based processes, and neurite development. Prenatal stress decreased the expression of 19 Rab proteins in females and five Rabs in males, but a compensatory increase of Rab partner proteins and effectors only occurred in females. Exposure to stress decreased the expression of synaptic proteins, synaptophysin, and synaptopodin in prenatally stressed males and females and increased those of PSD-95 and NR1 subunit of the N-methyl-D-aspartic acid (NMDA) glutamate receptor only in females. The study provides an unbiased view of key genes and proteins that act as gender dependent molecular sensors. The disruption of their expression by adverse early life stress may explain the alterations that occur in behavior., (Copyright © 2010 Wiley-Liss, Inc.)

Gephyrin, which is a postsynaptic scaffolding protein participated in clustering GABA(A) receptors at inhibitory synapses, has been reported to be involved in temporal lobe epilepsy (TLE) recently. Here, we investigate gephyrin protein expression in the temporal lobe epileptic foci in epileptic patients and experimental animals in order to explore the probable relationship between gephyrin expression and TLE. Using immunohistochemistry, immunofluorescence, and western blot analysis, gephyrin expression was examined in 30 human temporal neocortex samples from patients who underwent surgery to treat drug-refractory TLE and 10 histological normal temporal neocortex from the controls. Meanwhile, we investigated the gephyrin expression in the hippocampus and adjacent neocortex from experimental rats on 24 h, 48 h, 1 week, 2 weeks, 1 month, and 2 months postseizure and from control rats. Gephyrin protein was mainly expressed in the membrane and cytoplasm of neurons in temporal lobe epileptic foci in humans and experimental rats. Gephyrin expression was significantly lower in the temporal neocortex of TLE patients compared to the controls. In experimental rats, the expression of gephyrin in temporal lobe was downregulated in epileptic groups compared to the control group. Gephyrin expression gradually decreased during the acute period and the latent period, but then began to increase below the levels seen in controls during the chronic phase. Our findings suggest that gephyrin may be involved in the development of TLE., (Copyright © 2011 Wiley-Liss, Inc.)

The current study uses an extended access rat model of cocaine self-administration (5-h session per day, 14 days), which elicits several features manifested during the transition to human addiction, to study the neural adaptations associated with cocaine withdrawal. Given that the hippocampus is thought to have an important role in maintaining addictive behavior and appears to be especially relevant to mechanisms associated with withdrawal, this study attempted to understand how extended access to cocaine impacts the hippocampus at the cellular and molecular levels, and how these alterations change over the course of withdrawal (1, 14, and 28 days). Therefore, at the cellular level, we examined the effects of cocaine withdrawal on cell proliferation (Ki-67+ and NeuroD+ cells) in the DG. At the molecular level, we employed a 'discovery' approach with gene expression profiling in the DG to uncover novel molecules possibly implicated in the neural adaptations that take place during cocaine withdrawal. Our results suggest that decreased hippocampal cell proliferation might participate in the adaptations associated with drug removal and identifies 14 days as a critical time-point of cocaine withdrawal. At the 14-day time-point, gene expression profiling of the DG revealed the dysregulation of several genes associated with cell fate regulation, highlighting two new neurobiological correlates (Ascl-1 and Dnmt3b) that accompany cessation of drug exposure. Moreover, the results point to Fas-Associated protein with Death Domain (FADD), a molecular marker previously associated with the propensity to substance abuse and cocaine sensitization, as a key cell fate regulator during cocaine withdrawal. Identifying molecules that may have a role in the restructuring of the hippocampus following substance abuse provides a better understanding of the adaptations associated with cocaine withdrawal and identifies novel targets for therapeutic intervention.

Rats deprived of social contact with other rats at a young age experience a form of prolonged stress that leads to long-lasting changes in behavioral profile. Such isolation is thought to be anxiogenic for these normally gregarious animals, and the abnormal reactivity of isolated rats to environmental stimuli is thought to be a product of prolonged stress. We now show that isolation of rats at weaning reduced immobility time in the forced swim test, decreased sucrose intake and preference, and down-regulated both brain-derived neurotrophic factor (BDNF) and activity-regulated cytoskeletal associated protein (Arc) in the hippocampus. In the Morris water maze, isolated rats showed a reduced latency to reach the hidden platform during training, indicative of an improved learning performance, compared with group-housed rats. The cumulative search error during place training trials indicated a reliable difference between isolated and group-housed rats on days 4 and 5. The probe trial revealed a significant decrease of the average proximity to the target location in the isolated rats suggesting an improvement in spatial memory. Isolated rats also showed an increase in the plasma level of corticosterone on the 5th day of training and increased expression of BDNF and Arc in the hippocampus on both days 1 and 5. These results show that social isolation from weaning in rats results in development of depressive-like behavior but has a positive effect on spatial learning, supporting the existence of a facilitating effect of stress on cognitive function., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Epidemiological studies estimate that greater than 60% of the adult US population may be categorized as either overweight or obese and there is a growing appreciation that obesity affects the functional integrity of the central nervous system (CNS). We recently developed a lentivirus (LV) vector that produces an insulin receptor (IR) antisense RNA sequence (IRAS) that when injected into the hypothalamus selectively decreases IR signaling in hypothalamus, resulting in increased body weight, peripheral adiposity and plasma leptin levels. To test the hypothesis that this obesity/hyperleptinemic phenotype would impair hippocampal synaptic transmission, we examined short term potentiation (STP) and long term potentiation (LTP) in the hippocampus of rats that received the LV-IRAS construct or the LV-Control construct in the hypothalamus (hypo-IRAS and hypo-Con, respectively). Stimulation of the Schaffer collaterals elicits STP that develops into LTP in the CA1 region of hypo-Con rats; conversely, hypo-IRAS rats exhibit STP that fails to develop into LTP. To more closely examine the potential role of hyperleptinemia in these electrophysiological deficits, hypo-IRAS were subjected to mild food restriction paradigms that would either: 1) prevent the development of the obesity phenotype; or 2) reverse an established obesity phenotype in hypo-IRAS rats. Both of these paradigms restored LTP in the CA1 region and reversed the decreases in the phosphorylated/total ratio of GluA1 Ser845 AMPA receptor subunit expression observed in the hippocampus of hypo-IRAS rats. Collectively, these data support the hypothesis that obesity impairs hippocampal synaptic transmission and support the hypothesis that these deficits are mediated through the impairment of hippocampal leptin activity., (Copyright © 2010 Elsevier Inc. All rights reserved.)

Recent studies suggest that blood-brain barrier (BBB) permeability contributes to epileptogenesis in symptomatic epilepsies. We have previously described angiogenesis, aberrant vascularization, and BBB alteration in drug-refractory temporal lobe epilepsy. Here, we investigated the role of vascular endothelial growth factor (VEGF) in an in vitro integrative model of vascular remodeling induced by epileptiform activity in rat organotypic hippocampal cultures. After kainate-induced seizure-like events (SLEs), we observed an overexpression of VEGF and VEGF receptor-2 (VEGFR-2) as well as receptor activation. Vascular density and branching were significantly increased, whereas zonula occludens 1 (ZO-1), a key protein of tight junctions (TJs), was downregulated. These effects were fully prevented by VEGF neutralization. Using selective inhibitors of VEGFR-2 signaling pathways, we found that phosphatidylinositol 3-kinase is involved in cell survival, protein kinase C (PKC) in vascularization, and Src in ZO-1 regulation. Recombinant VEGF reproduced the kainate-induced vascular changes. As in the kainate model, VEGFR-2 and Src were involved in ZO-1 downregulation. These results showed that VEGF/VEGFR-2 initiates the vascular remodeling induced by SLEs and pointed out the roles of PKC in vascularization and Src in TJ dysfunction, respectively. This suggests that Src pathway could be a therapeutic target for BBB protection in epilepsies.

The molecular mechanisms underlying the behavioral effects of glucocorticoids are poorly understood. We report here that hippocampal neuronal nitric oxide synthase (nNOS) is a crucial mediator. Chronic mild stress and glucocorticoids exposures caused hippocampal nNOS overexpression via activating mineralocorticoid receptor. In turn, hippocampal nNOS-derived nitric oxide (NO) significantly downregulated local glucocorticoid receptor expression through both soluble guanylate cyclase (sGC)/cGMP and peroxynitrite (ONOO(-))/extracellular signal-regulated kinase signal pathways, and therefore elevated hypothalamic corticotrophin-releasing factor, a peptide that governs the hypothalamic-pituitary-adrenal axis. More importantly, nNOS deletion or intrahippocampal nNOS inhibition and NO-cGMP signaling blockade (using NO scavenger or sGC inhibitor) prevented the corticosterone-induced behavioral modifications, suggesting that hippocampal nNOS is necessary for the role of glucocorticoids in mediating depressive behaviors. In addition, directly delivering ONOO(-) donor into hippocampus caused depressive-like behaviors. Our findings reveal a role of hippocampal nNOS in regulating the behavioral effects of glucocorticoids.

Background: Stress results in hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis, characterized by increased central CRF activity, elevated circulating glucocorticoid levels, impaired glucocorticoid-mediated negative feedback and abnormal hippocampal functions, possibly contributing to the development of behavioral pathologies, such as depression. The hippocampus is critically involved in the control of the HPA axis as well as in explicit memory, contextual aspects of fear, organization of the behavioral response to environmental novelty and in habituation. We have previously shown that mice that over-express CRF in the brain exhibit impaired novelty detection and altered psychophysiological and behavioral habituation, functions linked to dopamine receptor-dependent hippocampal plasticity., Objective and Methods: Therefore, the aim of the present study was to measure D1 and D2 dopamine receptor expression and related signaling, such as CREB and ERK protein levels and phosphorylation, in the hippocampus and other brain regions of mice with post-natal CRF over-expression (CRF-OE mice)., Results: We found a region-specific down-regulation of both D1 and D2 protein expression, without altered CRF receptor protein expression, in the hippocampus in CRF-OE mice. This was accompanied by an impaired phosphorylation of hippocampal CREB, but not ERK1 and ERK2, in the same animals., Conclusions: These results suggest that post-natal onset CRF over-expression results in an impairment of dopamine signaling in the hippocampus, which may underlie cognitive and motivational aspects of stress-related, CRF-driven mood disorders.

5-Hydroxytryptamine (5-HT) is involved in a variety of different physiological processes and behaviors through the activation of equally diverse receptors subtypes. In this work we studied the changes on the expression of 5-HT(5A) receptors in rat hippocampus induced by leptin, an adipocyte-derived hormone that has been reported to participate in the modulation of food intake and in adult hippocampal neurogenesis. To study the effect of leptin on the 5-HT(5A) receptor gene expression a qRT-PCR was used and the distribution of those receptors in the hippocampus was visualized by immunohistochemistry. Rats were separated in four groups: control (untreated rats), leptin-treated, serotonin-treated and leptin+serotonin treated. The results showed that even though the 5-HT(5A) gene expression did not change in the hippocampus of any of the treated groups, in the rats treated with leptin and serotonin, the specific immunostaining for the 5-HT(5A) serotonin receptor decreased significantly in the dentate gyrus., (Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.)

While both 17β-estradiol (E2) and progesterone (P4) are neuroprotective in several experimental paradigms, P4 also counteracts E2 neuroprotective effects. We recently reported that a 4-h treatment of cultured hippocampal slices with P4 following a prolonged (20 h) treatment with E2 eliminated estrogenic neuroprotection against NMDA toxicity and induction of brain-derived neurotrophic factor (BDNF) expression. In the present study, we evaluated the effects of the same treatment on levels of estrogen receptors, ERα and ERβ, and BDNF using a similar paradigm. E2 treatment resulted in elevated ERβ mRNA and protein levels, did not modify ERα mRNA, but increased ERα protein levels, and increased BDNF mRNA levels. P4 reversed E2-elicited increases in ERβ mRNA and protein levels, in ERα protein levels, and in BDNF mRNA levels. Experiments with an ERβ-specific antagonist, PHTPP, and specific agonists of ERα and ERβ, propylpyrazoletriol and diarylpropionitrile, respectively, indicated that E2-mediated neuroprotection against NMDA toxicity was, at least in part, mediated via ERβ receptor. In support of this conclusion, E2 did not protect against NMDA toxicity in cultured hippocampal slices from ERβ-/- mice. Thus, E2-mediated neuroprotection against NMDA toxicity may be because of estrogenic induction of BDNF via its ERβ receptor, and P4-mediated inhibition of E2 neuroprotective effects treatment to P4-induced down-regulation of ERβ and BDNF., (© 2010 The Authors. Journal of Neurochemistry © 2010 International Society for Neurochemistry.)

Introduction: Uptake of glutamate in the hippocampus by specialized transporters appears to be important for the prevention of glutamate-induced neurotoxicity. However, the role of these transporters in synaptic plasticity and learning is still unclear. We examined the expression pattern of glutamate transporters at different stages of spatial learning using a one-day (three blocks) version of the Morris Water Maze., Methods: Male rats (Sprague Dawley, 3 months old) were divided into three groups (learner, swim control, or naïve control) and animals were sacrificed after the first, second, or third block of training. The hippocampi were immediately extracted and flash frozen for RNA analysis. Real time polymerase chain reaction was employed to examine the expression of glutamate transporter 1 (Glt-1), Glt1b, glutamate-aspartate transporter (GLAST) and excitatory amino acid carrier-1 (EAAC1) in whole hippocampi., Results: EAAC1 and GLAST RNA were downregulated in the learner and swimmer groups (compared to naïve) after the first two blocks of training during the one-day protocol but EAAC1 returned to control levels by the end of the third block. GLAST levels were upregulated by the third block of training. Glt-1b expression was downregulated during the second block of training but returned to control by the third block., Conclusions: The observed decreases in glutamate transporter expression may be important during the early stages of spatial learning as a possible mechanism to enhance glutamatergic availability during critical stages of learning. However, similar decreases in glutamate transporter expression in both the learner and swimmer groups indicate that the observed differences may be task-induced. Additional experiments are currently underway to examine this possibility.

Prenatal exposure to inflammatory stimuli is known to influence adult brain function. In addition, adult hippocampal neurogenesis is impaired by a local pro-inflammatory microenvironment. On this basis, we hypothesized that a pro-inflammatory insult during gestation would have negative effects on adult neurogenesis in the offspring. Pregnant Wistar rats received subcutaneous injections of lipopolysaccharide (LPS; 0.5mg/kg) or saline every other day from gestational day 14 to 20. The adult offspring prenatally treated with LPS showed a decrease in the proliferating cells and the newborn neurons of the dentate gyrus. Furthermore, prenatal LPS treatment impaired performance in the neurogenesis-dependent novel object recognition test. Maternal care was impaired by prenatal LPS administration but did not contribute to the effects of prenatal LPS on adult neurogenesis. Persistent microglial activation and downregulated expression of transforming growth factor beta-1 (TGFβ(1)) occurred specifically in the adult hippocampus of animals treated prenatally with LPS. Importantly, chronic hippocampal TGFβ(1) overexpression restored neurogenesis as well as recognition memory performance to control levels. These findings demonstrate that prenatal inflammation triggered by LPS impairs adult neurogenesis and recognition memory. Furthermore, we provide a model of reduced adult neurogenesis with long-lasting defined alterations in the neurogenic niche. Finally, we show that the expression of a single cytokine (TGFβ(1)) in the hippocampus can restore adult neurogenesis and its related behavior, highlighting the role of TGFβ(1) in these processes., (Copyright © 2010 Elsevier Inc. All rights reserved.)

In the adult mouse, signaling through c-Jun N-terminal kinases (JNKs) links exposure to acute stress to various physiological responses. Inflammatory cytokines, brain injury and ischemic insult, or exposure to psychological acute stressors induce activation of hippocampal JNKs. Here we report that exposure to acute stress caused activation of JNKs in the hippocampal CA1 and CA3 subfields, and impaired contextual fear conditioning. Conversely, intrahippocampal injection of JNKs inhibitors sp600125 (30 μm) or D-JNKI1 (8 μm) reduced activity of hippocampal JNKs and rescued stress-induced deficits in contextual fear. In addition, intrahippocampal administration of anisomycin (100 μg/μl), a potent JNKs activator, mimicked memory-impairing effects of stress on contextual fear. This anisomycin-induced amnesia was abolished after cotreatment with JNKs selective inhibitor sp600125 without affecting anisomycin's ability to effectively inhibit protein synthesis as measured by c-Fos immunoreactivity. We also demonstrated milder and transient activation of the JNKs pathway in the CA1 subfield of the hippocampus during contextual fear conditioning and an enhancement of contextual fear after pharmacological inhibition of JNKs under baseline conditions. Finally, using combined biochemical and transgenic approaches with mutant mice lacking different members of the JNK family (Jnk1, Jnk2, and Jnk3), we provided evidence that JNK2 and JNK3 are critically involved in stress-induced deficit of contextual fear, while JNK1 mainly regulates baseline learning in this behavioral task. Together, these results support the possibility that hippocampal JNKs serve as a critical molecular regulator in the formation of contextual fear.

Obstructive sleep apnea (OSA) is a common sleep and breathing disorder characterized by repeated episodes of hypoxemia. OSA causes neurocognitive deficits including perception and memory impairment but the underlying mechanisms are unknown. Here we show that in a mouse model of OSA, chronic intermittent hypoxia treatment impairs both early- and late-phase long-term potentiation (LTP) in the hippocampus. In intermittent hypoxia-treated mice the excitability of CA1 neurons was reduced and hippocampal brain-derived neurotrophic factor (BDNF) was down-regulated. We further showed that exogenous application of BDNF restored the magnitude of LTP in hippocampal slices from hypoxia-treated mice. In addition, microinjection of BDNF into the brain of the hypoxic mice prevented the impairment in LTP. These data suggest that intermittent hypoxia impairs hippocampal neuronal excitability and reduces the expression of BDNF leading to deficits in LTP and memory formation. Thus, BDNF level may be a novel therapeutic target for alleviating OSA-induced neurocognitive deficits., ((c) 2010 Elsevier Inc. All rights reserved.)

Several lines of evidence suggest a dysfunctional glutamate system in major depressive disorder (MDD). Recently, we reported reduced levels of metabotropic glutamate receptor subtype 5 (mGluR5) in postmortem brains in MDD, however the neurobiological mechanisms that induce these abnormalities are unclear. In the present study, we examined the effect of chronic corticosterone (CORT) administration on the expression of mGluR5 protein and mRNA in the rat frontal cortex and hippocampus. Rats were injected with CORT (40 mg/kg s.c.) or vehicled once daily for 21 days. The expression of mGluR5 protein and mRNA was assessed by Western blotting and quantitative real-time PCR (qPCR). In addition, mGluR1 protein was measured in the same animals. The results revealed that while there was a significant reduction (-27%, P=0.0006) in mGluR5 protein expression in the hippocampus from CORT treated rats, mRNA levels were unchanged. Also unchanged were mGluR5 mRNA and protein levels in the frontal cortex and mGluR1 protein levels in both brain regions. Our findings provide the first evidence that chronic CORT exposure regulates the expression of mGluR5 and are in line with previous postmortem and imaging studies showing reduced mGluR5 in MDD. Our findings suggest that elevated levels of glucocorticoids may contribute to impairments in glutamate neurotransmission in MDD., ((c) 2010 IBRO. Published by Elsevier Ltd. All rights reserved.)

Cognitive deficits are a common feature of major depression (MD), with largely unknown biological underpinnings. In addition to the affective and cognitive symptoms of MD, a dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis is commonly observed in these patients. Increased plasma glucocorticoid levels are known to render the hippocampus susceptible to neuronal damage. This structure is important for learning and memory, creating a potential link between HPA axis dysregulation and cognitive deficits in depression. In order to further elucidate how altered stress responsiveness may contribute to the etiology of MD, three mouse lines with high (HR), intermediate (IR), or low (LR) stress reactivity were generated by selective breeding. The aim of the present study was to investigate whether increased stress reactivity is associated with deficits in hippocampus-dependent memory tests. To this end, we subjected mice from the HR, IR, and LR breeding lines to tests of recognition memory, spatial memory, and depression-like behavior. In addition, measurements of brain-derived neurotrophic factor (BDNF) in the hippocampus and plasma of these animals were conducted. Our results demonstrate that HR mice exhibit hippocampus-dependent memory deficits along with decreased hippocampal, but not plasma, BDNF levels. Thus, the stress reactivity mouse lines are a promising animal model of the cognitive deficits in MD with the unique feature of a genetic predisposition for an altered HPA axis reactivity, which provides the opportunity to explore the progression of the symptoms of MD, predisposing genetic factors as well as new treatment strategies., (Copyright 2009 Elsevier Ltd. All rights reserved.)

Background: Developmental iodine deficiency results in inadequate thyroid hormone (TH), which damages the hippocampus. Here, we explored the roles of hippocampal doublecortin and neural cell adhesion molecule (NCAM)-180 in developmental iodine deficiency and hypothyroidism., Methods: Two developmental rat models were established with either an iodine-deficient diet, or propylthiouracil (PTU)-adulterated water (5 ppm or 15 ppm) to impair thyroid function, in pregnant rats from gestational day 6 until postnatal day (PN) 28. Silver-stained neurons and protein levels of doublecortin and NCAM-180 in several hippocampal subregions were assessed on PN14, PN21, PN28, and PN42., Results: The results show that nerve fibers in iodine-deficient and 15 ppm PTU-treated rats were injured on PN28 and PN42. Downregulation of doublecortin and upregulation of NCAM-180 were observed in iodine-deficient and 15 ppm PTU-treated rats from PN14 on. These alterations were irreversible by the restoration of serum TH concentrations on PN42., Conclusion: Developmental iodine deficiency and hypothyroidism impair the expression of doublecortin and NCAM-180, leading to nerve fiber malfunction and thus impairments in hippocampal development.