Assessment of spatial memory in mice

Effects of developmental exposure to bisphenol A on spatial navigational learning and memory in rats: A CLARITY-BPA study

Bisphenol A (BPA) is a ubiquitous industrial chemical used in the production of a wide variety of items. Previous studies suggest BPA exposure may result in neuro-disruptive effects; however, data are inconsistent across animal and human studies. As part of the Consortium Linking Academic and Regulatory Insights on BPA Toxicity (CLARITY-BPA), we sought to determine whether female and male rats developmentally exposed to BPA demonstrated later spatial navigational learning and memory deficits. Pregnant NCTR Sprague-Dawley rats were orally dosed from gestational day 6 to parturition, and offspring were directly orally dosed until weaning (postnatal day 21). Treatment groups included a vehicle control, three BPA doses (2.5μg/kg body weight (bw)/day-[2.5], 25μg/kg bw/day-[25], and 2500μg/kg bw/day-[2500]) and a 0.5μg/kg/day ethinyl estradiol (EE)-reference estrogen dose. At adulthood, 1/sex/litter was tested for seven days in the Barnes maze. The 2500 BPA group sniffed more incorrect holes on day 7 than those in the control, 2.5 BPA, and EE groups. The 2500 BPA females were less likely than control females to locate the escape box in the allotted time (p value=0.04). Although 2.5 BPA females exhibited a prolonged latency, the effect did not reach significance (p value=0.06), whereas 2.5 BPA males showed improved latency compared to control males (p value=0.04), although the significance of this result is uncertain. No differences in serum testosterone concentration were detected in any male or female treatment groups. Current findings suggest developmental exposure of rats to BPA may disrupt aspects of spatial navigational learning and memory.

Influence of age-related learning and memory capacity of mice: different effects of a high and low caloric diet

BACKGROUND

Recent studies indicate that consumption of the different calorie diet may be an important way to accelerate or slow the neurodegenerative disorder related to age. Long-term consumption of a high-calorie diet affects the brain and increase the risk of neurodegenerative disorders. And consumption of a low-calorie diet (caloric restriction, CR) could delay aging, and protect the central nervous system from neurodegenerative disorders. The underlying mechanisms have not yet been clearly defined.

METHOD

Thirty 6-week-old C57/BL6 mice were randomly assigned to a NC group (fed standard diet, n = 10), a CR group (fed a low-calorie diet, n = 10) or a HC group (fed a high-calorie diet, n = 10) for 10 months. Body weight was measured monthly. Learning and memory capacity were determined by Morris water maze. Pathological changes of the hippocampus cells were detected with HE and Nissl staining. The expression of GFAP was determined by immunofluorescence and western blot. The expression of mTOR, S6K and LC3B in the hippocampus was determined by immunofluorescence.

RESULTS

After feeding for 10 months, compared with mice in the NC group, mean body weight was significantly higher in the HC group and significantly lower in the CR group. The result of Morris water maze showed that compared with mice in the NC group, the learning and memory capacity was significantly increased in the CR group, and significantly decreased in the HC group. HE and Nissl staining of the hippocampus showed cells damaged obviously in the HC group. In the hippocampus, the expression of GFAP, mTOR and S6K was increased in the HC group, and decreased in the CR group. The expression of LC3B was decreased in the HC group, and increased in the CR group.

CONCLUSIONS

Long-term consumption of a high-calorie diet could inhibit autophagy function, and facilitate neuronal loss in the hippocampus, which in turn aggravate age-related cognition impairment. And consumption of a low-calorie diet (caloric restriction, CR) could enhance the degree of autophagy, protect neurons effectively against aging and damage, and keep learning and memory capacity better.

Physical exercise counteracts MPTP-induced changes in neural precursor cell proliferation in the hippocampus and restores spatial learning but not memory performance in the water maze

Parkinson's disease (PD) is characterized by a continuous loss of dopaminergic neurons in the substantia nigra, which not only leads to characteristic motor symptoms but also to cognitive impairments. Physical exercise has been shown to improve hippocampus-dependent cognitive functions in PD patients. Animal studies have demonstrated the involvement of adult hippocampal neurogenesis in exercise-induced improvements of visuo-spatial learning and memory. Here, we investigated the direct impact of voluntary wheel running on hippocampal neurogenesis and spatial learning and memory in the Morris water maze (MWM) using the1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD. We also analyzed striatal and hippocampal dopamine transmission and mRNA expression levels of dopamine receptors. We show that MPTP-induced spatial learning deficits were alleviated by short-term physical exercise but not MPTP-induced spatial memory impairments in either exercise intervention group. Neural precursor proliferation was transiently altered in MPTP-treated mice, while the cell survival was increased by exercise. Dopamine was progressively depleted by MPTP and its turnover altered by exercise. In addition, gene expression of dopamine receptor D1/D5 was transiently upregulated following MPTP treatment but not affected by physical exercise. Our findings suggest that physical exercise benefits spatial learning but not memory performance in the MWM after MPTP-induced dopamine depletion by restoring precursor cell proliferation in the hippocampus and influencing dopamine transmission. This adds to the understanding of cognitive decline and mechanisms for potential improvements by physical exercise in PD patients.

Unraveling cognitive traits using the Morris water maze unbiased strategy classification (MUST-C) algorithm

The assessment of spatial cognitive learning in rodents is a central approach in neuroscience, as it enables one to assess and quantify the effects of treatments and genetic manipulations from a broad perspective. Although the Morris water maze (MWM) is a well-validated paradigm for testing spatial learning abilities, manual categorization of performance in the MWM into behavioral strategies is subject to individual interpretation, and thus to biases. Here we offer a support vector machine (SVM) - based, automated, MWM unbiased strategy classification (MUST-C) algorithm, as well as a cognitive score scale. This model was examined and validated by analyzing data obtained from five MWM experiments with changing platform sizes, revealing a limitation in the spatial capacity of the hippocampus. We have further employed this algorithm to extract novel mechanistic insights on the impact of members of the Toll-like receptor pathway on cognitive spatial learning and memory. The MUST-C algorithm can greatly benefit MWM users as it provides a standardized method of strategy classification as well as a cognitive scoring scale, which cannot be derived from typical analysis of MWM data.

Autophagy Modulation by Lanthionine Ketimine Ethyl Ester Improves Long-Term Outcome after Central Fluid Percussion Injury in the Mouse

Diffuse axonal injury is recognized as a progressive and long-term consequence of traumatic brain injury. Axonal injury can have sustained negative consequences on neuronal functions such as anterograde and retrograde transport and cellular processes such as autophagy that depend on cytoarchitecture and axon integrity. These changes can lead to somatic atrophy and an inability to repair and promote plasticity. Obstruction of the autophagic process has been noted after brain injury, and rapamycin, a drug used to stimulate autophagy, has demonstrated positive effects in brain injury models. The optimization of drugs to promote beneficial autophagy without negative side effects could be used to attenuate traumatic brain injury and promote improved outcome. Lanthionine ketimine ethyl ester, a bioavailable derivative of a natural sulfur amino acid metabolite, has demonstrated effects on autophagy both in vitro and in vivo. Thirty minutes after a moderate central fluid percussion injury and throughout the survival period, lanthionine ketimine ethyl ester was administered, and mice were subsequently evaluated for learning and memory impairments and biochemical and histological changes over a 5-week period. Lanthionine ketimine ethyl ester, which we have shown previously to modulate autophagy markers and alleviate pathology and slow cognitive decline in the 3 × TgAD mouse model, spared cognition and pathology after central fluid percussion injury through a mechanism involving autophagy modulation.

Influence of chewing behaviour on memory and spatial learning in albino BALB/c mice

INTRODUCTION

Since the relationship between chewing and cognitive functions has not been fully elucidated, this study aimed to determine the impact of chewing behaviour on spatial learning and memory in albino male BALB/c mice.

METHODS

Twenty mice aged 8 weeks were divided into 2 equal groups. The regular chewing group was fed with uncrushed grains (the same diet given to all 20 mice since they were weaned) and the limited chewing group was fed with crushed grains. At 16 weeks of age, the mice were evaluated over 5 days, including a 4-day acquisition phase prior to a probe test of spatial learning and memory in the Morris water maze on the fifth day.

RESULTS

A comparison of the regular chewing group and the limited chewing group found no significant differences in either the acquisition phase or the probe test. However, there were significant differences in the acquisition phase for just the regular chewing group when comparing results from the first day to those from the other 3 days.

CONCLUSIONS

The results suggest that regular chewing affects spatial learning and memory since mice in the regular chewing group decreased their times to find the hidden platform during the acquisition phase.

Hippocampal-dependent neurocognitive impairment following cranial irradiation observed in pre-clinical models: current knowledge and possible future directions

We reviewed the literature for studies pertaining to impaired adult neurogenesis leading to neurocognitive impairment following cranial irradiation in rodent models. This compendium was compared with respect to radiation dose, converted to equivalent dose in 2 Gy fractions (EQD2) to allow for direct comparison between studies. The effects of differences between animal species and the dependence on animal age as well as for time after irradiation were also considered. One of the major sites of de novo adult neurogenesis is the hippocampus, and as such, this review also focuses on assessing evidence related to the expression and potential effects of inflammatory cytokines on neural stem cells in the subgranular zone of the dentate gyrus and whether this correlates with neurocognitive impairment. This review also discusses potential strategies to mitigate the detrimental effects on neurogenesis and neurocognition resulting from cranial irradiation, and how the rationale for these strategies compares with the current outcome of pre-clinical studies.

Mouse hippocampal GABAB1 but not GABAB2 subunit-containing receptor complex levels are paralleling retrieval in the multiple-T-maze

GABAB receptors are heterodimeric G-protein coupled receptors known to be involved in learning and memory. Although a role for GABAB receptors in cognitive processes is evident, there is no information on hippocampal GABAB receptor complexes in a multiple T maze (MTM) task, a robust paradigm for evaluation of spatial learning. Trained or untrained (yoked control) C57BL/6J male mice (n = 10/group) were subjected to the MTM task and sacrificed 6 h following their performance. Hippocampi were taken, membrane proteins extracted and run on blue native PAGE followed by immunoblotting with specific antibodies against GABAB1, GABAB1a, and GABAB2. Immunoprecipitation with subsequent mass spectrometric identification of co-precipitates was carried out to show if GABAB1 and GABAB2 as well as other interacting proteins co-precipitate. An antibody shift assay (ASA) and a proximity ligation assay (PLA) were also used to see if the two GABAB subunits are present in the receptor complex. Single bands were observed on Western blots, each representing GABAB1, GABAB1a, or GABAB2 at an apparent molecular weight of approximately 100 kDa. Subsequently, densitometric analysis revealed that levels of GABAB1 and GABAB1a but not GABAB2- containing receptor complexes were significantly higher in trained than untrained groups. Immunoprecipitation followed by mass spectrometric studies confirmed the presence of GABAB1, GABAB2, calcium calmodulin kinases I and II, GluA1 and GluA2 as constituents of the complex. ASA and PLA also showed the presence of the two subunits of GABAB receptor within the complex. It is shown that increased levels of GABAB1 subunit-containing complexes are paralleling performance in a land maze.

Standardized Herbal Formula PM012 Decreases Cognitive Impairment and Promotes Neurogenesis in the 3xTg AD Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD) is a severe neurodegenerative disease for which there is currently no effective treatment. This study investigated whether treatment with the herbal formula PM012 would improve the cognitive function and the pathological features of AD in 3xTg-AD mice. The cognitive function of 3xTg-AD mice was assessed using the Morris water maze test and positron-emission tomography (PET) with 18 F-2 fluoro-2-deoxy-D-glucose ([F-18] FDG) neuroimaging. The levels of the amyloid beta (Aβ) deposits in the hippocampus were evaluated by immunohistochemistry. Neurogenesis was assessed by quantitative labeling with the DNA marker bromodeoxyuridine (BrdU) and the newborn neuron marker doublecortin (DCX). PM012 treatment significantly ameliorated memory deficit in AD mice, as shown by shortened escape latencies and increased time spent in the target zone during probe tests. In addition, PM012 significantly decreased Aβ deposits, up-regulated the expression of brain-derived neurotrophic factor (BDNF), increased neurogenesis, and improved brain glucose metabolism in the 3xTg-AD mice. These results suggest that PM012 could be a promising treatment for AD.

Oral TNFα Modulation Alters Neutrophil Infiltration, Improves Cognition and Diminishes Tau and Amyloid Pathology in the 3xTgAD Mouse Model

Cytokines such as TNFα can polarize microglia/macrophages into different neuroinflammatory types. Skewing of the phenotype towards a cytotoxic state is thought to impair phagocytosis and has been described in Alzheimer’s Disease (AD). Neuroinflammation can be perpetuated by a cycle of increasing cytokine production and maintenance of a polarized activation state that contributes to AD progression. In this study, 3xTgAD mice, age 6 months, were treated orally with 3 doses of the TNFα modulating compound isoindolin-1,3 dithione (IDT) for 10 months. We demonstrate that IDT is a TNFα modulating compound both in vitro and in vivo. Following long-term IDT administration, mice were assessed for learning & memory and tissue and serum were collected for analysis. Results demonstrate that IDT is safe for long-term treatment and significantly improves learning and memory in the 3xTgAD mouse model. IDT significantly reduced paired helical filament tau and fibrillar amyloid accumulation. Flow cytometry of brain cell populations revealed that IDT increased the infiltrating neutrophil population while reducing TNFα expression in this population. IDT is a safe and effective TNFα and innate immune system modulator. Thus small molecule, orally bioavailable modulators are promising therapeutics for Alzheimer’s disease.

Protein kinase D promotes plasticity-induced F-actin stabilization in dendritic spines and regulates memory formation

PKD regulates the stabilization of the F-actin network within dendritic spines upon chemically induced plasticity changes and is needed for proper hippocampal LTP and spatial memory formation.

Actin turnover in dendritic spines influences spine development, morphology, and plasticity, with functional consequences on learning and memory formation. In nonneuronal cells, protein kinase D (PKD) has an important role in stabilizing F-actin via multiple molecular pathways. Using in vitro models of neuronal plasticity, such as glycine-induced chemical long-term potentiation (LTP), known to evoke synaptic plasticity, or long-term depolarization block by KCl, leading to homeostatic morphological changes, we show that actin stabilization needed for the enlargement of dendritic spines is dependent on PKD activity. Consequently, impaired PKD functions attenuate activity-dependent changes in hippocampal dendritic spines, including LTP formation, cause morphological alterations in vivo, and have deleterious consequences on spatial memory formation. We thus provide compelling evidence that PKD controls synaptic plasticity and learning by regulating actin stability in dendritic spines.

The effect of GABA transporter 1 (GAT1) inhibitor, tiagabine, on scopolamine-induced memory impairments in mice

BACKGROUND

GABAergic neurotransmission is involved in long-term potentiation, a neurophysiological basis for learning and memory. On the other hand, GABA-enhancing drugs may impair memory and learning in humans and animals. The present study aims at investigating the effect of GAT1 inhibitor tiagabine on memory and learning.

METHODS

Albino Swiss (CD-1) and C57BL/6J mice were used in the passive avoidance (PA), Morris water maze (MWM) and radial arm water maze (RAWM) tasks. Scopolamine (1mg/kg ip) was applied to induce cognitive deficits.

RESULTS

In the retention trial of PA scopolamine reduced step-through latency as compared to vehicle-treated mice, and pretreatment with tiagabine did not have any influence on this effect. In MWM the results obtained for vehicle-treated mice, scopolamine-treated group and combined scopolamine+tiagabine-treated mice revealed variable learning abilities in these groups. Tiagabine did not impair learning in the acquisition trial. In RAWM on day 1 scopolamine-treated group made nearly two-fold more errors than vehicle-treated mice and mice that received combined scopolamine and tiagabine. Learning abilities in the latter group were similar to those of vehicle-treated mice in the corresponding trial block on day 1, except for the last trial block, during which tiagabine+scopolamine-injected mice made more errors than control mice and the scopolamine-treated group. In all groups a complete reversal of memory deficits was observed in the last trial block of day 2.

CONCLUSIONS

The lack of negative influence of tiagabine on cognitive functions in animals with scopolamine-induced memory impairments may be relevant for patients treated with this drug.

Bifidobacteria modulate cognitive processes in an anxious mouse strain

Increasing evidence suggests that a brain-gut-microbiome axis exists, which has the potential to play a major role in modulating behaviour. However, the role of this axis in cognition remains relatively unexplored. Probiotics, which are commensal bacteria offering potential health benefit, have been shown to decrease anxiety, depression and visceral pain-related behaviours. In this study, we investigate the potential of two Bifidobacteria strains to modulate cognitive processes and visceral pain sensitivity. Adult male BALB/c mice were fed daily for 11 weeks with B. longum 1714, B. breve 1205 or vehicle treatment. Starting at week 4, animals were behaviourally assessed in a battery of tests relevant to different aspects of cognition, as well as locomotor activity and visceral pain. In the object recognition test, B. longum 1714-fed mice discriminated between the two objects faster than all other groups and B. breve 1205-fed mice discriminated faster than vehicle animals. In the Barnes maze, B. longum 1714-treated mice made fewer errors than other groups, suggesting a better learning. In the fear conditioning, B. longum 1714-treated group also showed better learning and memory, yet presenting the same extinction learning profile as controls. None of the treatments affected visceral sensitivity. Altogether, these data suggest that B. longum 1714 had a positive impact on cognition and also that the effects of individual Bifidobacteria strains do not generalise across the species. Clinical validation of the effects of probiotics on cognition is now warranted.

Chronic BDNF deficiency leads to an age-dependent impairment in spatial learning

Brain-derived neurotrophic factor (BDNF) is a crucial mediator of neural plasticity and, consequently, of memory formation. In hippocampus-dependent learning tasks BDNF also seems to play an essential role. However, there are conflicting results concerning the spatial learning ability of aging BDNF(+/-) mice in the Morris water maze paradigm. To evaluate the effect of chronic BDNF deficiency in the hippocampus on spatial learning throughout life, we conducted a comprehensive study to test differently aged BDNF(+/-) mice and their wild type littermates in the Morris water maze and to subsequently quantify their hippocampal BDNF protein levels as well as expression levels of TrkB receptors. We observed an age-dependent learning deficit in BDNF(+/-) animals, starting at seven months of age, despite stable hippocampal BDNF protein expression and continual decline of TrkB receptor expression throughout aging. Furthermore, we detected a positive correlation between hippocampal BDNF protein levels and learning performance during the probe trial in animals that showed a good learning performance during the long-term memory test.

Deficits of psychomotor and mnesic functions across aging in mouse lemur primates

Owing to a similar cerebral neuro-anatomy, non-human primates are viewed as the most valid models for understanding cognitive deficits. This study evaluated psychomotor and mnesic functions of 41 young to old mouse lemurs (Microcebus murinus). Psychomotor capacities and anxiety-related behaviors decreased abruptly from middle to late adulthood. However, mnesic functions were not affected in the same way with increasing age. While results of the spontaneous alternation task point to a progressive and widespread age-related decline of spatial working memory, both spatial reference and novel object recognition (NOR) memory tasks did not reveal any tendency due to large inter-individual variability in the middle-aged and old animals. Indeed, some of the aged animals performed as well as younger ones, whereas some others had bad performances in the Barnes maze and in the object recognition test. Hierarchical cluster analysis revealed that declarative-like memory was strongly impaired only in 7 out of 25 middle-aged/old animals. These results suggest that this analysis allows to distinguish elder populations of good and bad performers in this non-human primate model and to closely compare this to human aging.

Recent development of multifunctional agents as potential drug candidates for the treatment of Alzheimer's disease

Alzheimer's disease (AD) is a complex and progressive neurodegenerative disorder. The available therapy is limited to the symptomatic treatment and its efficacy remains unsatisfactory. In view of the prevalence and expected increase in the incidence of AD, the development of an effective therapy is crucial for public health. Due to the multifactorial aetiology of this disease, the multi-target-directed ligand (MTDL) approach is a promising method in search for new drugs for AD. This review updates information on the development of multifunctional potential anti-AD agents published within the last three years. The majority of the recently reported structures are acetylcholinesterase inhibitors, often endowed with some additional properties. These properties enrich the pharmacological profile of the compounds giving hope for not only symptomatic but also causal treatment of the disease. Among these advantageous properties, the most often reported are an amyloid-β antiaggregation activity, inhibition of β-secretase and monoamine oxidase, an antioxidant and metal chelating activity, NOreleasing ability and interaction with cannabinoid, NMDA or histamine H3 receptors. The majority of novel molecules possess heterodimeric structures, able to interact with multiple targets by combining different pharmacophores, original or derived from natural products or existing therapeutics (tacrine, donepezil, galantamine, memantine). Among the described compounds, several seem to be promising drug candidates, while others may serve as a valuable inspiration in the search for new effective therapies for AD.

A novel unbiased counting method for the quantification of synapses in the mouse brain

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We describe a novel method for synapse quantification using electron microscopy.

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Nissl-stained vibratome sections allowed accurate brain region identification.

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Automatic microscope stage shifts using custom-made software excluded observer bias.

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The method showed altered synaptic features after environmental enrichment.

Background

The numerical density of synapses and their ultrastructural features are best assessed with electron microscopy. Counting is done within counting frames placed on a pair of sections (disector technique). But this requires that the thin sections are taken from comparable brain regions and the disectors are placed in a uniform random fashion. Small brain areas like the polymorph layer of the mouse dentate gyrus are difficult to encounter, and manually moving the microscope stage for placing the micrographs seems arbitrary.

New method

Here the polymorph layer was approximated with 20 μm thin, Nissl-stained vibratome sections. The subsequent vibratome section was processed for electron microscopy and serially thin sectioned. The microscope stage was moved using a random number generator, placing at least 20 disectors onto a pair of sections. The numerical synapse density, the numerical density of dense-core vesicles, and other ultrastructural features were compared between mice that had been kept in an enriched environment and mice kept under standard housing conditions.

Results

Environmental enrichment significantly decreased the numerical density of dense-core vesicles and synaptic cleft widths within the polymorph layer, associated with behavioral improvement in the Morris water maze, a hippocampus-dependent task of spatial learning and memory.

Comparison with existing methods

This procedure was easy to handle and enabled us to produce thin sections in small, defined brain areas. Furthermore, placing the disectors with random numbers excluded observer bias.

Conclusions

Our procedure provides an uncomplicated way of assessing numerical densities in small brain areas in an unbiased manner.

Neurotrophin receptor p75(NTR) mediates Huntington's disease-associated synaptic and memory dysfunction

Learning and memory deficits are early clinical manifestations of Huntington's disease (HD). These cognitive impairments have been mainly associated with frontostriatal HD pathology; however, compelling evidence provided by several HD murine models suggests that the hippocampus may contribute to synaptic deficits and memory dysfunction in HD. The neurotrophin receptor p75(NTR) negatively regulates spine density, which is associated with learning and memory; therefore, we explored whether disturbed p75(NTR) function in the hippocampus could contribute to synaptic dysfunction and memory deficits in HD. Here, we determined that levels of p75(NTR) are markedly increased in the hippocampus of 2 distinct mouse models of HD and in HD patients. Normalization of p75(NTR) levels in HD mutant mice heterozygous for p75(NTR) prevented memory and synaptic plasticity deficits and ameliorated dendritic spine abnormalities, likely through normalization of the activity of the GTPase RhoA. Moreover, viral-mediated overexpression of p75(NTR) in the hippocampus of WT mice reproduced HD learning and memory deficits, while knockdown of p75(NTR) in the hippocampus of HD mice prevented cognitive decline. Together, these findings provide evidence of hippocampus-associated memory deficits in HD and demonstrate that p75(NTR) mediates synaptic, learning, and memory dysfunction in HD.

The MK2/3 cascade regulates AMPAR trafficking and cognitive flexibility

The interplay between long-term potentiation and long-term depression (LTD) is thought to be involved in learning and memory formation. One form of LTD expressed in the hippocampus is initiated by the activation of the group 1 metabotropic glutamate receptors (mGluRs). Importantly, mGluRs have been shown to be critical for acquisition of new memories and for reversal learning, processes that are thought to be crucial for cognitive flexibility. Here we provide evidence that MAPK-activated protein kinases 2 and 3 (MK2/3) regulate neuronal spine morphology, synaptic transmission and plasticity. Furthermore, mGluR-LTD is impaired in the hippocampus of MK2/3 double knockout (DKO) mice, an observation that is mirrored by deficits in endocytosis of GluA1 subunits. Consistent with compromised mGluR-LTD, MK2/3 DKO mice have distinctive deficits in hippocampal-dependent spatial reversal learning. These novel findings demonstrate that the MK2/3 cascade plays a strategic role in controlling synaptic plasticity and cognition.

Value of water mazes for assessing spatial and egocentric learning and memory in rodent basic research and regulatory studies

Maneuvering safely through the environment is central to survival of all animals. The ability to do this depends on learning and remembering locations. This capacity is encoded in the brain by two systems: one using cues outside the organism (distal cues), allocentric navigation, and one using self-movement, internal cues and sometimes proximal cues, egocentric navigation. Allocentric navigation involves the hippocampus, entorhinal cortex, and surrounding structures (e.g., subiculum); in humans this system encodes declarative memory (allocentric, semantic, and episodic, i.e., memory for people, places, things, and events). This form of memory is assessed in laboratory animals by many methods, but predominantly the Morris water maze (MWM). Egocentric navigation involves the dorsal striatum and connected structures; in humans this system encodes routes and integrated paths and when over-learned becomes implicit or procedural memory. Several allocentric methods for rodents are reviewed and compared with the MWM with particular focus on the Cincinnati water maze (CWM). MWM advantages include minimal training, no food deprivation, ease of testing, reliable learning, insensitivity to differences in body weight and appetite, absence of non-performers, control methods for performance effects, repeated testing capability and other factors that make this test well-suited for regulatory studies. MWM limitations are also reviewed. Evidence-based MWM design and testing methods are presented. On balance, the MWM is arguably the preferred test for assessing learning and memory in basic research and regulatory studies and the CWM is recommended if two tests can be accommodated so that both allocentric (MWM) and egocentric (CWM) learning and memory can be effectively and efficiently assessed.

α-Melanocyte stimulating hormone prevents GABAergic neuronal loss and improves cognitive function in Alzheimer's disease

In Alzheimer's disease (AD), appropriate excitatory-inhibitory balance required for memory formation is impaired. Our objective was to elucidate deficits in the inhibitory GABAergic system in the TgCRND8 mouse model of AD to establish a link between GABAergic dysfunction and cognitive function. We sought to determine whether the neuroprotective peptide α-melanocyte stimulating hormone (α-MSH) attenuates GABAergic loss and thus improves cognition. TgCRND8 mice with established β-amyloid peptide pathology and nontransgenic littermates were treated with either α-MSH or vehicle via daily intraperitoneal injections for 28 d. TgCRND8 mice exhibited spatial memory deficits and altered anxiety that were rescued after α-MSH treatment. The expression of GABAergic marker glutamic acid decarboxylase 67 (GAD67) and the number of GABAergic GAD67+ interneurons expressing neuropeptide Y and somatostatin are reduced in the hippocampus in vehicle-treated TgCRND8 mice. In the septohippocampal pathway, GABAergic deficits are observed before cholinergic deficits, suggesting that GABAergic loss may underlie behavior deficits in vehicle-treated TgCRND8 mice. α-MSH preserves GAD67 expression and prevents loss of the somatostatin-expressing subtype of GABAergic GAD67+ inhibitory interneurons. Without decreasing β-amyloid peptide load in the brain, α-MSH improves spatial memory in TgCRND8 mice and prevents alterations in anxiety. α-MSH modulated the excitatory-inhibitory balance in the brain by restoring GABAergic inhibition and, as a result, improved cognition in TgCRND8 mice.

Effects of Fructus Akebiae on learning and memory impairment in a scopolamine-induced animal model of dementia

Fructus Akebiae (FAE) is a component of traditional Chinese medicines used for the clinical treatment of amnesia. The aim of the present study was to investigate the effects of FAE extract on scopolamine-induced learning and memory impairment in mice and Sprague-Dawley rats. Treatment with FAE (2.5, 5 and 10 mg/kg) was investigated in scopolamine-treated animals, and its effects on different types of memory were examined using the T-maze, the Morris water maze task, the novel object recognition test, the passive avoidance task and the step-down test. The results revealed that 5 and 10 mg/kg FAE attenuated scopolamine-mediated impairment of cognition, including spatial, episodic, aversive, and short- and long-term memory. Overall, these results suggest that FAE is an effective cognitive enhancer, and thus highlights the value of a multi-target strategy to address the complexity of cognitive dysfunction in Alzheimer’s disease.

The relationship between vestibular function and topographical memory in older adults

Research during the past two decades has demonstrated an important role of the vestibular system in topographical orientation and memory and the network of neural structures associated with them. Almost all of the supporting data have come from animal or human clinical studies, however. The purpose of the present study was to investigate the link between vestibular function and topographical memory in normal elderly humans. Twenty-five participants aged 70 to 85 years who scored from mildly impaired to normal on the Montreal Cognitive Assessment (MoCA) received three topographical memory tests: the Camden Topographical Recognition Memory Test (CTMRT), a computerized topographical mental rotation test (TMRT), and a virtual pond maze (VPM). They also received six vestibular or oculomotor tests: optokinetic nystagmus (OKN), visual pursuit (VP), actively generated vestibulo-ocular reflex (VOR), the sensory orientation test (SOT) for posture, and two measures of rotational memory (error in degrees, or RM°, and correct directional recognition, or RM→). The only significant bivariate correlations were among the three vestibular measures primarily assessing horizontal canal function (VOR, RM°, and RM→). A multiple regression analysis showed significant relationships between vestibular and demographic predictors and both the TMRT (R = 0.78) and VPM (R = 0.66) measures. The significant relationship between the vestibular and topographical memory measures supports the theory that vestibular loss may contribute to topographical memory impairment in the elderly.

Blueberry supplementation improves memory in middle-aged mice fed a high-fat diet

Consuming a high-fat diet may result in behavioral deficits similar to those observed in aging animals. It has been demonstrated that blueberry supplementation can allay age-related behavioral deficits. To determine if supplementation of a high-fat diet with blueberries offers protection against putative high-fat diet-related declines, 9-month-old C57Bl/6 mice were maintained on low-fat (10% fat calories) or high-fat (60% fat calories) diets with and without 4% freeze-dried blueberry powder. Novel object recognition memory was impaired by the high-fat diet; after 4 months on the high-fat diet, mice spent 50% of their time on the novel object in the testing trial, performing no greater than chance performance. Blueberry supplementation prevented recognition memory deficits after 4 months on the diets, as mice on this diet spent 67% of their time on the novel object. After 5 months on the diets, mice consuming the high-fat diet passed through the platform location less often than mice on low-fat diets during probe trials on days 2 and 3 of Morris water maze testing, whereas mice consuming the high-fat blueberry diet passed through the platform location as often as mice on the low-fat diets. This study is a first step in determining if incorporating more nutrient-dense foods into a high-fat diet can allay cognitive dysfunction.

Traumatic brain injury enhances neuroinflammation and lesion volume in caveolin deficient mice

Background

Traumatic brain injury (TBI) enhances pro-inflammatory responses, neuronal loss and long-term behavioral deficits. Caveolins (Cavs) are regulators of neuronal and glial survival signaling. Previously we showed that astrocyte and microglial activation is increased in Cav-1 knock-out (KO) mice and that Cav-1 and Cav-3 modulate microglial morphology. We hypothesized that Cavs may regulate cytokine production after TBI.

Methods

Controlled cortical impact (CCI) model of TBI (3 m/second; 1.0 mm depth; parietal cortex) was performed on wild-type (WT; C57Bl/6), Cav-1 KO, and Cav-3 KO mice. Histology and immunofluorescence microscopy (lesion volume, glia activation), behavioral tests (open field, balance beam, wire grip, T-maze), electrophysiology, electron paramagnetic resonance, membrane fractionation, and multiplex assays were performed. Data were analyzed by unpaired t tests or analysis of variance (ANOVA) with post-hoc Bonferroni’s multiple comparison.

Results

CCI increased cortical and hippocampal injury and decreased expression of MLR-localized synaptic proteins (24 hours), enhanced NADPH oxidase (Nox) activity (24 hours and 1 week), enhanced polysynaptic responses (1 week), and caused hippocampal-dependent learning deficits (3 months). CCI increased brain lesion volume in both Cav-3 and Cav-1 KO mice after 24 hours (P < 0.0001, n = 4; one-way ANOVA). Multiplex array revealed a significant increase in expression of IL-1β, IL-9, IL-10, KC (keratinocyte chemoattractant), and monocyte chemoattractant protein 1 (MCP-1) in ipsilateral hemisphere and IL-9, IL-10, IL-17, and macrophage inflammatory protein 1 alpha (MIP-1α) in contralateral hemisphere of WT mice after 4 hours. CCI increased IL-2, IL-6, KC and MCP-1 in ipsilateral and IL-6, IL-9, IL-17 and KC in contralateral hemispheres in Cav-1 KO and increased all 10 cytokines/chemokines in both hemispheres except for IL-17 (ipsilateral) and MIP-1α (contralateral) in Cav-3 KO (versus WT CCI). Cav-3 KO CCI showed increased IL-1β, IL-9, KC, MCP-1, MIP-1α, and granulocyte-macrophage colony-stimulating factor in ipsilateral and IL-1β, IL-2, IL-9, IL-10, and IL-17 in contralateral hemispheres (P = 0.0005, n = 6; two-way ANOVA) compared to Cav-1 KO CCI.

Conclusion

CCI caused astrocyte and microglial activation and hippocampal neuronal injury. Cav-1 and Cav-3 KO exhibited enhanced lesion volume and cytokine/chemokine production after CCI. These findings suggest that Cav isoforms may regulate neuroinflammatory responses and neuroprotection following TBI.

Barnes maze testing strategies with small and large rodent models

Spatial learning and memory of laboratory rodents is often assessed via navigational ability in mazes, most popular of which are the water and dry-land (Barnes) mazes. Improved performance over sessions or trials is thought to reflect learning and memory of the escape cage/platform location. Considered less stressful than water mazes, the Barnes maze is a relatively simple design of a circular platform top with several holes equally spaced around the perimeter edge. All but one of the holes are false-bottomed or blind-ending, while one leads to an escape cage. Mildly aversive stimuli (e.g. bright overhead lights) provide motivation to locate the escape cage. Latency to locate the escape cage can be measured during the session; however, additional endpoints typically require video recording. From those video recordings, use of automated tracking software can generate a variety of endpoints that are similar to those produced in water mazes (e.g. distance traveled, velocity/speed, time spent in the correct quadrant, time spent moving/resting, and confirmation of latency). Type of search strategy (i.e. random, serial, or direct) can be categorized as well. Barnes maze construction and testing methodologies can differ for small rodents, such as mice, and large rodents, such as rats. For example, while extra-maze cues are effective for rats, smaller wild rodents may require intra-maze cues with a visual barrier around the maze. Appropriate stimuli must be identified which motivate the rodent to locate the escape cage. Both Barnes and water mazes can be time consuming as 4-7 test trials are typically required to detect improved learning and memory performance (e.g. shorter latencies or path lengths to locate the escape platform or cage) and/or differences between experimental groups. Even so, the Barnes maze is a widely employed behavioral assessment measuring spatial navigational abilities and their potential disruption by genetic, neurobehavioral manipulations, or drug/ toxicant exposure.

Beneficial effects of multisensory and cognitive stimulation on age-related cognitive decline in long-term-care institutions

The aim of the present report was to evaluate the effectiveness and impact of multisensory and cognitive stimulation on improving cognition in elderly persons living in long-term-care institutions (institutionalized [I]) or in communities with their families (noninstitutionalized [NI]). We compared neuropsychological performance using language and Mini-Mental State Examination (MMSE) test scores before and after 24 and 48 stimulation sessions. The two groups were matched by age and years of schooling. Small groups of ten or fewer volunteers underwent the stimulation program, twice a week, over 6 months (48 sessions in total). Sessions were based on language and memory exercises, as well as visual, olfactory, auditory, and ludic stimulation, including music, singing, and dance. Both groups were assessed at the beginning (before stimulation), in the middle (after 24 sessions), and at the end (after 48 sessions) of the stimulation program. Although the NI group showed higher performance in all tasks in all time windows compared with I subjects, both groups improved their performance after stimulation. In addition, the improvement was significantly higher in the I group than the NI group. Language tests seem to be more efficient than the MMSE to detect early changes in cognitive status. The results suggest the impoverished environment of long-term-care institutions may contribute to lower cognitive scores before stimulation and the higher improvement rate of this group after stimulation. In conclusion, language tests should be routinely adopted in the neuropsychological assessment of elderly subjects, and long-term-care institutions need to include regular sensorimotor, social, and cognitive stimulation as a public health policy for elderly persons.

Single and repeated ultra-rapid detoxification prevents cognitive impairment in morphine addicted rats: a privilege for single detoxification

BACKGROUND

Opioids have been shown to affect learning and memory processes. Different protocols of morphine withdrawal can substantially vary in their success to prevent opioid induced impairments of cognitive performance. In the present study, we report the effects of single and repetitive ultra-rapid detoxification (URD) on spatial learning and memory in morphine addicted rats.

METHODS

Morphine (10 mg/kg) was intraperitoneally (IP) injected in male rats once a day over one week and after which they were detoxified with naloxone administration under anesthesia. For the repetitive procedure, a second one week morphine treatment with a second subsequent detoxification was performed. Control groups received an equivalent volume of saline injections. Spatial learning and memory was evaluated using the Morris water maze (MWM) task.

FINDINGS

Both protocols of morphine administration resulted in a severe spatial memory impairment that could be significantly prevented by both single and repetitive URD. However, memory abilities in animals treated with repetitive URD were still significantly lower than in animals of the corresponding control group. Alterations in motor activity or sensory-motor coordination between morphine treated and control animals could be ruled out by comparing swimming speed and visible platform performances that were not different between groups. Thus, URD and, specifically single URD, can prevent the spatial memory impairments in addicted rats.

CONCLUSION

As opioid addiction is an extending and serious concern in many societies, these findings may have clinical values and therapeutic implications for patients who experience multiple opioid relapses.

Assessing spatial learning and memory in rodents

Maneuvering safely through the environment is central to survival of almost all species. The ability to do this depends on learning and remembering locations. This capacity is encoded in the brain by two systems: one using cues outside the organism (distal cues), allocentric navigation, and one using self-movement, internal cues and nearby proximal cues, egocentric navigation. Allocentric navigation involves the hippocampus, entorhinal cortex, and surrounding structures; in humans this system encodes allocentric, semantic, and episodic memory. This form of memory is assessed in laboratory animals in many ways, but the dominant form of assessment is the Morris water maze (MWM). Egocentric navigation involves the dorsal striatum and connected structures; in humans this system encodes routes and integrated paths and, when overlearned, becomes procedural memory. In this article, several allocentric assessment methods for rodents are reviewed and compared with the MWM. MWM advantages (little training required, no food deprivation, ease of testing, rapid and reliable learning, insensitivity to differences in body weight and appetite, absence of nonperformers, control methods for proximal cue learning, and performance effects) and disadvantages (concern about stress, perhaps not as sensitive for working memory) are discussed. Evidence-based design improvements and testing methods are reviewed for both rats and mice. Experimental factors that apply generally to spatial navigation and to MWM specifically are considered. It is concluded that, on balance, the MWM has more advantages than disadvantages and compares favorably with other allocentric navigation tasks.

Spatial reversal learning is impaired by age in pet dogs

Aged dogs spontaneously develop progressive decline in both cognitive and behavioral function, in addition to neuropathological changes, that collectively parallel several aspects of human aging and Alzheimer's disease progression and likely contribute to the development of canine cognitive dysfunction syndrome. In the current study, ethologically relevant spatial learning, retention, and reversal learning tasks were conducted, with the goal of expanding canine neuropsychological testing to pet dogs. Initially, dogs (N = 44, aged 7.8 ± 2.8 years, mean ± SD) had to learn which of two alternative routes successfully led out of a T-maze. Two weeks later, long-term memory retention was assessed, immediately followed by a reversal learning task in which the previously correct route out of the maze was reversed compared with the initial learning and memory retention tasks. No effects of age were evident on the learning or retention tasks. However, older (≥ 8 years) dogs were significantly impaired on the reversal learning task compared with younger ones (< 8 years). Moreover, trial response latency was significantly increased in aged dogs across both the initial and reversal learning tasks but not on the retention task, which suggests that processing speed was impaired by increasing age during the acquisition of novel spatial information but not during performance of previously learned responses. Overall, the current study provides a framework for assessing cognitive function in pet dogs, which should improve understanding of the effects of aging on cognition in the dog population.

Exendin-4 induced glucagon-like peptide-1 receptor activation reverses behavioral impairments of mild traumatic brain injury in mice

Mild traumatic brain injury (mTBI) represents a major and increasing public health concern and is both the most frequent cause of mortality and disability in young adults and a chief cause of morbidity in the elderly. Albeit mTBI patients do not show clear structural brain defects and, generally, do not require hospitalization, they frequently suffer from long-lasting cognitive, behavioral, and emotional problems. No effective pharmaceutical therapy is available, and existing treatment chiefly involves intensive care management after injury. The diffuse neural cell death evident after mTBI is considered mediated by oxidative stress and glutamate-induced excitotoxicity. Prior studies of the long-acting GLP-1 receptor agonist, exendin-4 (Ex-4), an incretin mimetic approved for type 2 diabetes mellitus treatment, demonstrated its neurotrophic/protective activity in cellular and animal models of stroke, Alzheimer's and Parkinson's diseases, and, consequent to commonalities in mechanisms underpinning these disorders, Ex-4 was assessed in a mouse mTBI model. In neuronal cultures in this study, Ex-4 ameliorated H2O2-induced oxidative stress and glutamate toxicity. To evaluate in vivo translation, we administered steady-state Ex-4 (3.5 pM/kg/min) or saline to control and mTBI mice over 7 days starting 48 h prior to or 1 h post-sham or mTBI (30 g weight drop under anesthesia). Ex-4 proved well-tolerated and fully ameliorated mTBI-induced deficits in novel object recognition 7 and 30 days post-trauma. Less mTBI-induced impairment was evident in Y-maze, elevated plus maze, and passive avoidance paradigms, but when impairment was apparent Ex-4 induced amelioration. Together, these results suggest that Ex-4 may act as a neurotrophic/neuroprotective drug to minimize mTBI impairment.

Effects of Lactobacillus helveticus on murine behavior are dependent on diet and genotype and correlate with alterations in the gut microbiome

Modulation of the gut microbiota with diet and probiotic bacteria can restore intestinal homeostasis in inflammatory conditions and alter behavior via the gut-brain axis. The purpose of this study was to determine whether the modulatory effects of probiotics differ depending on diet and mouse genotype. At weaning, wild type (WT) and IL-10 deficient (IL-10(-/-)) 129/SvEv mice were placed on a standard mouse chow or a Western-style diet (fat 33%, refined carbohydrate 49%)±Lactobacillus helveticus ROO52 (10(9)cfu/d) for 21 days. Animal weight and food eaten were monitored weekly. Intestinal immune function was analysed for cytokine expression using the Meso Scale Discovery platform. Spatial memory and anxiety-like behavior was assessed in a Barnes maze. Terminal restriction fragment length polymorphism (TRFLP) was used to analyze the fecal microbiota. Both WT and IL-10(-/-) mice on a Western diet had increased weight gain along with changes in gut microbiota and cytokine expression and altered anxiety-like behavior. The ability of L. helveticus to modulate these factors was genotype- and diet-dependent. Anxiety-like behavior and memory were negatively affected by Western-style diet depending on inflammatory state, but this change was prevented with L. helveticus administration. However, probiotics alone decreased anxiety-like behavior in WT mice on a chow diet. Mice on the Western diet had decreased inflammation and fecal corticosterone, but these markers did not correlate with changes in behavior. Analysis of bacterial phyla from WT and IL-10(-/-)mice showed discrete clustering of the groups to be associated with both diet and probiotic supplementation, with the diet-induced shift normalized to some degree by L. helveticus. These findings suggest that the type of diet consumed by the host and the presence or absence of active inflammation may significantly alter the ability of probiotics to modulate host physiological function.

Early life exposure to sevoflurane impairs adulthood spatial memory in the rat

Sevoflurane is a general anesthetic commonly used in the pediatric setting because it is sweet-smelling, nonflammable, fast acting and has a very short recovery time. Although recent clinical data suggest that early anesthesia exposure is associated with subsequent learning and memory problems, it is difficult to determine the exact scope of developmental neurotoxicity associated with exposure to specific anesthetics such as sevoflurane. This is largely due to inconsistencies in the literature. Thus, in the present studies we evaluated the effect of early life exposure to sevoflurane (1%, 2%, 3% or 4%) on adulthood memory impairment in Sprague-Dawley rats. Animals were exposed to different regimens of sevoflurane anesthesia on postnatal days (PNDs) 3, 7, or 14 or at 7 weeks (P7W) of age and spatial memory performance was assessed in adulthood using the Morris Water Maze (MWM). Rats exposed to sevoflurane exhibited significant memory impairment which was concentration and exposure duration dependent. Disruption of MWM performance was more severe in animals exposed on both PNDs 3 and 7 than in animals exposed on both PNDs 3 and 14. The younger the animal's age at the time of exposure, the more significant the effect on later MWM performance. Compared to the neonates, animals exposed at P7W were relatively insensitive to sevoflurane: memory was impaired in this group only after repeated exposures to low doses or single exposures to high doses. Early life exposure to sevoflurane can result in spatial memory impairments in adulthood and the shorter the interval between exposures, the greater the deficit.

Comparison of the effects of the GABAB receptor positive modulator BHF177 and the GABAB receptor agonist baclofen on anxiety-like behavior, learning, and memory in mice

γ-Aminobutyric acid B (GABAB) receptor activation is a potential therapeutic approach for the treatment of drug addiction, pain, anxiety, and depression. However, full agonists of this receptor induce side-effects, such as sedation, muscle relaxation, tolerance, and cognitive disruption. Positive allosteric modulators (PAMs) of the GABAB receptor may have similar therapeutic effects as agonists with superior side-effect profiles. The present study behaviorally characterized N-([1R,2R,4S]-bicyclo[2.2.1]hept-2-yl)-2-methyl-5-(4-[trifluoromethyl]phenyl)-4-pyrimidinamine (BHF177), a GABAB receptor PAM, in mouse models of anxiety-like behavior, learning and memory. In addition, the effects of BHF177 were compared with the agonist baclofen. Unlike the anxiolytic chlordiazepoxide, baclofen (0.5, 1.5, and 2.5 mg/kg, intraperitoneally) and BHF177 (10, 20, and 40 mg/kg, orally) had no effect on anxiety-like behavior in the elevated plus maze, light/dark box, or Vogel conflict test. Baclofen increased punished drinking in the Vogel conflict test, but this effect may be attributable to the analgesic actions of baclofen. At the highest dose tested (2.5 mg/kg), baclofen-treated mice exhibited sedation-like effects (i.e., reduced locomotor activity) across many of the tests, whereas BHF177-treated mice exhibited no sedation-like effects. BHF177 exhibited pro-convulsion properties only in mice, but not in rats, indicating that this effect may be species-specific. At doses that were not sedative or pro-convulsant, baclofen and BHF177 had no selective effects on fear memory retrieval in contextual and cued fear conditioning or spatial learning and memory in the Barnes maze. These data suggest that BHF177 has little sedative activity, no anxiolytic-like profile, and minimal impairment of learning and memory in mice.

Enriched environment and masticatory activity rehabilitation recover spatial memory decline in aged mice

Background

To measure the impact of masticatory reduction on learning and memory, previous studies have produced experimental masticatory reduction by modified diet or molar removal. Here we induced spatial learning impairment in mice by reducing masticatory activity and then tested the effect of a combination of environmental enrichment and masticatory rehabilitation in recovering spatial learning at adulthood and in later life. For 6 months (6M) or 18 months (18M), we fed three groups of mice from postnatal day 21 respectively with a hard diet (HD) of pellets; pellets followed by a powdered, soft diet (HD/SD, divided into equal periods); or pellets followed by powder, followed by pellets again (HD/SD/HD, divided into equal periods). To mimic sedentary or active lifestyles, half of the animals from each group were raised from weaning in standard cages (impoverished environment; IE) and the other half in enriched cages (enriched environment; EE). To evaluate spatial learning, we used the Morris water maze.

Results

IE6M-HD/SD mice showed lower learning rates compared with control (IE6M-HD) or masticatory rehabilitated (IE6MHD/SD/HD) animals. Similarly, EE-HD/SD mice independent of age showed lower performance than controls (EE-HD) or rehabilitated mice (EE-HD/SD/HD). However, combined rehabilitation and EE in aged mice improved learning rate up to control levels. Learning rates did not correlate with swim speed.

Conclusions

Reduction in masticatory activity imposed on mice previously fed a hard diet (HD/SD) impaired spatial learning in the Morris water maze. In adults, masticatory rehabilitation recovered spatial abilities in both sedentary and active mice, and rehabilitation of masticatory activity combined with EE recovered these losses in aged mice.

Effects of fermented ginseng on memory impairment and β-amyloid reduction in Alzheimer's disease experimental models

This study examined the effect of fermented ginseng (FG) on memory impairment and β-amyloid (Aβ) reduction in models of Alzheimer’s disease (AD) in vitro and in vivo. FG extract was prepared by steaming and fermenting ginseng. In vitro assessment measured soluble Aβ42 levels in HeLa cells, which stably express the Swedish mutant form of amyloid precursor protein. After 8 h incubation with the FG extract, the level of soluble Aβ42 was reduced. For behavioral assessments, the passive avoidance test was used for the scopolamine-injected ICR mouse model, and the Morris water maze was used for a transgenic (TG) mouse model, which exhibits impaired memory function and increased Aβ42 level in the brain. FG extract was treated for 2 wk or 4 mo on ICR and TG mice, respectively. FG extract treatment resulted in a significant recovery of memory function in both animal models. Brain soluble Aβ42 levels measured from the cerebral cortex of TG mice were significantly reduced by the FG extract treatment. These findings extract was prepared by steaming and fermenting ginseng. of Aβ42 protein, which results in enhanced behavioral memory function, thus, suggesting that FG extract may be an effective preventive or treatment for AD.

Effects of diabetes on hippocampal neurogenesis: links to cognition and depression

Diabetes often leads to a number of complications involving brain function, including cognitive decline and depression. In addition, depression is a risk factor for developing diabetes. A loss of hippocampal neuroplasticity, which impairs the ability of the brain to adapt and reorganize key behavioral and emotional functions, provides a framework for understanding this reciprocal relationship. The effects of diabetes on brain and behavioral functions in experimental models of type 1 and type 2 diabetes are reviewed, with a focus on the negative impact of impaired hippocampal neurogenesis, dendritic remodeling and increased apoptosis. Mechanisms shown to regulate neuroplasticity and behavior in diabetes models, including stress hormones, neurotransmitters, neurotrophins, inflammation and aging, are integrated within this framework. Pathological changes in hippocampal function can contribute to the brain symptoms of diabetes-associated complications by failing to regulate the hypothalamic-pituitary-axis, maintain learning and memory and govern emotional expression. Further characterization of alterations in neuroplasticity along with glycemic control will facilitate the development and evaluation of pharmacological interventions that could successfully prevent and/or reverse the detrimental effects of diabetes on brain and behavior.