Exploratory activity, anxiety, and motor coordination in bigenic APPswe + PS1/ΔE9 mice

Chronic cannabidiol treatment improves social and object recognition in double transgenic APPswe/PS1∆E9 mice

RATIONALE

Patients suffering from Alzheimer's disease (AD) exhibit a decline in cognitive abilities including an inability to recognise familiar faces. Hallmark pathological changes in AD include the aggregation of amyloid-β (Aβ), tau protein hyperphosphorylation as well as pronounced neurodegeneration, neuroinflammation, neurotoxicity and oxidative damage.

OBJECTIVES

The non-psychoactive phytocannabinoid cannabidiol (CBD) exerts neuroprotective, anti-oxidant and anti-inflammatory effects and promotes neurogenesis. CBD also reverses Aβ-induced spatial memory deficits in rodents.

MATERIALS AND METHODS

Thus we determined the therapeutic-like effects of chronic CBD treatment (20 mg/kg, daily intraperitoneal injections for 3 weeks) on the APPswe/PS1∆E9 (APPxPS1) transgenic mouse model for AD in a number of cognitive tests, including the social preference test, the novel object recognition task and the fear conditioning paradigm. We also analysed the impact of CBD on anxiety behaviours in the elevated plus maze.

RESULTS

Vehicle-treated APPxPS1 mice demonstrated impairments in social recognition and novel object recognition compared to wild type-like mice. Chronic CBD treatment reversed these cognitive deficits in APPxPS1 mice without affecting anxiety-related behaviours.

CONCLUSIONS

This is the first study to investigate the effect of chronic CBD treatment on cognition in an AD transgenic mouse model. Our findings suggest that CBD may have therapeutic potential for specific cognitive impairments associated with AD.

Intravenous ascorbate improves spatial memory in middle-aged APP/PSEN1 and wild type mice

The present study investigated the effects of a single intravenous (i.v.) dose of Vitamin C (ascorbate, ASC) on spatial memory in APP/PSEN1 mice, an Alzheimer's disease model. First, we confirmed the uptake time course in ASC-depleted gulo (-/-) mice, which cannot synthesize ASC. Differential tissue uptake was seen based on ASC transporter distribution. Liver (SVCT1 and SVCT2) ASC was elevated at 30, 60 and 120 min post-treatment (125 mg/kg, i.v.), whereas spleen (SVCT2) ASC increased at 60 and 120 min. There was no detectable change in cortical (SVCT2 at choroid plexus, and neurons) ASC within the 2-h interval, although the cortex preferentially retained ASC. APP/PSEN1 and wild type (WT) mice at three ages (3, 9, or 20 months) were treated with ASC (125 mg/kg, i.v.) or saline 45 min before testing on the Modified Y-maze, a two-trial task of spatial memory. Memory declined with age and ASC treatment improved performance in 9-month-old APP/PSEN1 and WT mice. APP/PSEN1 mice displayed no behavioral impairment relative to WT controls. Although dopamine and metabolite DOPAC decreased in the nucleus accumbens with age, and improved spatial memory was correlated with increased dopamine in saline treated mice, acute ASC treatment did not alter monoamine levels in the nucleus accumbens. These data show that the Modified Y-maze is sensitive to age-related deficits, but not additional memory deficits due to amyloid pathology in APP/PSEN1 mice. They also suggest improvements in short-term spatial memory were not due to changes in the neuropathological features of AD or monoamine signaling.

Using mice to model Alzheimer's dementia: an overview of the clinical disease and the preclinical behavioral changes in 10 mouse models

The goal of this review is to discuss how behavioral tests in mice relate to the pathological and neuropsychological features seen in human Alzheimer's disease (AD), and present a comprehensive analysis of the temporal progression of behavioral impairments in commonly used AD mouse models that contain mutations in amyloid precursor protein (APP). We begin with a brief overview of the neuropathological changes seen in the AD brain and an outline of some of the clinical neuropsychological assessments used to measure cognitive deficits associated with the disease. This is followed by a critical assessment of behavioral tasks that are used in AD mice to model the cognitive changes seen in the human disease. Behavioral tests discussed include spatial memory tests [Morris water maze (MWM), radial arm water maze (RAWM), Barnes maze], associative learning tasks (passive avoidance, fear conditioning), alternation tasks (Y-Maze/T-Maze), recognition memory tasks (Novel Object Recognition), attentional tasks (3 and 5 choice serial reaction time), set-shifting tasks, and reversal learning tasks. We discuss the strengths and weaknesses of each of these behavioral tasks, and how they may correlate with clinical assessments in humans. Finally, the temporal progression of both cognitive and non-cognitive deficits in 10 AD mouse models (PDAPP, TG2576, APP23, TgCRND8, J20, APP/PS1, TG2576 + PS1 (M146L), APP/PS1 KI, 5×FAD, and 3×Tg-AD) are discussed in detail. Mouse models of AD and the behavioral tasks used in conjunction with those models are immensely important in contributing to our knowledge of disease progression and are a useful tool to study AD pathophysiology and the resulting cognitive deficits. However, investigators need to be aware of the potential weaknesses of the available preclinical models in terms of their ability to model cognitive changes observed in human AD. It is our hope that this review will assist investigators in selecting an appropriate mouse model, and accompanying behavioral paradigms to investigate different aspects of AD pathology and disease progression.

Effects of diphenyl diselenide on methylmercury toxicity in rats

This study investigates the efficacy of diphenyl diselenide [(PhSe)2] in attenuating methylmercury- (MeHg-)induced toxicity in rats. Adult rats were treated with MeHg [5 mg/kg/day, intragastrically (i.g.)] and/ or (PhSe)2 [1 mg/kg/day, intraperitoneally (i.p.)] for 21 days. Body weight gain and motor deficits were evaluated prior to treatment, on treatment days 11 and 21. In addition, hepatic and cerebral mitochondrial function (reactive oxygen species (ROS) formation, total and nonprotein thiol levels, membrane potential (ΔΨm), metabolic function, and swelling), hepatic, cerebral, and muscular mercury levels, and hepatic, cerebral, and renal thioredoxin reductase (TrxR) activity were evaluated. MeHg caused hepatic and cerebral mitochondrial dysfunction and inhibited TrxR activity in liver (38,9%), brain (64,3%), and kidney (73,8%). Cotreatment with (PhSe)2 protected hepatic and cerebral mitochondrial thiols from depletion by MeHg but failed to completely reverse MeHg's effect on hepatic and cerebral mitochondrial dysfunction or hepatic, cerebral, and renal inhibition of TrxR activity. Additionally, the cotreatment with (PhSe)2 increased Hg accumulation in the liver (50,5%) and brain (49,4%) and increased the MeHg-induced motor deficits and body-weight loss. In conclusion, these results indicate that (PhSe)2 can increase Hg body burden as well as the neurotoxic effects induced by MeHg exposure in rats.

Vitamin D2-enriched button mushroom (Agaricus bisporus) improves memory in both wild type and APPswe/PS1dE9 transgenic mice

Vitamin D deficiency is widespread, affecting over 30% of adult Australians, and increasing up to 80% for at-risk groups including the elderly (age>65). The role for Vitamin D in development of the central nervous system is supported by the association between Vitamin D deficiency and incidence of neurological and psychiatric disorders including Alzheimer's disease (AD). A reported positive relationship between Vitamin D status and cognitive performance suggests that restoring Vitamin D status might provide a cognitive benefit to those with Vitamin D deficiency. Mushrooms are a rich source of ergosterol, which can be converted to Vitamin D2 by treatment with UV light, presenting a new and convenient dietary source of Vitamin D2. We hypothesised that Vitamin D2-enriched mushrooms (VDM) could prevent the cognitive and pathological abnormalities associated with dementia. Two month old wild type (B6C3) and AD transgenic (APPSwe/PS1dE9) mice were fed a diet either deficient in Vitamin D2 or a diet which was supplemented with VDM, containing 1±0.2 µg/kg (∼54 IU/kg) vitamin D2, for 7 months. Effects of the dietary intervention on memory were assessed pre- and post-feeding. Brain sections were evaluated for amyloid β (Aβ) plaque loads and inflammation biomarkers using immuno-histochemical methods. Plasma vitamin D metabolites, Aβ40, Aβ42, calcium, protein and cholesterol were measured using biochemical assays. Compared with mice on the control diet, VDM-fed wild type and AD transgenic mice displayed improved learning and memory, had significantly reduced amyloid plaque load and glial fibrillary acidic protein, and elevated interleukin-10 in the brain. The results suggest that VDM might provide a dietary source of Vitamin D2 and other bioactives for preventing memory-impairment in dementia. This study supports the need for a randomised clinical trial to determine whether or not VDM consumption can benefit cognitive performance in the wider population.

Effects of specific multi-nutrient enriched diets on cerebral metabolism, cognition and neuropathology in AβPPswe-PS1dE9 mice

Recent studies have focused on the use of multi-nutrient dietary interventions in search of alternatives for the treatment and prevention of Alzheimer's disease (AD). In this study we investigated to which extent long-term consumption of two specific multi-nutrient diets can modulate AD-related etiopathogenic mechanisms and behavior in 11-12-month-old AβPPswe-PS1dE9 mice. Starting from 2 months of age, male AβPP-PS1 mice and wild-type littermates were fed either a control diet, the DHA+EPA+UMP (DEU) diet enriched with uridine monophosphate (UMP) and the omega-3 fatty acids docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), or the Fortasyn® Connect (FC) diet enriched with the DEU diet plus phospholipids, choline, folic acid, vitamins and antioxidants. We performed behavioral testing, proton magnetic resonance spectroscopy, immunohistochemistry, biochemical analyses and quantitative real-time PCR to gain a better understanding of the potential mechanisms by which these multi-nutrient diets exert protective properties against AD. Our results show that both diets were equally effective in changing brain fatty acid and cholesterol profiles. However, the diets differentially affected AD-related pathologies and behavioral measures, suggesting that the effectiveness of specific nutrients may depend on the dietary context in which they are provided. The FC diet was more effective than the DEU diet in counteracting neurodegenerative aspects of AD and enhancing processes involved in neuronal maintenance and repair. Both diets elevated interleukin-1β mRNA levels in AβPP-PS1 and wild-type mice. The FC diet additionally restored neurogenesis in AβPP-PS1 mice, decreased hippocampal levels of unbound choline-containing compounds in wild-type and AβPP-PS1 animals, suggesting diminished membrane turnover, and decreased anxiety-related behavior in the open field behavior. In conclusion, the current data indicate that specific multi-nutrient diets can influence AD-related etiopathogenic processes. Intervention with the FC diet might be of interest for several other neurodegenerative and neurological disorders.

APOE3, but not APOE4, bone marrow transplantation mitigates behavioral and pathological changes in a mouse model of Alzheimer disease

Apolipoprotein E4 (APOE4) genotype is the strongest genetic risk factor for late-onset Alzheimer disease and confers a proinflammatory, neurotoxic phenotype to microglia. Here, we tested the hypothesis that bone marrow cell APOE genotype modulates pathological progression in experimental Alzheimer disease. We performed bone marrow transplants (BMT) from green fluorescent protein-expressing human APOE3/3 or APOE4/4 donor mice into lethally irradiated 5-month-old APPswe/PS1ΔE9 mice. Eight months later, APOE4/4 BMT-recipient APPswe/PS1ΔE9 mice had significantly impaired spatial working memory and increased detergent-soluble and plaque Aβ compared with APOE3/3 BMT-recipient APPswe/PS1ΔE9 mice. BMT-derived microglia engraftment was significantly reduced in APOE4/4 recipients, who also had correspondingly less cerebral apoE. Gene expression analysis in cerebral cortex of APOE3/3 BMT recipients showed reduced expression of tumor necrosis factor-α and macrophage migration inhibitory factor (both neurotoxic cytokines) and elevated immunomodulatory IL-10 expression in APOE3/3 recipients compared with those that received APOE4/4 bone marrow. This was not due to detectable APOE-specific differences in expression of microglial major histocompatibility complex class II, C-C chemokine receptor (CCR) type 1, CCR2, CX3C chemokine receptor 1 (CX3CR1), or C5a anaphylatoxin chemotactic receptor (C5aR). Together, these findings suggest that BMT-derived APOE3-expressing cells are superior to those that express APOE4 in their ability to mitigate the behavioral and neuropathological changes in experimental Alzheimer disease.

Comprehensive behavioral characterization of an APP/PS-1 double knock-in mouse model of Alzheimer's disease

INTRODUCTION

Despite the extensive mechanistic and pathological characterization of the amyloid precursor protein (APP)/presenilin-1 (PS-1) knock-in mouse model of Alzheimer's disease (AD), very little is known about the AD-relevant behavioral deficits in this model. Characterization of the baseline behavioral performance in a variety of functional tasks and identification of the temporal onset of behavioral impairments are important to provide a foundation for future preclinical testing of AD therapeutics. Here we perform a comprehensive behavioral characterization of this model, discuss how the observed behavior correlates with the mechanistic and pathological observations of others, and compare this model with other commonly used AD mouse models.

METHODS

FOUR DIFFERENT GROUPS OF MICE RANGING ACROSS THE LIFESPAN OF THIS MODEL (TEST GROUPS: 7, 11, 15, and 24 months old) were run in a behavioral test battery consisting of tasks to assess motor function (grip strength, rotor rod, beam walk, open field ambulatory movement), anxiety-related behavior (open field time spent in peripheral zone vs. center zone, elevated plus maze), and cognitive function (novel object recognition, radial arm water maze).

RESULTS

There were no differences in motor function or anxiety-related behavior between APP/PS-1 knock-in mice and wild-type counterpart mice for any age group. Cognitive deficits in both recognition memory (novel object recognition) and spatial reference memory (radial arm water maze) became apparent for the knock-in animals as the disease progressed.

CONCLUSION

This is the first reported comprehensive behavioral analysis of the APP/PS1 knock-in mouse model of AD. The lack of motor/coordination deficits or abnormal anxiety levels, coupled with the age/disease-related cognitive decline and high physiological relevance of this model, make it well suited for utilization in preclinical testing of AD-relevant therapeutics.

A longitudinal study of cognition, proton MR spectroscopy and synaptic and neuronal pathology in aging wild-type and AβPPswe-PS1dE9 mice

Proton magnetic resonance spectroscopy (¹H MRS) is a valuable tool in Alzheimer’s disease research, investigating the functional integrity of the brain. The present longitudinal study set out to characterize the neurochemical profile of the hippocampus, measured by single voxel ¹H MRS at 7 Tesla, in the brains of AβPPSswe-PS1dE9 and wild-type mice at 8 and 12 months of age. Furthermore, we wanted to determine whether alterations in hippocampal metabolite levels coincided with behavioral changes, cognitive decline and neuropathological features, to gain a better understanding of the underlying neurodegenerative processes. Moreover, correlation analyses were performed in the 12-month-old AβPP-PS1 animals with the hippocampal amyloid-β deposition, TBS-T soluble Aβ levels and high-molecular weight Aβ aggregate levels to gain a better understanding of the possible involvement of Aβ in neurochemical and behavioral changes, cognitive decline and neuropathological features in AβPP-PS1 transgenic mice. Our results show that at 8 months of age AβPPswe-PS1dE9 mice display behavioral and cognitive changes compared to age-matched wild-type mice, as determined in the open field and the (reverse) Morris water maze. However, there were no variations in hippocampal metabolite levels at this age. AβPP-PS1 mice at 12 months of age display more severe behavioral and cognitive impairment, which coincided with alterations in hippocampal metabolite levels that suggest reduced neuronal integrity. Furthermore, correlation analyses suggest a possible role of Aβ in inflammatory processes, synaptic dysfunction and impaired neurogenesis.

The neurotrophic compound J147 reverses cognitive impairment in aged Alzheimer's disease mice

Introduction

Despite years of research, there are no disease-modifying drugs for Alzheimer's disease (AD), a fatal, age-related neurodegenerative disorder. Screening for potential therapeutics in rodent models of AD has generally relied on testing compounds before pathology is present, thereby modeling disease prevention rather than disease modification. Furthermore, this approach to screening does not reflect the clinical presentation of AD patients which could explain the failure to translate compounds identified as beneficial in animal models to disease modifying compounds in clinical trials. Clearly a better approach to pre-clinical drug screening for AD is required.

Methods

To more accurately reflect the clinical setting, we used an alternative screening strategy involving the treatment of AD mice at a stage in the disease when pathology is already advanced. Aged (20-month-old) transgenic AD mice (APP/swePS1ΔE9) were fed an exceptionally potent, orally active, memory enhancing and neurotrophic molecule called J147. Cognitive behavioral assays, histology, ELISA and Western blotting were used to assay the effect of J147 on memory, amyloid metabolism and neuroprotective pathways. J147 was also investigated in a scopolamine-induced model of memory impairment in C57Bl/6J mice and compared to donepezil. Details on the pharmacology and safety of J147 are also included.

Results

Data presented here demonstrate that J147 has the ability to rescue cognitive deficits when administered at a late stage in the disease. The ability of J147 to improve memory in aged AD mice is correlated with its induction of the neurotrophic factors NGF (nerve growth factor) and BDNF (brain derived neurotrophic factor) as well as several BDNF-responsive proteins which are important for learning and memory. The comparison between J147 and donepezil in the scopolamine model showed that while both compounds were comparable at rescuing short term memory, J147 was superior at rescuing spatial memory and a combination of the two worked best for contextual and cued memory.

Conclusion

J147 is an exciting new compound that is extremely potent, safe in animal studies and orally active. J147 is a potential AD therapeutic due to its ability to provide immediate cognition benefits, and it also has the potential to halt and perhaps reverse disease progression in symptomatic animals as demonstrated in these studies.

Sex-dependent behavioral functions of the Purkinje cell-specific Gαi/o binding protein, Pcp2(L7)

We previously reported motor and non-motor enhancements in a mouse mutant with an inactivated Purkinje cell-specific gene, Pcp2(L7), that encodes a GoLoco domain-containing modulator of Gi/o protein-coupled receptors. Effects included elevated learning asymptote with repeated rotarod training, increased acquisition rate in tone-cued fear conditioning (FC), and subtle male-specific changes in both acoustic startle habituation and pre-pulse inhibition. We have further analyzed this mutant strain this time with a focus on male-female differences, and here we report a sex-dependent anxiety-like phenotype: male mutants are less anxious, and female mutants are more anxious, than same-sex wild types. Similarly, the fear responses measured during the tone in FC acquisition are decreased in male mutants and increased in female mutants relative to same-sex wild types. Overall, the dynamics of both acquisition and extinction of FC is affected in mutants but memory was not affected. In the social realm, compositional analysis of sociability and preference for social novelty data supports that both L7 genotype and sex contribute to these behaviors. These results provide direct evidence of emotional functions of the cerebellum due to the unambiguous cerebellar specificity of Pcp2(L7) expression and the lack of any confounding motor defects in the mutant. We attempt to synthesize these new data with what is previously known both about Pcp2(L7) and about the effects of sex and sex hormones on anxiety and fear behaviors: specifically, L7 is a bidirectional and sex-dependent damper that regulates the amplitude and/or rate of sensorimotor responses, potentially acting as a mood stabilizer.

Novel behavioural characteristics of the APP(Swe)/PS1ΔE9 transgenic mouse model of Alzheimer's disease

In order to better understand animal models of Alzheimer's disease, novel phenotyping strategies have been established for transgenic mouse models. In line with this, the current study characterised male APPxPS1 transgenic mice on mixed C57BL/6JxC3H/HeJ background for the first time for social recognition memory, sensorimotor gating, and spatial memory using the cheeseboard test as an alternative to the Morris water maze. Furthermore, locomotion, anxiety, and fear conditioning were evaluated in transgenic and wild type-like animals. APPxPS1 males displayed task-dependent hyperlocomotion and anxiety behaviours and exhibited social recognition memory impairments compared to wild type-like littermates. Spatial learning and memory, fear conditioning, and sensorimotor gating were unaffected in APPxPS1 transgenic mice. In conclusion, this study describes for the first time social recognition memory deficits in male APPxPS1 mice and suggests that spatial learning and memory deficits reported in earlier studies are dependent on the sex and genetic background of the APPxPS1 mouse line used. Furthermore, particular test conditions of anxiety and spatial memory paradigms appear to impact on the behavioural response of this transgenic mouse model for Alzheimer's disease.

Longitudinal behavioral changes in the APP/PS1 transgenic Alzheimer's disease model

The APP/PS1 double transgenic mouse is an Alzheimer's Disease-like model. However, cognitive deficits measured at one age do not necessarily indicate age-related progressions. Further, results of the most widely used behavioral assessment, water maze performance, are generally limited to 1-2 endpoints. Here, male APP/PS1 and noncarrier wildtypes (n=11/group) were assessed at 7-15 months of age for water maze, open field, and motor coordination performance. Body weights and motor coordination were comparable for both groups throughout. Beginning at approximately 9 months of age, the transgenic group exhibited hypoactivity in the open field which continued throughout. Latency to locate the platform and swim path length were longer in the transgenic group; however, these appeared to be more related to increased floating and thigmotactic behavior and only partially related to a cognitive impairment. Age-related decrements in performance were not substantial; however, substantial plaque numbers were measured in six representative 16-month-old transgenic mice. The stability of water maze performance may be related to the longitudinal testing and repetitive experience, which previous research has demonstrated can confer beneficial effects on behavior and plaque deposition in transgenic Alzheimer's Disease models [1]. These results emphasize the importance of measuring multiple water maze endpoints and demonstrate the feasibility of longitudinal assessments in this model.

Neurologic and motor dysfunctions in APP transgenic mice

The discovery of gene mutations underlying autosomal dominant Alzheimer's disease has enabled researchers to reproduce several hallmarks of this disorder in transgenic mice, notably the formation of Aβ plaques in brain and cognitive deficits. APP transgenic mutants have also been investigated with respect to survival rates, neurologic functions, and motor coordination, which are all susceptible to alteration in Alzheimer dementia. Several transgenic lines expressing human mutated or wild-type APP had higher mortality rates than non-transgenic controls with or without the presence of Aβ plaques. Mortality rates were also elevated in APP transgenic mice with vascular amyloid accumulation, thereby implicating cerebrovascular factors in the precocious death observed in all APP transgenic models. In addition, myoclonic jumping has been described in APP mutants, together with seizure activity, abnormal limb-flexion and paw-clasping reflexes, and motor coordination deficits. The neurologic signs resemble the myoclonic movements, epileptic seizures, pathological reflexes, and gait problems observed in late-stage Alzheimer's disease.

[Effects of physical exercise on cognitive alterations and oxidative stress in an APP/PSN1 transgenic model of Alzheimer's disease]

INTRODUCTION

The beneficial effects of physical exercise, in both the treatment and the prevention of several diseases, have been extensively demonstrated. The most common dementia, Alzheimer's disease (AD), is a disorder in which exercise induces significant improvement at pathophysiopathological and cognitive levels. In the present work, we studied the relationship between physical exercise, oxidative stress, and cognition in the double transgenic mice model (2×Tg) for AD, APP/PSN1. This model is mainly based on the cerebral deposition of amyloid β plaques.

MATERIAL AND METHODS

Eighteen ten-month-old mice were divided into four experimental groups: exercised 2×Tg (2×Tg-E) (n=5), rested 2×Tg (2×Tg-R) (n=5), exercised controls (control-E) (n=4) and rested controls (control-R) (n=4). We trained the animals for twelve weeks with a combination of forced exercise (treadmill running three days/week) and spontaneous wheel running. The animals were evaluated with physical and cognitive tests before and after the training period. We analyzed systemic and cortical oxidative damage and the induction of antioxidant enzymes.

RESULTS

The 2×Tg-R mice showed a decrease in their grip strength and VO(2max) as they grew older which was prevented by training. The 2×Tg-E group showed better memory than the 2×Tg-R animals. All the trained groups demonstrated greater exploratory capacity and less anxiety than the sedentary animals. Systemic oxidative damage was slightly decreased in the 2×Tg, although we found no difference in the lipoperoxidation and in the induction of the antioxidant defense in cortex between groups.

CONCLUSIONS

Physical exercise leads to improvements in the grip strength, VO(2max), cognition, and memory in 2×Tg mice. These improvements are not significantly related to changes in the antioxidant defenses or a reduction in the oxidative damage brought about by exercise.

Brain regions and genes affecting myoclonus in animals

Myoclonus is defined as large-amplitude rhythmic movements. Brain regions underlying myoclonic jerks include brainstem, cerebellum, and cortex. Gamma-aminobutyric acid (GABA) appears to be the main neurotransmitter involved in myoclonus, possibly interacting with biogenic amines, opiates, acetylcholine, and glycine. Myoclonic jumping is a specific subtype seen in rodents, comprising rearing and hopping continuously against a wall. Myoclonic jumping can be seen in normal mouse strains, possibly as a result of simply being put inside a cage. Like other types, it is also triggered by changes in GABA, 5HT, and dopamine neurotransmission. Implicated brain regions include hippocampus and dorsal striatum, possibly with respect to D(1) dopamine, NMDA, and δ opioid receptors. There is reason to suspect that myoclonic jumping is underreported due to insufficient observations into mouse cages.

APP transgenic mice for modelling behavioural and psychological symptoms of dementia (BPSD)

The discovery of gene mutations responsible for autosomal dominant Alzheimer's disease has enabled researchers to reproduce in transgenic mice several hallmarks of this disorder, notably Aβ accumulation, though in most cases without neurofibrillary tangles. Mice expressing mutated and wild-type APP as well as C-terminal fragments of APP exhibit variations in exploratory activity reminiscent of behavioural and psychological symptoms of Alzheimer dementia (BPSD). In particular, open-field, spontaneous alternation, and elevated plus-maze tasks as well as aggression are modified in several APP transgenic mice relative to non-transgenic controls. However, depending on the precise murine models, changes in open-field and elevated plus-maze exploration occur in either direction, either increased or decreased relative to controls. It remains to be determined which neurotransmitter changes are responsible for this variability, in particular with respect to GABA, 5HT, and dopamine.

Developmental nicotine exposure induced alterations in behavior and glutamate receptor function in hippocampus

In the developing brain, nicotinic acetylcholine receptors (nAChRs) are involved in cell survival, targeting, formation of neural and sensory circuits, and development and maturation of other neurotransmitter systems. This regulatory role is disrupted when the developing brain is exposed to nicotine, which occurs with tobacco use during pregnancy. Prenatal nicotine exposure has been shown to be a strong risk factor for memory deficits and other behavioral aberrations in the offspring. The molecular mechanisms underlying these neurobehavioral outcomes are not clearly elucidated. We used a rodent model to assess behavioral, neurophysiological, and neurochemical consequences of prenatal nicotine exposure in rat offspring with specific emphasis on the hippocampal glutamatergic system. Pregnant dams were infused with nicotine (6 mg/kg/day) subcutaneously from the third day of pregnancy until birth. Results indicate that prenatal nicotine exposure leads to increased anxiety and depressive-like effects and impaired spatial memory. Synaptic plasticity in the form of long-term potentiation (LTP), basal synaptic transmission, and AMPA receptor-mediated synaptic currents were reduced. The deficit in synaptic plasticity was paralleled by declines in protein levels of vesicular glutamate transporter 1 (VGLUT1), synaptophysin, AMPA receptor subunit GluR1, phospho(Ser845) GluR1, and postsynaptic density 95 (PSD-95). These results suggest that prenatal nicotine exposure by maternal smoking could result in alterations in the glutamatergic system in the hippocampus contributing to the abnormal neurobehavioral outcomes.

The effects of MyD88 deficiency on exploratory activity, anxiety, motor coordination, and spatial learning in C57BL/6 and APPswe/PS1dE9 mice

Toll-like receptors (TLRs) are a family of pattern-recognition receptors in innate immunity and provide a first line defense against pathogens and tissue injuries. In addition to important roles in infection, inflammation, and immune diseases, recent studies show that TLR signaling is involved in modulation of learning, memory, mood, and neurogenesis. Because MyD88 is essential for the downstream signaling of all TLRs, except TLR3, we investigated the effects of MyD88 deficiency (MyD88-/-) on behavioral functions in mice. Additionally, we recently demonstrated that a mouse model of Alzheimer's disease (AD) deficient for MyD88 had decreases in Aβ deposits and soluble Aβ in the brain as compared with MyD88 sufficient AD mouse models. Because accumulation of Aβ in the brain is postulated to be a causal event leading to cognitive deficits in AD, we investigated the effects of MyD88 deficiency on behavioral functions in the AD mouse model at 10 months of age. MyD88 deficient mice showed more anxiety in the elevated plus-maze. In the motor coordination tests, MyD88 deficient mice remained on a beam and a bar for a longer time, but with slower initial movement on the bar. In the Morris water maze test, MyD88 deficiency appeared to improve spatial learning irrespective of the transgene. Our findings suggest that the MyD88-dependent pathway contributes to behavioral functions in an AD mouse model and its control group.

TLR4 mutation reduces microglial activation, increases Aβ deposits and exacerbates cognitive deficits in a mouse model of Alzheimer's disease

BACKGROUND

Amyloid plaques, a pathological hallmark of Alzheimer's disease (AD), are accompanied by activated microglia. The role of activated microglia in the pathogenesis of AD remains controversial: either clearing Aβ deposits by phagocytosis or releasing proinflammatory cytokines and cytotoxic substances. Microglia can be activated via toll-like receptors (TLRs), a class of pattern-recognition receptors in the innate immune system. We previously demonstrated that an AD mouse model homozygous for a loss-of-function mutation of TLR4 had increases in Aβ deposits and buffer-soluble Aβ in the brain as compared with a TLR4 wild-type AD mouse model at 14-16 months of age. However, it is unknown if TLR4 signaling is involved in initiation of Aβ deposition as well as activation and recruitment of microglia at the early stage of AD. Here, we investigated the role of TLR4 signaling and microglial activation in early stages using 5-month-old AD mouse models when Aβ deposits start.

METHODS

Microglial activation and amyloid deposition in the brain were determined by immunohistochemistry in the AD models. Levels of cerebral soluble Aβ were determined by ELISA. mRNA levels of cytokines and chemokines in the brain and Aβ-stimulated monocytes were quantified by real-time PCR. Cognitive functions were assessed by the Morris water maze.

RESULTS

While no difference was found in cerebral Aβ load between AD mouse models at 5 months with and without TLR4 mutation, microglial activation in a TLR4 mutant AD model (TLR4M Tg) was less than that in a TLR4 wild-type AD model (TLR4W Tg). At 9 months, TLR4M Tg mice had increased Aβ deposition and soluble Aβ42 in the brain, which were associated with decrements in cognitive functions and expression levels of IL-1β, CCL3, and CCL4 in the hippocampus compared to TLR4W Tg mice. TLR4 mutation diminished Aβ-induced IL-1β, CCL3, and CCL4 expression in monocytes.

CONCLUSION

This is the first demonstration of TLR4-dependent activation of microglia at the early stage of β-amyloidosis. Our results indicate that TLR4 is not involved in the initiation of Aβ deposition and that, as Aβ deposits start, microglia are activated via TLR4 signaling to reduce Aβ deposits and preserve cognitive functions from Aβ-mediated neurotoxicity.

Effect of chronic hCG administration on Alzheimer's-related cognition and A beta accumulation in PS1KI mice

Age-associated changes in the reproductive hormones-the gonadal steroid hormones and the gonadotropins-have been identified as potential risk factors for Alzheimer's disease (AD). However, levels of gonadotropins and estrogens are closely linked in vivo, and it has proven difficult to separate the effects of gonadotropins from the well-documented estrogenic effects on AD-related neuropathology in experimental models of menopause. To assess the effects of gonadotropins on cognition and AD biochemical markers independent of estrogenic effects, a potent analog of luteinizing hormone [human chorionic gonadotropin (hCG)] was administered to ovariectomized presenilin1 knock-in mice (PS1KI). Gonadotropin administration was found to induce hyperactivity and anxiety (Open Field Maze and Taste Neophobia Task) and working memory dysfunction, without altering reference memory (Morris Water Maze). Although gonadotropin administration modestly altered β amyloid (Aβ40) levels, levels of the longer more toxic form (Aβ42) were unaffected. Furthermore, altered Aβ40 levels were not associated with observed behavioral and cognitive impairments. These findings provide proof, in principle, that the gonadotropin hormones play a role in the modulation of AD-related behavior, cognition, and neuropathology.

Enoxaparin treatment administered at both early and late stages of amyloid β deposition improves cognition of APPswe/PS1dE9 mice with differential effects on brain Aβ levels

Enoxaparin (Enox), a low molecular weight heparin, has been shown to lower brain amyloid beta (A beta) load in a mouse model for Alzheimer's disease. However, the effect of Enox on cognition was not studied. Therefore, we examined the effect of peripheral Enox treatment on cognition and brain A beta levels in the APPswe/PS1dE9 mouse model by giving injections at an early (starting at 5 months of age) and late (starting at 10 and 12 months of age) stage of A beta accumulation for 3 months. Although Enox had no effect on behaviour in the open field at any age, it improved spatial memory in the Morris water maze in 5-, 10- and 12-month-old mice. Furthermore, Enox treatment seemed to decrease guanidine HCl-extracted brain A beta levels at 5 months of age, but significantly increased guanidine HCl-extracted A beta 42 and A beta 40 levels in both 10- and 12-month-old mice. In vitro, Enox increased aggregation of A beta, even when A beta was pre-aggregated. In conclusion, Enox treatment, either at an early or a late stage of A beta accumulation, could improve cognition in APPswe/PS1dE9 mice. However, since Enox treatment at an early stage of A beta accumulation decreased guanidine HCl-extracted A beta levels and Enox treatment at a late stage enhanced guanidine HCl-extracted A beta levels, it seems that Enox influences A beta deposition differently at different stages of A beta pathology. In any case, our study suggests that enoxaparin treatment has potential as a therapeutic agent for Alzheimer's disease.

The effect of encapsulated VEGF-secreting cells on brain amyloid load and behavioral impairment in a mouse model of Alzheimer's disease

Cerebrovascular dysfunction contributes to cognitive decline and neurodegeneration in Alzheimer's disease (AD). Vascular endothelial growth factor (VEGF), an angiogenic protein with important neurotrophic and neuroprotective actions, is under investigation as a therapeutic agent for the treatment of neurodegenerative disorders. The aim of this study was to generate encapsulated VEGF-secreting cells and implant them in a transgenic mouse model of AD, the double mutant amyloid precursor protein/presenilin 1 (APP/Ps1) mice, which shows a disturbed vessel homeostasis. We report that, after implantation of VEGF microcapsules, brain Abeta burden, hyperphosphorylated-tau and cognitive impairment attenuated in APP/Ps1 mice. Based on the neurovascular hypothesis, our findings suggest a new potential therapeutic approach that could be developed for AD, to enhance Abeta clearance and neurovascular repair, and to protect the cognitive behavior. Stereologically-implanted encapsulated VEGF-secreting cells could offer an alternative strategy in the treatment of AD.

Induced LC degeneration in APP/PS1 transgenic mice accelerates early cerebral amyloidosis and cognitive deficits

Degeneration of locus ceruleus neurons and subsequent reduction of norepinephrine concentration in locus ceruleus projection areas represent an early pathological indicator of Alzheimer's disease. In order to model the pathology of the human disease and to study the effects of norepinephrine-depletion on amyloid precursor protein processing, behaviour, and neuroinflammation, locus ceruleus degeneration was induced in mice coexpressing the swedish mutant of the amyloid precursor protein and the presenilin 1 DeltaExon 9 mutant (APP/PS1) using the neurotoxin N-(2-chloroethyl)-N-ethyl-bromo-benzylamine (dsp4) starting treatment at 3 months of age. Norepinephrine transporter immunolabelling demonstrated severe loss of locus ceruleus neurons and loss of cortical norepinephrine transporter starting as early as 4.5 months of age and aggravating over time. Of note, dsp4-treated transgenic mice showed elevated amyloid beta levels and impaired spatial memory performance at 6.5 months of age compared to control-treated APP/PS1 transgenic mice, indicating an accelerating effect on cerebral amyloidosis and cognitive deficits. Likewise, norepinephrine-depletion increased neuroinflammation compared to transgenic controls as verified by macrophage inflammatory protein-1alpha and -1beta gene expression analysis. Exploratory activity and memory retention was compromised by age in APP/PS1 transgenic mice and further aggravated by induced noradrenergic deficiency. In contrast, novel object recognition was not influenced by norepinephrine deficiency, but by the APP/PS1 transgene at 12 months. Overall, our data indicate that early loss of noradrenergic innervation promotes amyloid deposition and modulates the activation state of inflammatory cells. This in turn could have had impact on the acceleration of cognitive deficits observed over time.

Vitamin C deficiency increases basal exploratory activity but decreases scopolamine-induced activity in APP/PSEN1 transgenic mice

Vitamin C is a powerful antioxidant and its levels are decreased in Alzheimer's patients. Even sub-clinical vitamin C deficiency could impact disease development. To investigate this principle we crossed APP/PSEN1 transgenic mice with Gulo knockout mice unable to synthesize their own vitamin C. Experimental mice were maintained from 6 weeks of age on standard (0.33 g/L) or reduced (0.099 g/L) levels of vitamin C and then assessed for changes in behavior and neuropathology. APP/PSEN1 mice showed impaired spatial learning in the Barnes maze and water maze that was not further impacted by vitamin C level. However, long-term decreased vitamin C levels led to hyperactivity in transgenic mice, with altered locomotor habituation and increased omission errors in the Barnes maze. Decreased vitamin C also led to increased oxidative stress. Transgenic mice were more susceptible to the activity-enhancing effects of scopolamine and low vitamin C attenuated these effects in both genotypes. These data indicate an interaction between the cholinergic system and vitamin C that could be important given the cholinergic degeneration associated with Alzheimer's disease.

Progesterone reduces depression-like behavior in a murine model of Alzheimer's Disease

Although anxiety and depression are not the core symptoms of Alzheimer's Disease (AD), there are changes observed in mood in those with AD, as well as in the aging population. Anxiety and depression may be influenced by progesterone P(4) and/or its neuroactive metabolites, dihydroprogesterone (DHP) and 5 alpha-pregnan-3 alpha-ol-20-one (3 alpha,5 alpha-THP). To begin to investigate progestogens' role in AD, a double transgenic mouse model of early-onset familial AD that co-overexpresses mutant forms of amyloid precursor protein (APPswe) and presenilin 1 Delta exon 9 mutation was utilized. As such, the effects of long-term (from 6 to 12 months of age) administration of P(4) to ovariectomized (ovx) wildtype and APPswe+PSEN1 Delta e9 mice for changes in affective behavior was investigated. APPswe+PSEN1 Delta 9 mutant mice had increased anxiety-like (i.e., increased emergence latencies, decreased time spent on the open quadrants of the elevated zero maze) and increased depressive-like behavior (i.e., increased time spent immobile) than did wildtype mice. Compared to vehicle-administration, P(4) administration (which produced physiological circulating P(4), DHP, and 3 alpha,5 alpha-THP levels, particularly in the wildtype mice) decreased depressant-like behavior in the forced swim test. These effects occurred independent of changes in general motor behavior/coordination, pain threshold, and plasma corticosterone levels. Thus, the APPswe+PSEN1 Delta 9 mutation alters affective behavior, and P(4) treatment reversed depressive-like behavior.

Ameliorative effects of yokukansan, a traditional Japanese medicine, on learning and non-cognitive disturbances in the Tg2576 mouse model of Alzheimer's disease

AIM OF THIS STUDY

Aim of the present study is to clarify the effects of yokukansan (TJ-54) on learning and non-cognitive disturbances in the Tg2576 mouse expressing the human form of the APP695SWE (APP-Tg mice), which is considered to be an animal model of Alzheimer's disease.

MATERIALS AND METHODS

Powdered diets containing 0.5 and 1.0% TJ-54 were given to the mice for 10 months (from 5 to 15 months old). The Morris water-maze test, elevated plus-maze test, and open-field test were performed for evaluation of learning and non-cognitive disturbances.

RESULTS

Treatment with 1.0% TJ-54 for 5 months shortened the time it took for APP-Tg positive (+) mice to reach the platform in the Morris water-maze test. In the elevated plus-maze test, treatment with 1.0% TJ-54 for 2 months significantly reduced the increased number of entries and the time spent in open arms observed in APP-Tg(+) mice. In an open-field test, treatment of 1.0% TJ-54 for 9 months significantly suppressed the increase in locomotion observed in APP-Tg(+) mice.

CONCLUSION

These results suggest the possibility that TJ-54 ameliorates learning deficits and non-cognitive defects including a decrease in the anxiety (or disinhibition) and an increase in locomotor activity (hyperactivity) observed in APP-Tg(+) mice.

DHA and cholesterol containing diets influence Alzheimer-like pathology, cognition and cerebral vasculature in APPswe/PS1dE9 mice

Cholesterol and docosahexenoic acid (DHA) may affect degenerative processes in Alzheimer's Disease (AD) by influencing Abeta metabolism indirectly via the vasculature. We investigated whether DHA-enriched diets or cholesterol-containing Typical Western Diets (TWD) alter behavior and cognition, cerebral hemodynamics (relative cerebral blood volume (rCBV)) and Abeta deposition in 8- and 15-month-old APP(swe)/PS1(dE9) mice. In addition we investigated whether changes in rCBV precede changes in Abeta deposition or vice versa. Mice were fed regular rodent chow, a TWD-, or a DHA-containing diet. Behavior, learning and memory were investigated, and rCBV was measured using contrast-enhanced MRI. The Abeta load was visualized immunohistochemically. We demonstrate that DHA altered rCBV in 8-month-old APP/PS1 and wild type mice[AU1]. In 15-month-old APP/PS1 mice DHA supplementation improved spatial memory, decreased Abeta deposition and slightly increased rCBV, indicating that a DHA-enriched diet can diminish AD-like pathology. In contrast, TWD diets decreased rCBV in 15-month-old mice. The present data indicate that long-term dietary interventions change AD-like pathology in APP/PS1 mice. Additionally, effects of the tested diets on vascular parameters were observed before effects on Abeta load were noted. These data underline the importance of vascular factors in the APP/PS1 mouse model of AD pathology.

Episodic memory deficits are not related to altered glutamatergic synaptic transmission and plasticity in the CA1 hippocampus of the APPswe/PS1δE9-deleted transgenic mice model of ß-amyloidosis

Alzheimer's disease (AD) is characterized by progressive memory impairment and the formation of amyloid plaques in the brain. Dysfunctional excitatory synaptic transmission and synaptic plasticity are generally accepted as primary events in the development of AD, and beta-amyloid is intimately involved. Here we describe age related differences in learning, memory, synaptic transmission and long-term potentiation (LTP) in wild type and APPswe/PS1DeltaE9 mice, which produce increasing amounts of Abeta1-42 with age. The mice have both age related and age-independent deficits in radial arm water maze performance. Blind studies of hippocampal slices from transgenic and wild type mice demonstrate that transgenic mice have impaired transient LTP and that the degree of impairment is not related to age from 3 to 12 months. The deficiencies in transient LTP may be related to the behavioral deficits that did not progress with age. The accumulation of beta-amyloid and the episodic memory deficits, both of which increased with age, were not accompanied by an alteration in synaptic transmission or sustained LTP in the in vitro hippocampal slices.

Deficits in working memory and motor performance in the APP/PS1ki mouse model for Alzheimer's disease

The APP/PS1ki mouse model for Alzheimer's disease (AD) exhibits robust brain and spinal cord axonal degeneration and hippocampal CA1 neuron loss starting at 6 months of age. It expresses human mutant APP751 with the Swedish and London mutations together with two FAD-linked knocked-in mutations (PS1 M233T and PS1 L235P) in the murine PS1 gene. The present report covers a phenotypical analysis of this model using either behavioral tests for working memory and motor performance, as well as an analysis of weight development and body shape. At the age of 6 months, a dramatic, age-dependent change in all of these properties and characteristics was observed, accompanied by a significantly reduced ability to perform working memory and motor tasks. The APP/PS1ki mice were smaller and showed development of a thoracolumbar kyphosis, together with an incremental loss of body weight. While 2-month-old APP/PS1ki mice were inconspicuous in all of these tasks and properties, there is a massive age-related impairment in all tested behavioral paradigms. We have previously reported robust axonal degeneration in brain and spinal cord, as well as abundant hippocampal CA1 neuron loss starting at 6 months of age in the APP/PS1ki mouse model, which coincides with the onset of motor and memory deficits described in the present report.

Review on the APP/PS1KI mouse model: intraneuronal Abeta accumulation triggers axonopathy, neuron loss and working memory impairment

Accumulating evidence points to an important role of intraneuronal Abeta as a trigger of the pathological cascade of events leading to neurodegeneration and eventually to Alzheimer's disease (AD) with its typical clinical symptoms, like memory impairment and change in personality. As a new concept, intraneuronal accumulation of Abeta instead of extracellular Abeta deposition has been introduced to be the disease-triggering event in AD. The present review compiles current knowledge on the amyloid precursor protein (APP)/PS1KI mouse model with early and massive intraneuronal Abeta42 accumulation: (1) The APP/PS1KI mouse model exhibits early robust brain and spinal cord axonal degeneration and hippocampal CA1 neuron loss. (2) At the same time-point, a dramatic, age-dependent reduced ability to perform working memory and motor tasks is observed. (3) The APP/PS1KI mice are smaller and show development of a thoracolumbar kyphosis, together with an incremental loss of body weight. (4) Onset of the observed behavioral alterations correlates well with robust axonal degeneration in brain and spinal cord and with abundant hippocampal CA1 neuron loss.

Motor impairment in Alzheimer's disease and transgenic Alzheimer's disease mouse models

In this commentary, we accent the accumulating evidence for motor impairment as a common feature of early Alzheimer's disease (AD) pathology. In addition, we summarize the state of knowledge on this phenotype in experimental mouse models, expressing AD-associated genes like tau or amyloid precursor protein.

One-year longitudinal evaluation of sensorimotor functions in APP751SL transgenic mice

Intracerebral amyloid-beta (Abeta) peptide deposition is considered to play a key role in Alzheimer's disease and is designated as a principal therapeutic target. The relationship between brain Abeta levels and clinical deficits remains, however, unclear, both in human patients and in animal models of the disease. The purpose of the present study was to investigate, in a transgenic mouse model of brain amyloidosis, the consequences of Abeta deposition on basic neurological functions using a longitudinal approach. Animals were phenotyped at different ages corresponding to graded neuropathological stages (from no extracellular Abeta deposition to high amyloid loads). Sensory functions were evaluated by assessing visual and olfactory abilities and did not show any effects of the amyloid precursor protein (APP) transgene. Motor functions were assessed using multiple experimental paradigms. Results showed that motor strength was considerably reduced in APP transgenic mice compared with control animals. No deficit was noted in a motor coordination test although APP transgenic mice displayed decreased locomotion on a stationary beam. Hypolocomotion was also observed in the standard open-field test. Measures of anxiety obtained in the elevated plus-maze show some evidence of hyperanxiety in 15-month-old transgenic mice. Some of the neurological impairments showed by APP mice had an early onset and worsened with progressive aging, in parallel to gradual accumulation of Abeta in brain parenchyma. Relationships between neuropathologically assessed amyloid loads and behavioral deficits were further explored, and it was observed that motor strength deficits were correlated with cortical amyloid burden.

The regular and light-dark Suok tests of anxiety and sensorimotor integration: utility for behavioral characterization in laboratory rodents

Animal behavioral models are crucial for neurobiological research, allowing for the thorough investigation of brain pathogenesis to be performed. In both animals and humans, anxiety has long been linked to vestibular disorders. However, although there are many tests of anxiety and vestibular deficits, there are few protocols that address the interplay between these two domains. The Suok test and its light-dark modification presented here appear to be suitable for testing this pathogenetic link in laboratory rodents. This protocol adds a new dimension to previously used tests by assessing animal anxiety and balancing simultaneously, resulting in efficient, high-throughput screens for testing psychotropic drugs, phenotyping genetically modified animals, and modeling clusters of human disorders related to stress/anxiety and balancing.

Effects of progesterone administration and APPswe+PSEN1Deltae9 mutation for cognitive performance of mid-aged mice

Progesterone (P(4)) and its metabolite, 5alpha-pregnan-3alpha-ol-20-one (3alpha,5alpha-THP) have trophic effects and may improve cognitive function. We investigated the role of progestins in a murine model of Alzheimer's Disease (AD) in which transgenic mice co-overexpress a mutant form of amyloid precursor protein (APPswe) and a deletion in presenilin 1 Delta exon 9 (APPswe+PSEN1Deltae9). We hypothesized that: (1) mice with the APPswe+PSEN1Deltae9 mutation would have performance deficits compared to wildtype mice and (2) long-term administration of P(4) would enhance cognitive performance and increase brain progestin levels over placebo. Mice were ovariectomized at 6 months of age and administered placebo or P(4) via subcutaneously implanted pellets. Mice were tested between 9 and 12 months of age for cognitive performance in the object placement, water maze, object recognition, and T-maze tasks and for motor behavior in an activity monitor and then tissues were collected for steroid measurement. P(4) administration increased progestin levels in cortex, diencephalon, midbrain, and cerebellum of wildtype and mutant mice, but increases in 3alpha,5alpha-THP levels in the hippocampus of APPswe+PSEN1Deltae9 mutant mice were attenuated compared to that observed in wildtype mice. APPswe+PSEN1Deltae9 mice showed poorer performance in hippocampus measures (object placement and water maze tasks). In the object recognition and T-maze task, which are mediated by the cortex and hippocampus, P(4) administration improved performance in both wildtype and APPswe+PSEN1Deltae9 mutant mice compared to placebo administration. Thus, APPswe+PSEN1Delta9 mice have deficits in hippocampal performance and capacity to form 3alpha,5alpha-THP in the hippocampus and both wildtype and APPswe+PSEN1Delta9 mice show beneficial effects of P(4) in cortical function and similar capacity to form 3alpha,5alpha-THP in the cortex.

Impaired spatial learning in the APPSwe�+�PSEN1?E9 bigenic mouse model of Alzheimer?s disease

Mice co-expressing the Swedish amyloid precursor protein mutation (APP(Swe)) and exon 9 deletion (DeltaE9) of the PSEN1 gene begin to develop amyloid plaques at 6-7 months of age. We demonstrate here a spatial learning deficit in 7-month-old APP(Swe) + PSEN1DeltaE9 bigenic mice using an adaptation of the Barnes maze. Mice were first trained on a cued target followed by a hidden-target condition. Although bigenic mice quickly learned the cued-target version of the task, they were significantly impaired when switched to the hidden-target version. In contrast, a separate group of double-transgenic mice trained first on the spatial hidden-target version of the task were unimpaired relative to wild-type controls. We propose that processes such as general rule learning, context learning and exploratory habituation exert a greater influence when the testing environment is novel and overshadow the spatial memory deficit in naive bigenic mice. However, when cued-target training is conducted first, these processes habituate and the spatial learning deficit is unmasked. Seven-month-old APP(Swe) + PSEN1DeltaE9 mice were unimpaired on tests of memory that did not involve learning the rules governing spatial associations.

Diphenyl diselenide changes behavior in female pups

Diphenyl diselenide, (PhSe)(2), is an organoselenium compound that affects a number of neuronal processes. The effect of maternal subcutaneous (s.c.) injection of 25 mg/kg (PhSe)(2) once daily during early postnatal development (from PND 1 to 21) was evaluated in offspring of Wistar rats. The physical and neural reflexes were recorded at pre-weaning period. The behavioral changes in the elevated plus-maze (EPM), open-field and rotarod tasks were performed in 28-day-old pups. Selenium brain status was significantly increased ( approximately 41%) in rat pups. Statistically significant decreases in body weight were observed during lactation period in male and female pups exposed to 25 mg/kg (PhSe)(2). There were no dose-related changes on landmarks indicative of physical and reflexologic parameters of development in rats. (PhSe)(2) induced a disinhibitory effect in EPM behavior according to gender. Specifically, exposure to (PhSe)(2) increased entries and duration in the open arms of the EPM in females but not in males. Locomotor activity and rearing increased by (PhSe)(2) exposure in both male and female offspring in the open field. Both groups were similar in response to motor coordination in the rotarod. We concluded that maternal (PhSe)(2) exposure during lactation increased selenium levels in the pup brain and caused changes on developmental and behavioral parameters of Wistar rat offspring.

Exposure of mothers to diphenyl ditelluride during the suckling period changes behavioral tendencies in their offspring

The long-lasting possible influence of maternal exposure to 0.03 mg/kg of diphenyl ditelluride during the first 14 days of lactational period on later offspring behavior was examined in Wistar rats. Open-field locomotor activity, spontaneous alternation in the T-maze, behavior in the elevated plus-maze, motor coordination in the coat-hanger and rotorod tasks were evaluated in 30 day old pups. There were no significant specific overt signs of maternal intoxication. There were a small (less than 5%) but significant transitory differences in the body weight gain of pups between exposed and control groups, which were apparent from day 30 of suckling. Locomotor activity in the open-field task was similar between telluride and control groups. In the coat-hanger test, the latency before falling for the tellurium group was higher than that of the control group. However, the behavior of both groups was similar in the rotorod test and spontaneous alternation in the T-maze. Tellurium-treated pups presented a higher number of entries and spent more time in the open arms of the elevated plus-maze than control pups. The behavioral alterations observed here after tellurium exposure can be cautiously interpreted as an indication of behavioral disinhibition. In conclusion, this study demonstrated that dam exposure to diphenyl ditelluride can cause subtle behavioral changes in the offspring, which can be related to neurotoxic effects of diphenyl ditelluride.

Exploratory activity and spatial learning in 12-month-old APP695SWE/co+PS1/ΔE9 mice with amyloid plaques

APP(695)SWE/co+PS1/DeltaE9 mice with Abeta plaques in neocortex and hippocampus were evaluated in tests of exploratory activity and spatial learning. On the initial testing day, 12-month-old APP(695)SWE/co+PS1/DeltaE9 mice spent more time than non-transgenic controls in the open arms of the elevated plus-maze. The bigenic group also travelled farther in the central region of the open-field without spending more time there. Only the bigenic group alternated above chance in the T-maze. In the Morris water maze, APP(695)SWE/co+PS1/DeltaE9 mice were impaired during acquisition of the hidden platform sub-task and the probe trial but not in the visible platform test. These results indicate a selective spatial deficit and disinhibitory tendencies in a mouse model with amyloid pathology.