Impaired attention in the 3xTgAD mouse model of Alzheimer's disease: rescue by donepezil (Aricept)

The Effect of Donepezil Hydrochloride in the Twitcher Mouse Model of Krabbe Disease

Krabbe disease (KD) is a rare demyelinating disorder characterized by demyelination caused by mutations in the GALC gene, resulting in toxic accumulation of psychosine. Psychosine has been identified as detrimental to oligodendrocytes, leading to demyelination through diverse hypothesized pathways. Reducing demyelination is essential to maintain neurological function in KD; however, therapeutic interventions are currently limited. Acetylcholinesterase inhibitors (AChEi) are commonly used for symptomatic management of Alzheimer's Disease and are suggested to have potential disease-modifying effects, including regulating myelin state. In particular, donepezil, an AChEi, has demonstrated promising effects in cellular and animal models, including promotion of the expression of myelin-related genes and reduction of glial cell reactivity. This drug also acts as an agonist for sigma-1 receptors (Sig-1R), which are implicated in demyelination diseases. In the context of drug repurposing, here, we demonstrate that administration of donepezil has protective effects in the twitcher mouse model of KD. We provide data showing that donepezil preserves myelin and reduces glial cell reactivity in the brains of twitcher mice. Moreover, donepezil also improves behavioral phenotypes and increases lifespan in twitcher animals. These findings suggest that donepezil, with its dual activity as an AChE inhibitor and Sig-1R agonist, may hold promise as a therapeutic candidate for demyelinating diseases, including KD.

Alzheimer's disease risk gene CD2AP is a dose-sensitive determinant of synaptic structure and plasticity

CD2-Associated protein (CD2AP) is a candidate susceptibility gene for Alzheimer's disease, but its role in the mammalian central nervous system remains largely unknown. We show that CD2AP protein is broadly expressed in the adult mouse brain, including within cortical and hippocampal neurons, where it is detected at pre-synaptic terminals. Deletion of Cd2ap altered dendritic branching and spine density, and impaired ubiquitin-proteasome system activity. Moreover, in mice harboring either one or two copies of a germline Cd2ap null allele, we noted increased paired-pulse facilitation at hippocampal Schaffer-collateral synapses, consistent with a haploinsufficient requirement for pre-synaptic release. Whereas conditional Cd2ap knockout in the brain revealed no gross behavioral deficits in either 3.5- or 12-month-old mice, Cd2ap heterozygous mice demonstrated subtle impairments in discrimination learning using a touchscreen task. Based on unbiased proteomics, partial or complete loss of Cd2ap triggered perturbation of proteins with roles in protein folding, lipid metabolism, proteostasis, and synaptic function. Overall, our results reveal conserved, dose-sensitive requirements for CD2AP in the maintenance of neuronal structure and function, including synaptic homeostasis and plasticity, and inform our understanding of possible cell-type specific mechanisms in Alzheimer's Disease.

Intranasal CEPO-FC prevents attention deficits in streptozotocin-induced rat model of Alzheimer's disease: Focus on synaptic plasticity-related factors

Alzheimer's disease remains an issue of great controversy due to its pathology. It is characterized by cognitive impairments and neuropsychiatric symptoms. The FDA approved medications for this disease, can only mitigate the symptoms. One reason for the lack of effective medications is the inaccessibility of the brain which is encompassed by the blood-brain barrier, making intranasal (IN) route of administration potentially advantageous. Male Wistar rats underwent stereotaxic surgery to induce an Alzheimer's disease model via intracerebroventricular (ICV) streptozotocin injection, and Carbamylated Erythropoietin-Fc (CEPO-FC), a derivative of Erythropoietin without its harmful characteristics, was administered intranasally for ten consecutive days. Cognition performance for memory and attention was assessed using the Novel Object Recognition Test and the Object-Based Attention Test respectively. Depression like behavior was evaluated using the Forced Swim Test. Western blotting was done on the extracted hippocampus to quantify STIM proteins. Calbindin, PSD-95, Neuroplastin, Synaptophysin and GAP-43 genes were assessed by Realtime PCR. Behavioral tests demonstrated that IN CEPO-FC could halt cognition deficits and molecular investigations showed that, STIM proteins were decreased in Alzheimer's model, and increased after IN CEPO-FC treatment. Calbindin and PSD-95 were downregulated in our disease model and upregulated when treated with IN CEPO-FC. While Neuroplastin, and GAP-43 expressions remained unchanged. This study suggests that IN CEPO-FC in low doses could be promising for improving cognition and synaptic plasticity deficits in Alzheimer's disease and since IN route of administration is a convenient way, choosing IN CEPO-FC for clinical trial might worth consideration. See also the graphical abstract(Fig. 1).

Purposive decision-making task in mice using touchscreen operant apparatus

Purposive decision-making, based on sensory input and memory, is a component of executive functioning. Evaluating executive functioning is crucial for understanding neuropsychiatric disorders and brain injuries. However, there's a lack of mouse tests for this purpose. To address this, we developed a novel touchscreen task to assess purposive decision-making in mice. In the present task, the mice had to touch the correct window (left or right), with a visual stimulus as a cue for decision-making. The mice gradually acquired a relationship between the visual stimuli and the action they should take. Each mouse made the correct choice more than 80% of the time based on the visual cue and memory and knowledge of themselves. We could clearly determine when the mice saw the visual cue. The present task offers a valuable tool for investigating the neural mechanisms behind decision-making.

Effect of woohwangchungsimwon and donepezil co-treatment on cognitive function and serum metabolic profiles in a scopolamine-induced model of Alzheimer's disease

ETHNOPHARMACOLOGICAL RELEVANCE

Woohwangchungsimwon (WCW) is a traditional medicine used in East Asian countries to treat central nervous system disorders. Reported pharmacological properties include antioxidant effects, enhanced learning and memory, and protection against ischemic neuronal cell death, supporting its use in treating neurodegenerative diseases like Alzheimer's disease (AD).

AIM OF THE STUDY

The study aims to assess the effects of co-treatment with WCW and donepezil on cognitive functions and serum metabolic profiles in a scopolamine-induced AD model.

MATERIALS AND METHODS

Cell viability and reactive oxygen species (ROS) levels were measured in amyloid β-peptide25-35 (Aβ25-35)-induced SH-SY5Y cells. An AD model was established in ICR mice by intraperitoneal scopolamine administration. Animals underwent the step-through passive avoidance test (PAT) and Morris water maze (MWM) test. Hippocampal tissues were collected to examine specific protein expression. Serum metabolic profiles were analyzed using nuclear magnetic resonance (NMR) spectroscopy.

RESULTS

Co-treatment with WCW and donepezil increased cell viability and reduced ROS production in Aβ25-35-induced SH-SY5Y cells compared to that with donepezil treatment alone. Co-treatment improved cognitive functions and was comparable to donepezil treatment alone in the PAT and MWM tests. Pathways related to tyrosine, phenylalanine, and tryptophan biosynthesis, phenylalanine metabolism, and cysteine and methionine metabolism were altered by co-treatment. Levels of tyrosine and methionine, major serum metabolites in these pathways, were significantly reduced after co-treatment.

CONCLUSIONS

Co-treatment with WCW and donepezil shows promise as a therapeutic strategy for AD and is comparable to donepezil alone in improving cognitive function. Reduced tyrosine and methionine levels after co-treatment may enhance cognitive function by mitigating hypertyrosinemia and hyperhomocysteinemia, known risk factors for AD. The serum metabolic profiles obtained in this study can serve as a foundation for developing other bioactive compounds using a scopolamine-induced mouse model.

Dissection of neuronal circuits underlying sustained attention with the five-choice serial reaction time task

Attention deficits are common in psychiatric and neurological disorders. The transdiagnostic nature of impaired attention suggests a common set of underlying neural circuits. Yet, there are no circuit-based treatments such as non-invasive brain stimulation currently available due to the lack of sufficiently delineated network targets. Therefore, to better treat attentional deficits, a comprehensive functional dissection of neural circuits underlying attention is imperative. This can be achieved by taking advantage of preclinical animal models and well-designed behavioral assays of attention. The resulting findings in turn can be translated to the development of novel interventions with the goal of advancing them to clinical practice. Here we show that the five-choice serial reaction time task has greatly facilitated the study of the neural circuits underlying attention in a well-controlled setting. We first introduce the task and then focus on its application in preclinical studies on sustained attention, especially in the context of state-of-the-art neuronal perturbations.

Longitudinal assessment of cognitive function in the APPswe/PS1dE9 mouse model of Alzheimer's-related beta-amyloidosis

Preclinical models of Alzheimer's disease (AD)-related cognitive decline can be useful for developing therapeutics. The current study longitudinally assessed short-term memory, using a delayed matching-to-position (DMTP) task, and attention, using a 3-choice serial reaction time (3CSRT) task, from approximately 18 weeks of age through death or 72 weeks of age in APPswe/PS1dE9 mice, a widely used mouse model of AD-related amyloidosis. Both transgenic (Tg) and non-Tg mice exhibited improvements in DMTP accuracy over time. Breaks in testing reduced DMTP accuracy but accuracy values quickly recovered in both Tg and non-Tg mice. Both Tg and non-Tg mice exhibited high accuracy in the 3CSRT task with breaks in testing briefly reducing accuracy values equivalently in the 2 genotypes. The current results raise the possibility that deficits in Tg APPswe/PS1dE9 mice involve impairments in learning rather than declines in established performances. A better understanding of the factors that determine whether deficits develop will be useful for designing evaluations of potential pharmacotherapeutics and may reveal interventions for clinical application.

A PAM of the α1A-Adrenergic receptor rescues biomarker, long-term potentiation, and cognitive deficits in Alzheimer's disease mouse models without effects on blood pressure

α1-Adrenergic Receptors (ARs) regulate the sympathetic nervous system by the binding of norepinephrine (NE) and epinephrine (Epi) through different subtypes (α1A, α1B, α1D). α1A-AR activation is hypothesized to be memory forming and cognitive enhancing but drug development has been stagnant due to unwanted side effects on blood pressure. We recently reported the pharmacological characterization of the first positive allosteric modulator (PAM) for the α1A-AR with predictive pro-cognitive and memory properties. In this report, we now demonstrate the in vivo characteristics of Compound 3 (Cmpd-3) in two genetically-different Alzheimer's Disease (AD) mouse models. Drug metabolism and pharmacokinetic studies indicate sufficient brain penetrance and rapid uptake into the brain with low to moderate clearance, and a favorable inhibition profile against the major cytochrome p450 enzymes. Oral administration of Cmpd-3 (3-9 mg/kg QD) can fully rescue long-term potentiation defects and AD biomarker profile (amyloid β-40, 42) within 3 months of dosing to levels that were non-significant from WT controls and which outperformed donepezil (1 mg/kg QD). There were also significant effects on paired pulse facilitation and cognitive behavior. Long-term and high-dose in vivo studies with Cmpd-3 revealed no effects on blood pressure. Our results suggest that Cmpd-3 can maintain lasting therapeutic levels and efficacy with disease modifying effects with a once per day dosing regimen in AD mouse models with no observed side effects.

Muscarinic acetylcholine receptor-dependent and NMDA receptor-dependent LTP and LTD share the common AMPAR trafficking pathway

The forebrain cholinergic system promotes higher brain function in part by signaling through the M₁ muscarinic acetylcholine receptor (mAChR). Long-term potentiation (LTP) and long-term depression (LTD) of excitatory synaptic transmission in the hippocampus are also induced by mAChR. An AMPA receptor (AMPAR) trafficking model for hippocampal neurons has been proposed to simulate N-methyl-D-aspartate receptor (NMDAR)-dependent synaptic plasticity in the early phase. In this study, we demonstrated the validity of the hypothesis that the mAChR-dependent LTP/LTD shares a common AMPAR trafficking pathway associated with NMDAR-dependent LTP/LTD. However, unlike NMDAR, Ca²⁺ influx into the spine cytosol occurs owing to the Ca²⁺ stored inside the ER and is induced via the activation of inositol 1,4,5-trisphosphate (IP3) receptors during M1 mAChR activation. Moreover, the AMPAR trafficking model implies that alterations in LTP and LTD observed in Alzheimer's disease could be attributed to age-dependent reductions in AMPAR expression levels.

Dose-Dependent Dissociation of Pro-cognitive Effects of Donepezil on Attention and Cognitive Flexibility in Rhesus Monkeys

Background

Donepezil exerts pro-cognitive effects by nonselectively enhancing acetylcholine (ACh) across multiple brain systems. Two brain systems that mediate pro-cognitive effects of attentional control and cognitive flexibility are the prefrontal cortex and the anterior striatum, which have different pharmacokinetic sensitivities to ACh modulation. We speculated that these area-specific ACh profiles lead to distinct optimal dose ranges for donepezil to enhance the cognitive domains of attention and flexible learning.

Methods

To test for dose-specific effects of donepezil on different cognitive domains, we devised a multitask paradigm for nonhuman primates that assessed attention and cognitive flexibility. The nonhuman primates received either vehicle or variable doses of donepezil before task performance. We measured intracerebral donepezil and its strength in preventing the breakdown of ACh within the prefrontal cortex and anterior striatum using solid phase microextraction neurochemistry.

Results

The highest administered donepezil dose improved attention and made the subjects more robust against distractor interference, but it did not improve flexible learning. In contrast, only a lower dose range of donepezil improved flexible learning and reduced perseveration, but without distractor-dependent attentional improvement. Neurochemical measurements confirmed a dose-dependent increase of extracellular donepezil and decreases in choline within the prefrontal cortex and the striatum.

Conclusions

The donepezil dose for maximally improving attention differed from the dose range that enhanced cognitive flexibility despite the availability of the drug in two major brain systems supporting these functions. These results suggest that in our cohort of adult monkeys, donepezil traded improvements in attention for improvements in cognitive flexibility at a given dose range.

Neuroprotective effects of donepezil against Aβ25-35-induced neurotoxicity

Purpose

The purpose of this study was to investigate the neuroprotective effect of donepezil against β-amyloid_25-35 (Aβ_25-35)-induced neurotoxicity and the possible mechanism.

Methods

PC12 cells were conventionally cultured. Serial concentrations of Aβ_25-35 and donepezil (0, 0.5, 1, 5, 10, 20 and 50 μmol/L) were added to the PC12 cells, and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) staining was performed to detect the effects of these treatments on PC 12 viability. The PC 12 cells were pretreated with 1, 5, 10, 20 or 50 μmol/L donepezil two hours before 20 μmol/L Aβ_25-35 was added to pretreatment groups A, B, C, D and E. Normal control group I and the 20 μmol/L Aβ_25-35-treated group were selected. An MTT assay was used to detect PC12 cell viability, and the level of lactate dehydrogenase (LDH) was determined. PC12 cells were pretreated with 10 μmol/L GF109203X (a protein kinase C [PKC] antagonist) 30 min before 10 μmol/L donepezil was added to pretreatment group F, and normal control group II, the 10 μmol/L GF109203X-treated group and the 10 μmol/L donepezil-treated group were chosen. The expression of phosphorylation-PKC (P-PKC) and its major substrate phosphorylated myristoylated alanine-rich protein C kinase substrate (P-MARCKS) was measured by Western blotting. The effects of donepezil on the subcellular distribution of the PKCα and PKCε isoforms were detected by immunofluorescence staining.

Results

Treatment with Aβ_25-35 (5, 10, 20 or 50 μmol/L) for 24 h significantly (P < 0.05) decreased PC 12 cell viability in a dose-dependent manner. Compared with the PC12 cells in the control group, those in the 20 μmol/L Aβ_25-35-treated group exhibited lower viability but higher LDH release. Compared with the 20 μmol/L Aβ_25–35-treated group, pretreatment groups B, C, D and E exhibited significantly (P < 0.05) increased cell viability but significantly (P < 0.05) decreased LDH release. Western blotting demonstrated that compared with control, 10 μmol/L donepezil promoted PKC and MARCKS phosphorylation and that the expression of P-PKC and P-MARCKS in pretreatment group F was significantly (P < 0.05) lower than that in the donepezil-treated group. Immunofluorescence staining revealed that the PKCα and PKCε isoforms were located mainly in the cytoplasm of PC12 control cells, whereas donepezil increased the expression of the PKCα and PKCε isoforms in the membrane fraction. The Western blot results showed that donepezil altered the subcellular distribution of the PKCα and PKCε isoforms by decreasing their expression in the cytosolic fraction but increasing their expression in the membrane fraction.

Conclusion

Donepezil can antagonize Aβ_25–350-induced neurotoxicity in PC 12 cells, and PKC activation may account for the neuroprotective effect of donepezil.

Cognitive deficits and altered cholinergic innervation in young adult male mice carrying a Parkinson's disease Lrrk2G2019S knockin mutation

Impaired executive function is a common and debilitating non-motor symptom of idiopathic and hereditary Parkinson's disease (PD), but there is little understanding of the underlying pathophysiological mechanisms and circuits. The G2019S mutation in the kinase domain of leucine-rich repeat kinase 2 (LRRK2) greatly increases risk for late-onset PD, and non-manifesting LRRK2^G2019S carriers can also exhibit early and significant cognitive impairment. Here, we subjected young adult male mice carrying a Lrrk2^G2019S knockin mutation to touchscreen-based operant tasks that measure attention, goal-directed learning and cognitive flexibility, all of which rely on frontal-striatal connectivity and are strongly modulated by cholinergic innervation. In a visuospatial attention task, mutant mice exhibited significantly more omissions and longer response latencies than controls that could not be attributed to deficits in motivation, visual sensory perception per se or locomotion, thereby suggesting impairments in divided attention and/or action-selection as well as generally slower information processing speed. Pretreating mice with the acetylcholinesterase inhibitor donepezil normalized both higher omission rates and longer response latencies in the mutants, but did not affect any performance metric in controls. Strikingly, cholinergic fiber density in cortical areas PL/IL and DMS (dorsomedial striatum) was significantly sparser in mutants than in controls, while further behavioral interrogation of the mutants revealed significant impairments in action-outcome associations but preserved cognitive flexibility. These data suggest that the Lrrk2^G2019S mutation negatively impacts cholinergic innervation anatomically and functionally by young adulthood, impairing corticostriatal network function in ways that may contribute to early PD-associated executive function deficits.

Translational relevance of forward genetic screens in animal models for the study of psychiatric disease

Psychiatric disorders represent a significant burden in our societies. Despite the convincing evidence pointing at gene and gene-environment interaction contributions, the role of genetics in the etiology of psychiatric disease is still poorly understood. Forward genetic screens in animal models have helped elucidate causal links. Here we discuss the application of mutagenesis-based forward genetic approaches in common animal model species: two invertebrates, nematodes (Caenorhabditis elegans) and fruit flies (Drosophila sp.); and two vertebrates, zebrafish (Danio rerio) and mice (Mus musculus), in relation to psychiatric disease. We also discuss the use of large scale genomic studies in human populations. Despite the advances using data from human populations, animal models coupled with next-generation sequencing strategies are still needed. Although with its own limitations, zebrafish possess characteristics that make them especially well-suited to forward genetic studies exploring the etiology of psychiatric disorders.

Acetylcholine deficiency disrupts extratelencephalic projection neurons in the prefrontal cortex in a mouse model of Alzheimer's disease

Short-term memory deficits have been associated with prefrontal cortex (PFC) dysfunction in Alzheimer’s disease (AD) and AD mouse models. Extratelencephalic projection (ET) neurons in the PFC play a key role in short-term working memory, but the mechanism between ET neuronal dysfunction in the PFC and short-term memory impairment in AD is not well understood. Here, using fiber photometry and optogenetics, we found reduced neural activity in the ET neurons in the medial prefrontal cortex (mPFC) of the 5×FAD mouse model led to object recognition memory (ORM) deficits. Activation of ET neurons in the mPFC of 5×FAD mice rescued ORM impairment, and inhibition of ET neurons in the mPFC of wild type mice impaired ORM expression. ET neurons in the mPFC that project to supramammillary nucleus were necessary for ORM expression. Viral tracing and in vivo recording revealed that mPFC ET neurons received fewer cholinergic inputs from the basal forebrain in 5×FAD mice. Furthermore, activation of cholinergic fibers in the mPFC rescued ORM deficits in 5×FAD mice, while acetylcholine deficiency reduced the response of ET neurons in the mPFC to familiar objects. Taken together, our results revealed a neural mechanism behind ORM impairment in 5×FAD mice.

Short-term memory deficits are associated with prefrontal cortex dysfunction in Alzheimer’s disease. Here, the authors assessed extratelencephalic projection (ET) neurons and found reduced ET neural activity in the medial prefrontal cortex (mPFC) and showed ET neurons received fewer cholinergic inputs from the basal forebrain in 5×FAD mice which led to object recognition memory deficits.

Preclinical Evaluation of Attention and Impulsivity Relevant to Determining ADHD Mechanisms and Treatments

People with Attention-Deficit Hyperactivity Disorder (ADHD) exhibit inattention, hyperactivity, and/or impulsivity. Symptoms of ADHD emerge in childhood and can continue throughout adulthood. Clinical assessments to diagnose ADHD can include administration of continuous performance tests (CPTs). CPTs provide an objective measure of inattention, requiring individuals to respond to targets (attention), and inhibit response to non-targets (impulsivity). When investigating the mechanisms of, and novel treatments for, ADHD it is important to measure such behavioral domains (attention and impulsivity). Some well-established preclinical tasks purport to assess attention in rodents but, unlike CPTs, do not require non-target inhibition, limiting their ADHD-relevance.Recently developed tasks recreate CPTs for rodents. The 5-Choice CPT (5C-CPT) contains non-target stimuli, enabling use of signal detection theory to evaluate performance, consistent with CPTs. The 5C-CPT has been adapted for use in humans, enabling direct cross-species comparisons of performance. A newer task, the rodent CPT (rCPT), is a touchscreen-based analog of CPTs, utilizing symbols instead of a simple stimulus array. Currently, the rCPT may be more akin to a go/no-go task, equally presenting targets/non-targets, although numerous variants exist - a strength. The 5C-CPT and rCPT emulate human CPTs and provide the most up-to-date information on ADHD-relevant studies for understanding attention/impulsivity.

Stress-inducible phosphoprotein 1 (HOP/STI1/STIP1) regulates the accumulation and toxicity of α-synuclein in vivo

The predominantly pre-synaptic intrinsically disordered protein α-synuclein is prone to misfolding and aggregation in synucleinopathies, such as Parkinson's disease (PD) and Dementia with Lewy bodies (DLB). Molecular chaperones play important roles in protein misfolding diseases and members of the chaperone machinery are often deposited in Lewy bodies. Here, we show that the Hsp90 co-chaperone STI1 co-immunoprecipitated α-synuclein, and co-deposited with Hsp90 and Hsp70 in insoluble protein fractions in two mouse models of α-synuclein misfolding. STI1 and Hsp90 also co-localized extensively with filamentous S129 phosphorylated α-synuclein in ubiquitin-positive inclusions. In PD human brains, STI1 transcripts were increased, and in neurologically healthy brains, STI1 and α-synuclein transcripts correlated. Nuclear Magnetic Resonance (NMR) analyses revealed direct interaction of α-synuclein with STI1 and indicated that the STI1 TPR2A, but not TPR1 or TPR2B domains, interacted with the C-terminal domain of α-synuclein. In vitro, the STI1 TPR2A domain facilitated S129 phosphorylation by Polo-like kinase 3. Moreover, mice over-expressing STI1 and Hsp90ß presented elevated α-synuclein S129 phosphorylation accompanied by inclusions when injected with α-synuclein pre-formed fibrils. In contrast, reduced STI1 function decreased protein inclusion formation, S129 α-synuclein phosphorylation, while mitigating motor and cognitive deficits as well as mesoscopic brain atrophy in α-synuclein-over-expressing mice. Our findings reveal a vicious cycle in which STI1 facilitates the generation and accumulation of toxic α-synuclein conformers, while α-synuclein-induced proteostatic stress increased insoluble STI1 and Hsp90.

Age-related impairments on the touchscreen paired associates learning (PAL) task in male rats

Discovery research in rodent models of cognitive aging is instrumental for identifying mechanisms of behavioral decline in old age that can be therapeutically targeted. Clinically relevant behavioral paradigms, however, have not been widely employed in aged rats. The current study aimed to bridge this translational gap by testing cognition in a cross-species touchscreen-based platform known as paired-associates learning (PAL) and then utilizing a trial-by-trial behavioral analysis approach. This study found age-related deficits in PAL task acquisition in male rats. Furthermore, trial-by-trial analyses and testing rats on a novel interference version of PAL suggested that age-related impairments were not due to differences in vulnerability to an irrelevant distractor, motivation, or to forgetting. Rather, impairment appeared to arise from vulnerability to accumulating, proactive interference, with aged animals performing worse than younger rats in later trial blocks within a single testing session. The detailed behavioral analysis employed in this study provides new insights into the etiology of age-associated cognitive deficits.

A Preclinical Model of Computerized Cognitive Training: Touchscreen Cognitive Testing Enhances Cognition and Hippocampal Cellular Plasticity in Wildtype and Alzheimer's Disease Mice

With the growing popularity of touchscreen cognitive testing in rodents, it is imperative to understand the fundamental effects exposure to this paradigm can have on the animals involved. In this study, we set out to assess hippocampal-dependant learning in the APP/PS1 mouse model of Alzheimer’s disease (AD) on two highly translatable touchscreen tasks – the Paired Associate Learning (PAL) task and the Trial Unique Non-Matching to Location (TUNL) task. Both of these tests are based on human tasks from the Cambridge Neuropsychological Test Automated Battery (CANTAB) and are sensitive to deficits in both mild cognitive impairment (MCI) and AD. Mice were assessed for deficits in PAL at 9–12 months of age, then on TUNL at 8–11 and 13–16 months. No cognitive deficits were evident in APP/PS1 mice at any age, contrary to previous reports using maze-based learning and memory tasks. We hypothesized that daily and long-term touchscreen training may have inadvertently acted as a cognitive enhancer. When touchscreen-tested mice were assessed on the Morris water maze, they showed improved task acquisition compared to naïve APP/PS1 mice and wild-type (WT) littermate controls. In addition, we show that touchscreen-trained WT and APP/PS1 mice show increased cell proliferation and immature neuron numbers in the dentate gyrus compared to behaviorally naïve WT and APP/PS1 mice. This result indicates that the touchscreen testing paradigm could improve cognitive performance, and/or mask an impairment, in experimental mouse models. This touchscreen-induced cognitive enhancement may involve increased neurogenesis, and possibly other forms of cellular plasticity. This is the first study to show increased numbers of proliferating cells and immature neurons in the hippocampus following touchscreen testing, and that touchscreen training can improve cognitive performance in maze-based spatial navigation tasks. This potential for touchscreen testing to induce cognitive enhancement, or other phenotypic shifts, in preclinical models should be considered in study design. Furthermore, touchscreen-mediated cognitive enhancement could have therapeutic implications for cognitive disorders.

IntelliCage Automated Behavioral Phenotyping Reveals Behavior Deficits in the 3xTg-AD Mouse Model of Alzheimer's Disease Associated With Brain Weight

Transgenic rodent models of Alzheimer’s disease (AD) were designed to study mechanisms of pathogenesis and connect these mechanisms with cognitive decline. Measurements of cognition in rodents can be confounded, however, by human handling and interaction; the IntelliCage was created to circumvent these issues while measuring various facets of cognition in a social environment with water consumption as the primary motivator for task completion. Here, for the first time, we examined the behavioral performance of 3xTg-AD mice in the IntelliCage. Seven- to 9-month-old female 3xTg-AD and non-transgenic (NonTg) mice were tested for 29 days in the IntelliCage to measure prefrontal cortical and hippocampal function. We found that a higher percentage of NonTg mice (86.96%) were able to successfully complete the training (adaptation) phases compared to their 3xTg-AD (57.14%) counterparts. Furthermore, the 3xTg-AD mice showed impairments in attention and working memory. Interestingly, we found that differences in body and brain weight between NonTg and 3xTg-AD mice were associated with whether mice were able to complete the IntelliCage tasks. 3xTg-AD mice that completed IntelliCage tasks had lower cortical insoluble amyloid-β₄₀ fractions than their 3xTg-AD counterparts who failed to complete the tasks. Collectively, these results demonstrate deficits in cognition in the 3xTg-AD mouse and inform scientists of important factors to consider when testing this transgenic model in the IntelliCage.

Sex-Dependent Signatures, Time Frames and Longitudinal Fine-Tuning of the Marble Burying Test in Normal and AD-Pathological Aging Mice

The marble burying (MB) test, a classical test based on the natural tendency of rodents to dig in diverse substrates and to bury small objects, is sensitive to some intrinsic and extrinsic factors. Here, under emerging neuroethological quantitative and qualitative analysis, the MB performance of 12-month-old male and female 3xTg-AD mice for Alzheimer’s disease and age-matched counterparts of gold-standard C57BL6 strain with normal aging unveiled sex-dependent signatures. In addition, three temporal analyses, through the (1) time course of the performance, and (2) a repeated test schedule, identified the optimal time frames and schedules to detect sex- and genotype-dependent differences. Besides, a (3) longitudinal design from 12 to 16 months of age monitored the changes in the performance with aging, worsening in AD-mice, and modulation through the repeated test. In summary, the present results allow us to conclude that (1) the marble burying test is responsive to genotype, sex, aging, and its interactions; (2) the male sex was more sensitive to showing the AD-phenotype; (3) longitudinal assessment shows a reduction in females with AD pathology; (4) burying remains stable in repeated testing; (5) the time-course of marbles burying is useful; and (6) burying behavior most likely represents perseverative and/or stereotyped-like behavior rather than anxiety-like behavior in 3xTg-AD mice.

Using touchscreen-delivered cognitive assessments to address the principles of the 3Rs in behavioral sciences

Despite considerable advances in both in silico and in vitro approaches, in vivo studies that involve animal model systems remain necessary in many research disciplines. Neuroscience is one such area, with studies often requiring access to a complete nervous system capable of dynamically selecting between and then executing a full range of cognitive and behavioral outputs in response to a given stimulus or other manipulation. The involvement of animals in research studies is an issue of active public debate and concern and is therefore carefully regulated. Such regulations are based on the principles of the 3Rs of Replacement, Reduction and Refinement. In the sub-specialty of behavioral neuroscience, Full/Absolute Replacement remains a major challenge, as the complete ex vivo recapitulation of a system as complex and dynamic as the nervous system has yet to be achieved. However, a number of very positive developments have occurred in this area with respect to Relative Replacement and to both Refinement and Reduction. In this review, we discuss the Refinement- and Reduction-related benefits yielded by the introduction of touchscreen-based behavioral assessment apparatus. We also discuss how data generated by a specific panel of behavioral tasks developed for this platform might substantially enhance monitoring of laboratory animal welfare and provide robust, quantitative comparisons of husbandry techniques to define and ensure maintenance of best practice.

Intermittent Hypoxia Training Prevents Deficient Learning-Memory Behavior in Mice Modeling Alzheimer's Disease: A Pilot Study

In mouse models of Alzheimer's disease (AD), normobaric intermittent hypoxia training (IHT) can preserve neurobehavioral function when applied before deficits develop, but IHT's effectiveness after onset of amyloid-β (Aβ) accumulation is unclear. This study tested the hypothesis that IHT improves learning-memory behavior, diminishes Aβ accumulation in cerebral cortex and hippocampus, and enhances cerebrocortical contents of the neuroprotective trophic factors erythropoietin and brain-derived neurotrophic factor (BDNF) in mice manifesting AD traits. Twelve-month-old female 3xTg-AD mice were assigned to untreated 3xTg-AD (n = 6), AD+IHT (n = 6), and AD+sham-IHT (n = 6) groups; 8 untreated wild-type (WT) mice also were studied. AD+IHT mice alternately breathed 10% O2 for 6 min and room air for 4 min, 10 cycles/day for 21 days; AD+sham-IHT mice breathed room air. Spatial learning-memory was assessed by Morris water maze. Cerebrocortical and hippocampal Aβ40 and Aβ42 contents were determined by ELISA, and cerebrocortical erythropoietin and BDNF were analyzed by immunoblotting and ELISA. The significance of time (12 vs. 12 months + 21 days) and treatment (IHT vs. sham-IHT) was evaluated by two-factor ANOVA. The change in swimming distance to find the water maze platform after 21 d IHT (-1.6 ± 1.8 m) differed from that after sham-IHT (+5.8 ± 2.6 m). Cerebrocortical and hippocampal Aβ42 contents were greater in 3xTg-AD than WT mice, but neither time nor treatment significantly affected Aβ40 or Aβ42 contents in the 3xTg-AD mice. Cerebrocortical erythropoietin and BDNF contents increased appreciably after IHT as compared to untreated 3xTg-AD and AD+sham-IHT mice. In conclusion, moderate, normobaric IHT prevented spatial learning-memory decline and restored cerebrocortical erythropoietin and BDNF contents despite ongoing Aβ accumulation in 3xTg-AD mice.

Apamin Improves Prefrontal Nicotinic Impairment in Mouse Model of Alzheimer's Disease

Disruption of attention is an early and disabling symptom of Alzheimer's disease (AD). The underlying cellular mechanisms are poorly understood and treatment options for patients are limited. These early attention deficits are evident in the TgCRND8 mouse, a well-established murine model of AD that recapitulates several features of the disease. Here, we report severe impairment of the nicotinic receptor-mediated excitation of prefrontal attentional circuitry in TgCRND8 mice relative to wild-type littermate controls. We demonstrate that this impairment can be remedied by apamin, a bee venom neurotoxin peptide that acts as a selective antagonist to the SK family of calcium-sensitive potassium channels. We probe this seeming upregulation of calcium-sensitive inhibition and find that the attenuated nicotinic firing rates in TgCRND8 attention circuits are mediated neither by greater cellular calcium signals nor by elevated SK channel expression. Instead, we find that TgCRND8 mice show enhanced functional coupling of nicotinic calcium signals to inhibition. This SK-mediated inhibition exerts a powerful negative feedback on nicotinic excitation, dampening attention-relevant signaling in the TgCRND8 brain. These mechanistic findings identify a new cellular target involved in the modulation of attention and a novel therapeutic target for early attention deficits in AD.

Chemogenetic suppression of anterior cingulate cortical neurons projecting to the visual cortex disrupts attentional behavior in mice

AIM

Attention is a goal-directed cognitive process that facilitates the detection of task-relevant sensory stimuli from dynamic environments. Anterior cingulate cortical area (ACA) is known to play a key role in attentional behavior, but the specific circuits mediating attention remain largely unknown. As ACA modulates sensory processing in the visual cortex (VIS), we aim to test a hypothesis that frontal top-down neurons projecting from ACA to VIS (ACA_VIS ) contributes to visual attention behavior through chemogenetic approach.

METHODS

Adult, male mice were trained to perform the 5-choice serial reaction time task (5CSRTT) using a touchscreen system. An intersectional viral approach was used to selectively express inhibitory designer receptors exclusively activated by designer drugs (iDREADD) or a static fluorophore (mCherry) in ACA_VIS neurons. Mice received counterbalanced injections (i.p.) of the iDREADD ligand (clozapine-N-oxide; CNO) or vehicle (saline) prior to 5CSRTT testing. Finally, mice underwent progressive ratio testing and open field testing following CNO or saline administration.

RESULTS

Chemogenetic suppression of ACA_VIS neuron activity decreased correct task performance during the 5CSRTT mainly driven by an increase in omission and a trending decrease in accuracy with no change in behavioral outcomes associated with motivation, impulsivity, or compulsivity. Breakpoint during the progressive ratio task and distance moved in the open field test were unaffected by ACA_VIS neuron suppression. CNO administration itself had no effect on task performance in mCherry-expressing mice.

CONCLUSION

These results identify long-range frontal-sensory ACA_VIS projection neurons as a key enactor of top-down attentional behavior and may serve as a beneficial therapeutic target.

Alzheimer's Disease Animal Models: Elucidation of Biomarkers and Therapeutic Approaches for Cognitive Impairment

Alzheimer's disease (AD) is an age-related and progressive neurodegenerative disorder. It is widely accepted that AD is mainly caused by the accumulation of extracellular amyloid β (Aβ) and intracellular neurofibrillary tau tangles. Aβ begins to accumulate years before the onset of cognitive impairment, suggesting that the benefit of currently available interventions would be greater if they were initiated in the early phases of AD. To understand the mechanisms of AD pathogenesis, various transgenic mouse models with an accelerated accumulation of Aβ and tau tangles have been developed. However, none of these models exhibit all pathologies present in human AD. To overcome these undesirable phenotypes, APP knock-in mice, which were presented with touchscreen-based tasks, were developed to better evaluate the efficacy of candidate therapeutics in mouse models of early-stage AD. This review assesses several AD mouse models from the aspect of biomarkers and cognitive impairment and discusses their potential as tools to provide novel AD therapeutic approaches.

Longitudinal Assessment of Working Memory Performance in the APPswe/PSEN1dE9 Mouse Model of Alzheimer's Disease Using an Automated Figure-8-Maze

Alzheimer's disease (AD) is a progressive neurodegenerative disorder, with a long preclinical and prodromal phase. To enable the study of disease mechanisms, AD has been modeled in many transgenic animal lines and cognitive functioning has been tested using several widely used behavioral tasks. These tasks, however, are not always suited for repeated longitudinal testing and are often associated with acute stress such as animal transfer, handling, novelty, or stress related to the task itself. This makes it challenging to relate cognitive dysfunction in animal models to cognitive decline observed in AD patients. Here, we designed an automated figure-8-maze (F8M) to test mice in a delayed alternation task (DAT) in a longitudinal manner. Mice were rewarded when they entered alternate sides of the maze on subsequent trials. Automation as well as connection of the F8M set-up with a home cage reduces experimenter interference and minimizes acute stress, thus making it suitable for longitudinal testing and facilitating clinical translation. In the present study, we monitored cognitive functioning of 2-month-old APPswe/PSEN1dE9 (APP/PS1) mice over a period of 4 months. The percentage of correct responses in the DAT did not differ between wild-type and transgenic mice from 2 to 6 months of age. However, 6-month-old mice displayed an increase in the number of consecutive incorrect responses. These results demonstrate the feasibility of longitudinal testing using an automated F8M and suggest that APP/PS1 mice are not impaired at delayed spatial alternation until 6 months of age under the current experimental conditions.

Touchscreen cognitive testing: Cross-species translation and co-clinical trials in neurodegenerative and neuropsychiatric disease

Translating results from pre-clinical animal studies to successful human clinical trials in neurodegenerative and neuropsychiatric disease presents a significant challenge. While this issue is clearly multifaceted, the lack of reproducibility and poor translational validity of many paradigms used to assess cognition in animal models are central contributors to this challenge. Computer-automated cognitive test batteries have the potential to substantially improve translation between pre-clinical studies and clinical trials by increasing both reproducibility and translational validity. Given the structured nature of data output, computer-automated tests also lend themselves to increased data sharing and other open science good practices. Over the past two decades, computer automated, touchscreen-based cognitive testing methods have been developed for non-human primate and rodent models. These automated methods lend themselves to increased standardization, hence reproducibility, and have become increasingly important for the elucidation of the neurobiological basis of cognition in animal models. More recently, there have been increased efforts to use these methods to enhance translational validity by developing task batteries that are nearly identical across different species via forward (i.e., translating animal tasks to humans) and reverse (i.e., translating human tasks to animals) translation. An additional benefit of the touchscreen approach is that a cross-species cognitive test battery makes it possible to implement co-clinical trials-an approach developed initially in cancer research-for novel treatments for neurodegenerative disorders. Co-clinical trials bring together pre-clinical and early clinical studies, which facilitates testing of novel treatments in mouse models with underlying genetic or other changes, and can help to stratify patients on the basis of genetic, molecular, or cognitive criteria. This approach can help to determine which patients should be enrolled in specific clinical trials and can facilitate repositioning and/or repurposing of previously approved drugs. This has the potential to mitigate the resources required to study treatment responses in large numbers of human patients.

Repetitive mild traumatic brain injury in mice triggers a slowly developing cascade of long-term and persistent behavioral deficits and pathological changes

We have previously reported long-term changes in the brains of non-concussed varsity rugby players using magnetic resonance spectroscopy (MRS), diffusion tensor imaging (DTI) and functional magnetic imaging (fMRI). Others have reported cognitive deficits in contact sport athletes that have not met the diagnostic criteria for concussion. These results suggest that repetitive mild traumatic brain injuries (rmTBIs) that are not severe enough to meet the diagnostic threshold for concussion, produce long-term consequences. We sought to characterize the neuroimaging, cognitive, pathological and metabolomic changes in a mouse model of rmTBI. Using a closed-skull model of mTBI that when scaled to human leads to rotational and linear accelerations far below what has been reported for sports concussion athletes, we found that 5 daily mTBIs triggered two temporally distinct types of pathological changes. First, during the first days and weeks after injury, the rmTBI produced diffuse axonal injury, a transient inflammatory response and changes in diffusion tensor imaging (DTI) that resolved with time. Second, the rmTBI led to pathological changes that were evident months after the injury including: changes in magnetic resonance spectroscopy (MRS), altered levels of synaptic proteins, behavioural deficits in attention and spatial memory, accumulations of pathologically phosphorylated tau, altered blood metabolomic profiles and white matter ultrastructural abnormalities. These results indicate that exceedingly mild rmTBI, in mice, triggers processes with pathological consequences observable months after the initial injury.

Pharmacological investigations on efficacy of Phlorizin a sodium-glucose co-transporter (SGLT) inhibitor in mouse model of intracerebroventricular streptozotocin induced dementia of AD type

OBJECTIVES

The study has been commenced to discover the potential of Phlorizin (dual SGLT inhibitor) in streptozotocin induced dementia of Alzheimer's disease (AD) type.

MATERIAL AND METHODS

Injection of Streptozotocin (STZ) was given via i.c.v. route (3 mg/kg) to induce dementia of Alzheimer's type. In these animals learning and memory was evaluated using Morris water maze (MWM) test. Glutathione (GSH) and thiobarbituric acid reactive species (TBARS) level was quantified to evaluate the oxidative stress; cholinergic activity of brain was estimated in term of acetylcholinesterase (AChE) activity; and the levels of myeloperoxidase (MPO) were measured as inflammation marker.

RESULTS

The mice model had decreased performance in MWM, representing impairment of cognitive functions. Biochemical evaluation showed rise in TBARS level, MPO and AChE activity, and fall in GSH level. The histopathological study revealed severe infiltration of neutrophils. In the study, Phlorizin/Donepezil (serving as positive control) treatment mitigate streptozotocin induced cognitive decline, histopathological changes and biochemical alterations.

CONCLUSIONS

The results suggest that Phlorizin decreased cognitive function via its anticholinesterase, antioxidative, antiinflammatory effects and probably through SGLT inhibitory action. It can be conferred that SGLTs can be an encouraging target for the treatment of dementia of AD.

Conditioning learning in an attentional task relates to age and ventricular expansion in a nonhuman primate (Microcebus murinus)

The grey mouse lemur (Microcebus murinus) is a promising nonhuman primate model for brain ageing and neurodegenerative diseases. Age-related cognitive decline in this model is well described, however, data on possible relations between attention and age, as they are known from humans, are missing. We tested 10 mouse lemurs in a touchscreen-based version of the 5-choice-serial-reaction-time-task (5CSRTT) on visuo-spatial attention: subjects had to interact with a briefly presented stimulus occurring unpredictably in one out of five locations on the touchscreen. Animals were trained to an 80 % performance at a four seconds stimulus presentation duration (SPD) and subsequently challenged by a SPD of two seconds. Additionally, ventricular expansion was assessed using structural magnetic resonance imaging. Trials to the 80 % criterion at four seconds SPD correlated significantly with age and with ventricular expansion, especially around the occipital lobe. Once criterion performance was reached, two seconds challenge performance was independent of age. In four subjects that were additionally challenged with 1.5, 1.0, 0.8, or 0.6 s SPDs or variable delays preceding stimulus presentation, performance linearly declined with decreasing SPD, i.e. increasing attentional demand. In conclusion, this is the first report of 5CSRTT data in mouse lemurs and demonstrates the general applicability of this task of visuo-spatial attention to this nonhuman primate model. Results further demonstrate age-related deficits in learning during acquisition of the 5CSRTT and suggest that both may be linked through age-related atrophy of occipital structures and a resulting deficit in central visual processes.

New frontiers in translational research: Touchscreens, open science, and the mouse translational research accelerator platform

Many neurodegenerative and neuropsychiatric diseases and other brain disorders are accompanied by impairments in high-level cognitive functions including memory, attention, motivation, and decision-making. Despite several decades of extensive research, neuroscience is little closer to discovering new treatments. Key impediments include the absence of validated and robust cognitive assessment tools for facilitating translation from animal models to humans. In this review, we describe a state-of-the-art platform poised to overcome these impediments and improve the success of translational research, the Mouse Translational Research Accelerator Platform (MouseTRAP), which is centered on the touchscreen cognitive testing system for rodents. It integrates touchscreen-based tests of high-level cognitive assessment with state-of-the art neurotechnology to record and manipulate molecular and circuit level activity in vivo in animal models during human-relevant cognitive performance. The platform also is integrated with two Open Science platforms designed to facilitate knowledge and data-sharing practices within the rodent touchscreen community, touchscreencognition.org and mousebytes.ca. Touchscreencognition.org includes the Wall, showcasing touchscreen news and publications, the Forum, for community discussion, and Training, which includes courses, videos, SOPs, and symposia. To get started, interested researchers simply create user accounts. We describe the origins of the touchscreen testing system, the novel lines of research it has facilitated, and its increasingly widespread use in translational research, which is attributable in part to knowledge-sharing efforts over the past decade. We then identify the unique features of MouseTRAP that stand to potentially revolutionize translational research, and describe new initiatives to partner with similar platforms such as McGill's M3 platform (m3platform.org).

Adolescent frontal top-down neurons receive heightened local drive to establish adult attentional behavior in mice

Frontal top-down cortical neurons projecting to sensory cortical regions are well-positioned to integrate long-range inputs with local circuitry in frontal cortex to implement top-down attentional control of sensory regions. How adolescence contributes to the maturation of top-down neurons and associated local/long-range input balance, and the establishment of attentional control is poorly understood. Here we combine projection-specific electrophysiological and rabies-mediated input mapping in mice to uncover adolescence as a developmental stage when frontal top-down neurons projecting from the anterior cingulate to visual cortex are highly functionally integrated into local excitatory circuitry and have heightened activity compared to adulthood. Chemogenetic suppression of top-down neuron activity selectively during adolescence, but not later periods, produces long-lasting visual attentional behavior deficits, and results in excessive loss of local excitatory inputs in adulthood. Our study reveals an adolescent sensitive period when top-down neurons integrate local circuits with long-range connectivity to produce attentional behavior.

Translational cognitive neuroscience of dementia with touchscreen operant chambers

Translational cognitive neuroscience of dementia involves mainly two areas: the validation of newly developed dementia animal models and the preclinical assessment of novel drug candidates in such model animals. To validate new animal models, a multidomain panel (battery) approach is essential in that dementia is, by definition, not merely a memory disorder but rather a multidomain cognitive/behavior disorder: animal modeling with a certain type of dementia would develop cognitive impairments in multiple (two at minimum) domains in a specific order according to unique spreading patterns of its neuropathology. In new drug development, the availability of highly sensitive tools assessing animal cognition is crucial to the detection of cognitive decline at the earliest stage of the disease, which may be an optimal time point to test a drug candidate. Using interspecies translatable (analogous) cognitive tasks would also be necessary to successfully predict the efficacy of drug candidates in subsequent clinical trials. Currently, this translational prediction is seriously limited given discrepancies in behavioral assessment methods between animals and humans in the preclinical and clinical trials, respectively. Since neurodegenerative diseases are often accompanied by not only cognitive but also affective and movement disorders, simultaneous assessment of task-relevant locomotor behavior and motivation is also important to rule out the effects of potential confounders. The touchscreen operant platform may satisfy these needs by offering several advantages over conventional methodology. In this review, we discuss the touchscreen operant chamber system and highlight some of its qualities as a promising and desirable tool for translational research of dementia.

Therapeutic Effects of Apamin as a Bee Venom Component for Non-Neoplastic Disease

Bee venom is a natural toxin produced by honeybees and plays an important role in defending bee colonies. Bee venom has several kinds of peptides, including melittin, apamin, adolapamine, and mast cell degranulation peptides. Apamin accounts for about 2%-3% dry weight of bee venom and is a peptide neurotoxin that contains 18 amino acid residues that are tightly crosslinked by two disulfide bonds. It is well known for its pharmacological functions, which irreversibly block Ca2+-activated K+ (SK) channels. Apamin regulates gene expression in various signal transduction pathways involved in cell development. The aim of this study was to review the current understanding of apamin in the treatment of apoptosis, fibrosis, and central nervous system diseases, which are the pathological processes of various diseases. Apamin's potential therapeutic and pharmacological applications are also discussed.

Sex differences in the effect of maternal immune activation on cognitive and psychosis-like behaviour in Long Evans rats

Maternal immune activation during pregnancy is associated with increased risk of development of schizophrenia in later life. There are sex differences in schizophrenia, particularly in terms of age of onset, course of illness and severity of symptoms. However, there is limited and inconsistent literature on sex differences in the effects of maternal immune activation on behaviour with relevance to schizophrenia. The aim of this study was therefore to investigate sex differences in the effects of maternal immune activation by treating Long Evans rats with poly(I:C) on gestational day 15. We compared adult male and female offspring on spatial working memory in the touchscreen trial-unique nonmatching-to-location task, pairwise discrimination and reversal learning, as well as on prepulse inhibition and psychotropic drug-induced locomotor hyperactivity. Male, but not female poly(I:C) offspring displayed a deficit in spatial working memory, particularly at the longer delay. Neither pairwise discrimination nor reversal learning showed an effect of poly(I:C), but female controls outperformed male controls in the reversal learning task. Significant reduction of prepulse inhibition and enhancement of acute methamphetamine-induced locomotor hyperactivity was found similarly in male and female poly(I:C) offspring. These results show that maternal immune activation induces a range of behavioural effects in the offspring, with sex specificity in the effects of maternal immune activation on some aspects of cognition, but not psychosis-like behaviour.

β-lactolin, a whey-derived glycine-threonine-tryptophan-tyrosine lactotetrapeptide, improves prefrontal cortex-associated reversal learning in mice

Dementia and cognitive decline have become worldwide public health problems. We have previously reported that a whey-derived glycine-threonine-tryptophan-tyrosine peptide, β-lactolin, improves hippocampus-dependent memory functions in mice. The supplementation with a whey digest rich in β-lactolin improves memory retrieval and executive function in a clinical trial, but the effect of β-lactolin on prefrontal cortex (PFC)-associated cognitive function was unclear. Here we examined the effect of β-lactolin and the whey digest on PFC-associated visual discrimination (VD) and reversal discrimination (RD) learning, using a rodent touch panel-based operant system. β-Lactolin and the whey digest significantly improved the RD learning, and the whey digest enhanced the response latency during the VD task, indicating that β-lactolin and the whey digest improve PFC-associated cognitive functions. Given the translational advantages of the touch panel operant system, consumption of β-lactolin in daily life could be beneficial for improving human PFC-associated cognitive function, helping to prevent dementia.

MouseBytes, an open-access high-throughput pipeline and database for rodent touchscreen-based cognitive assessment

Open Science has changed research by making data accessible and shareable, contributing to replicability to accelerate and disseminate knowledge. However, for rodent cognitive studies the availability of tools to share and disseminate data is scarce. Automated touchscreen-based tests enable systematic cognitive assessment with easily standardised outputs that can facilitate data dissemination. Here we present an integration of touchscreen cognitive testing with an open-access database public repository (mousebytes.ca), as well as a Web platform for knowledge dissemination (https://touchscreencognition.org). We complement these resources with the largest dataset of age-dependent high-level cognitive assessment of mouse models of Alzheimer’s disease, expanding knowledge of affected cognitive domains from male and female mice of three strains. We envision that these new platforms will enhance sharing of protocols, data availability and transparency, allowing meta-analysis and reuse of mouse cognitive data to increase the replicability/reproducibility of datasets.

Beneficial effects of curtailing immune susceptibility in an Alzheimer's disease model

BACKGROUND

Currently, there are no effective therapeutic options for Alzheimer's disease, the most common, multifactorial form of dementia, characterized by anomalous amyloid accumulation in the brain. Growing evidence points to neuroinflammation as a major promoter of AD. We have previously shown that the proinflammatory cytokine TNFSF10 fuels AD neuroinflammation, and that its immunoneutralization results in improved cognition in the 3xTg-AD mouse.

METHODS

Here, we hypothesize that inflammatory hallmarks of AD might parallel with central and peripheral immune response dysfunction. To verify such hypothesis, we used a triple transgenic mouse model of AD. 3xTg-AD mice were treated for 12 months with an anti-TNFSF10 antibody, and thereafter immune/inflammatory markers including COX2, iNOS, IL-1β and TNF-α, CD3, GITR, and FoxP3 (markers of regulatory T cells) were measured in the spleen as well as in the hippocampus.

RESULTS

Spleens displayed accumulation of amyloid-β1-42 (Aβ1-42), as well as high expression of Treg cell markers FoxP3 and GITR, in parallel with the increased levels of inflammatory markers COX2, iNOS, IL-1β and TNF-α, and blunted IL-10 expression. Moreover, CD3 expression was increased in the hippocampus, consistently with FoxP3 and GITR. After chronic treatment of 3xTg-AD mice with an anti-TNFSF10 antibody, splenic FoxP3, GITR, and the above-mentioned inflammatory markers expression was restored to basal levels, while expression of IL-10 was increased. A similar picture was observed in the hippocampus. Such improvement of peripheral and CNS inflammatory/immune response was associated with decreased microglial activity in terms of TNFα production, as well as decreased expression of both amyloid and phosphorylated tau protein in the hippocampus of treated 3xTg-AD mice. Interestingly, we also reported an increased expression of both CD3 and FoxP3, in sections from human AD brain.

CONCLUSIONS

We suggest that neuroinflammation in the brain of 3xTg-AD mice triggered by TNFSF10 might result in a more general overshooting of the immune response. Treatment with an anti-TNFSF10 antibody blunted inflammatory processes both in the spleen and hippocampus. These data confirm the detrimental role of TNFSF10 in neurodegeneration, and corroborate the hypothesis of the anti-TNFSF10 strategy as a potential treatment to improve outcomes in AD.

A Touchscreen Motivation Assessment Evaluated in Huntington's Disease Patients and R6/1 Model Mice

Apathy is pervasive across many neuropsychiatric disorders but is poorly characterized mechanistically, so targeted therapeutic interventions remain elusive. A key impediment has been the lack of validated assessment tools to facilitate translation of promising findings between preclinical disease models and patients. Apathy is a common symptom in Huntington's disease. Due to its established genetic basis and the availability of defined animal models, this disease offers a robust translational framework for linking motivated behavior with underlying neurobiology and an ideal context in which to evaluate a quantitative, translational apathy assessment method. In this study we therefore aimed to demonstrate the validity of using touchscreen-delivered progressive ratio tasks to mirror apathy assessment in Huntington's disease patients and a representative mouse model. To do this we evaluated Huntington's disease patients (n = 23) and age-matched healthy controls (n = 20), and male R6/1 mice (n = 23) and wildtype controls (n = 29) for apathy-like behavior using touchscreen-delivered progressive ratio tasks. The primary outcome measure of the assessment was breakpoint, defined as the highest number of touchscreen responses emitted before task engagement ceased. Patients and R6/1 mice were both found to exhibit significantly reduced breakpoints relative to their respective control groups, consistent with apathy-like behavior. This performance was also not associated with motoric differences in either species. These data demonstrate the utility of touchscreen-delivered progressive ratio tasks in detecting clinically relevant motivational deficits in Huntington's disease. This approach may offer a platform from which clinically relevant mechanistic insights concerning motivation symptoms can be derived and provide an effective route for translation of promising preclinical findings into viable therapeutic interventions.

Donepezil increases resistance to induced seizures in a mouse model of Dravet syndrome

De novo loss-of-function mutations in SCN1A are the main cause of Dravet syndrome, a catastrophic encephalopathy characterized by recurrent early-life febrile seizures, a number of other afebrile seizure types that are often refractory to treatment, and behavioral abnormalities including social deficits, motor dysfunction, and cognitive impairment. We previously demonstrated that the reversible acetylcholinesterase inhibitor, Huperzine A, increases seizure resistance in Scn1a mutants. In the present study, we evaluated the therapeutic potential of donepezil, a reversible acetylcholinesterase inhibitor approved by the Food and Drug Administration, in a mouse model of Dravet syndrome (Scn1a^+/- ). We found that donepezil conferred robust protection against induced seizures in Scn1a^+/- mutants.

The Arctic/Swedish APP mutation alters the impact of chronic stress on cognition in mice

Chronic stress is a major risk factor for developing Alzheimer's disease (AD) and promotes the processing of amyloid precursor protein (APP) to β-amyloid (Aβ). However, the precise relationship of stress and disease-typical cognitive decline is presently not well understood. The aim of this study was to investigate how early life stress may affect cognition in adult mice with and without soluble Aβ pathology typical for the early stages of the disease. We focussed on sustained attention and response control, aspects of cognition mediated by the prefrontal cortex that are consistently impaired both in early AD and after chronic stress exposure. Young wild-type mice as well as transgenic arcAβ mice overexpressing the hAPParc/swe transgene were exposed to a chronic unpredictable stress paradigm (age 3-8 weeks). At 15 weeks, these mice were tested on the 5-choice serial reaction time task, a test of sustained attention and executive control. We found that, expectedly, chronic stress increased impulsive choices and impaired sustained attention in wild-type mice. However, the same treatment reduced impulsivity and did not interfere with sustained attention in arcAβ mice. These findings suggest an unexpected interaction between chronic stress and Aβ whereby Aβ-pathology caused by the hAPParc/swe mutation prevented and/or reversed stress-induced cognitive changes through mechanisms that deserve further investigation. They also indicate that Aβ, in modest amounts, may have a beneficial role for cognitive stability, for example by protecting neural networks from the impact of further physiological or behavioural stress.

Evaluation of attention in APP/PS1 mice shows impulsive and compulsive behaviours

While Alzheimer's disease (AD) is traditionally associated with deficits in episodic memory, early changes in other cognitive domains, such as attention, have been gaining interest. In line with clinical observations, some animal models of AD have been shown to develop attentional deficits, but this is not consistent across all models. The APPswe/PS1ΔE9 (APP/PS1) mouse is one of the most commonly used AD models and attention has not yet been scrutinised in this model. We set out to assess attention using the 5-choice serial reaction time task (5CSRTT) early in the progression of cognitive symptoms in APP/PS1 mice, using clinically translatable touchscreen chambers. APP/PS1 mice showed no attentional changes across 5CSRTT training or any probes from 9 to 11 months of age. Interestingly, APP/PS1 mice showed increased impulsive and compulsive responding when task difficulty was high. This suggests that while the APP/PS1 mouse model may not be a good model of attentional changes in AD, it may be useful to study the early changes in impulsive and compulsive behaviour that have been identified in patient studies. As these changes have not previously been reported without attentional deficits in the clinic, the APP/PS1 mouse model may provide a unique opportunity to study these specific behavioural changes seen in AD, including their mechanistic underpinnings and therapeutic implications.

A longitudinal multimodal in vivo molecular imaging study of the 3xTg-AD mouse model shows progressive early hippocampal and taurine loss

The understanding of the natural history of Alzheimer's disease (AD) and temporal trajectories of in vivo molecular mechanisms requires longitudinal approaches. A behavioral and multimodal imaging study was performed at 4/8/12 and 16 months of age in a triple transgenic mouse model of AD (3xTg-AD). Behavioral assessment included the open field and novel object recognition tests. Molecular characterization evaluated hippocampal levels of amyloid β (Aβ) and hyperphosphorylated tau. Magnetic resonance imaging (MRI) included assessment of hippocampal structural integrity, blood-brain barrier (BBB) permeability and neurospectroscopy to determine levels of the endogenous neuroprotector taurine. Longitudinal brain amyloid accumulation was assessed using 11C Pittsburgh compound B positron emission tomography (PET), and neuroinflammation/microglia activation was investigated using 11C-PK1195. We found altered locomotor activity at months 4/8 and 16 months and recognition memory impairment at all time points. Substantial early reduction of hippocampal volume started at month 4 and progressed over 8/12 and 16 months. Hippocampal taurine levels were significantly decreased in the hippocampus at months 4/8 and 16. No differences were found for amyloid and neuroinflammation with PET, and BBB was disrupted only at month 16. In summary, 3xTg-AD mice showed exploratory and recognition memory impairments, early hippocampal structural loss, increased Aβ and hyperphosphorylated tau and decreased levels of taurine. In sum, the 3xTg-AD animal model mimics pathological and neurobehavioral features of AD, with early-onset recognition memory loss and MRI-documented hippocampal damage. The early-onset profile suggests temporal windows and opportunities for therapeutic intervention, targeting endogenous neuroprotectors such as taurine.

Impaired Reversal Learning in APPPS1-21 Mice in the Touchscreen Visual Discrimination Task

Preclinical-clinical translation of cognitive functions has been difficult in Alzheimer's disease (AD) research but is crucial to the (predictive) validity of AD animal models. Reversal learning, a representation of flexibility and adaptability to a changing environment, might represent such a translatable feature of human cognition. We, therefore, examined visual discrimination (VD) and reversal learning in the APPPS1-21 mouse model of amyloid-based AD pathology. We used touchscreen operant cages in novel and translationally valid, as well as objective testing methodology that minimizes within- or between-trial handling. Mice were trained to associate a visual cue with a food reward (VD learning), and subsequently learned to adjust their response when this rule changed (reversal learning). We assessed performance at two different ages, namely at 6 months of age, considered an early disease stage, and at 9 months, a stage of established pathology. Both at 6 and 9 months, transgenic animals needed more sessions to reach criterion performance, compared to wild-type controls. Overall, transgenic animals do not show a general cognitive, motivational or motor deficit, but experience specific difficulties to adapt to reward contingency changes, already at an early pathology stage.

Age, but not severity of injury, mediates decline in executive function: Validation of the rodent touchscreen paradigm for preclinical models of traumatic brain injury

Increasingly, it is being recognised that traumatic brain injury (TBI) is not just an acute event but instead results in ongoing neuronal injury that may lead to chronic impairments in multiple cognitive domains. Of these, deficits in executive function are one of the more common changes reported following TBI, and are a major predictor of well-being, social function and quality of life in individuals with a history of TBI. In order to fully understand the relationship between TBI and executive dysfunction, including brain mechanisms that may account for this, experimental models are clearly needed. However, to date, there have been a lack of preclinical studies systematically comparing the effect of injury severity on executive function, particularly at long-term timepoints post-injury. Furthermore, many previous studies have not used behavioural measures that are sensitive to the full range of executive function impairments that may manifest after injury, particularly in models of diffuse axonal injury (Lv et al.). The current study aimed to investigate the temporal profile, up to 12 months post-injury, of the evolution of executive dysfunction following different severities of injury in an experimental model of DAI. In order to do so, we utilised a rodent touchscreen paradigm to administer the 5 Choice- Continuous Performance Task (5C-CPT), an extension of the 5-choice serial reaction time task (5CSRT). Interestingly, there were no differences in learning, motivation, attention, response time or impulsivity at 1 month, 6 months or 12 months post-injury in any of the TBI groups compared to sham, regardless of the initial severity of the injury. Instead, most of the effects on executive function seen at the 12 month timepoint appeared to be a result of ageing, not injury. As even the 12-month timepoint represents middle age in the rat, future studies will be needed to further probe these effects, in order to determine whether DAI may influence the presentation of executive dysfunction in older age.

Hippocampal Proteomic Alteration in Triple Transgenic Mouse Model of Alzheimer's Disease and Implication of PINK 1 Regulation in Donepezil Treatment

Donepezil is a clinically approved acetylcholinesterase inhibitor (AChEI) for cognitive improvement in Alzheimer's disease (AD). Donepezil has been used as a first-line agent for the symptomatic treatment of AD, but its ability to modify disease pathology and underlying mechanisms is not clear. We investigated the protective effects and underlying mechanisms of donepezil in AD-related triple transgenic (APP_Swe/PSEN1_M146V/MAPT_P301L) mouse model (3×Tg-AD). Mice (8-month old) were treated with donepezil (1.3 mg/kg) for 4 months and evaluated by behavioral tests for assessment of cognitive functions, and the hippocampal tissues were examined by protein analysis and quantitative proteomics. Behavioral tests showed that donepezil significantly improved the cognitive capabilities of 3×Tg-AD mice. The levels of soluble and insoluble amyloid beta proteins (Aβ_1-40 and Aβ_1-42) and senile plaques were reduced in the hippocampus. Golgi staining of the hippocampus showed that donepezil prevented dendritic spine loss in hippocampal neurons of 3×Tg-AD mice. Proteomic studies of the hippocampal tissues identified 3131 proteins with altered expression related to AD pathology, of which 262 could be significantly reversed with donepezil treatment. Bioinformatics with functional analysis and protein-protein interaction (PPI) network mapping showed that donepezil significantly elevated the protein levels of PINK 1, NFASC, MYLK2, and NRAS in the hippocampus, and modulated the biological pathways of axon guidance, mitophagy, mTOR, and MAPK signaling. The substantial upregulation of PINK 1 with donepezil was further verified by Western blotting. Donepezil exhibited neuroprotective effects via multiple mechanisms. In particular, PINK 1 is related to mitophagy and cellular protection from mitochondrial dysfunction, which might play important roles in AD pathogenesis and represent a potential therapeutic target.

Sex differences in the timing behavior performance of 3xTg-AD and wild-type mice in the peak interval procedure

We investigated interval timing behavior of 10-month-old male and female 3xTg-AD mice compared with their B6129F2/J wild type controls using the peak interval procedure with a 15 s target interval. Multiple parameters reflecting different aspects of timing performance were extracted from steady-state anticipatory nose-poking behavior using two different approaches: single trial analyses and average response curve analyses. These measures can dissociate the differences in performance due to distortions in the interval timing ability or to motivational decline (i.e. apathy); both of which have been reported in Alzheimer patients. We found that the interval timing ability of male and female 3xTg-AD mice did not differ from wild-type controls. However, in measures reflecting motivational state, we found significant sex differences regardless of genotype. Specifically, female mice initiated anticipatory responding later in the trial and had lower response amplitudes than males. Although our findings can also be interpreted in terms of differences in temporal control for response initiation, they more strongly suggest the effect of differential incentive motivation between sexes on timing behavior in these mice.

PDE3 Inhibitors Repurposed as Treatments for Age-Related Cognitive Impairment

As the population of older individuals grows worldwide, researchers have increasingly focused their attention on identifying key molecular targets of age-related cognitive impairments, with the aim of developing possible therapeutic interventions. Two such molecules are the intracellular cyclic nucleotides, cAMP and cGMP. These second messengers mediate fundamental aspects of brain function relevant to memory, learning, and cognitive function. Consequently, phosphodiesterases (PDEs), which hydrolyze cAMP and cGMP, are promising targets for the development of cognition-enhancing drugs. Inhibitors that target PDEs work by elevating intracellular cAMP. In this review, we provide an overview of different PDE inhibitors, and then we focus on pharmacological and physiological effects of PDE3 inhibitors in the CNS and peripheral tissues. Finally, we discuss findings from experimental and preliminary clinical studies and the potential beneficial effects of the PDE3 inhibitor cilostazol on age-related cognitive impairments. In the innovation pipeline of pharmaceutical development, the antiplatelet agent cilostazol has come into the spotlight as a novel treatment for mild cognitive impairment. Overall, the repurposing of cilostazol may represent a potentially promising way to treat mild cognitive impairment, Alzheimer's disease, and vascular dementia. In this review, we present a brief summary of cAMP signaling and different PDE inhibitors, followed by a discussion of the pharmacological and physiological role of PDE3 inhibitors. In this context, we discuss the repurposing of a PDE3 inhibitor, cilostazol, as a potential treatment for age-related cognitive impairment based on recent research.