Animal Models Of Brain Diseases Research Articles

Healthy blood, healthy brain: a window into understanding and treating neurodegenerative diseases.

Our limited understanding of complex neurodegenerative disorders has held us back on the development of efficient therapies. While several approaches are currently being considered, it is still unclear what will be most successful. Among the latest and more novel ideas, the concept of blood or plasma transfusion from young healthy donors to diseased patients is gaining momentum and attracting attention beyond the scientific arena. While young orhealthy blood is enriched with protective and restorative components, blood from older subjects may accumulate neurotoxic agents or be impoverished of beneficial factors. In this commentary, we present an overview of the compelling evidence collected in various animal models of brain diseases (e.g., Alzheimer, Parkinson, Huntington) to the actual clinical trials that have been conducted to test the validity of blood-related treatments in neurodegenerative diseases and argue in favor of such approach.

Behavioral tests for evaluating the characteristics of brain diseases in rodent models: Optimal choices for improved outcomes (Review).

Behavioral assessment is the dominant approach for evaluating whether animal models of brain diseases can successfully mimic the clinical characteristics of diseases. At present, most research regarding brain diseases involves the use of rodent models. While studies have reported numerous methods of behavioral assessments in rodent models of brain diseases, each with different principles, procedures, and assessment criteria, only few reviews have focused on characterizing and differentiating these methods based on applications for which they are most appropriate. Therefore, in the present review, the representative behavioral tests in rodent models of brain diseases were compared and differentiated, aiming to provide convenience for researchers in selecting the optimal methods for their studies.

Designed Peptide Inhibitors of STEP Phosphatase-GluA2 AMPA Receptor Interaction Enhance the Cognitive Performance in Rats.

Cognitive impairment and learning ability of the brain are directly linked to synaptic plasticity as measured in changes of long-term potentiation (LTP) and long-term depression (LTD) in animal models of brain diseases. LTD reflects a sustained reduction of the synaptic AMPA receptor content based on targeted clathrin-mediated endocytosis. AMPA receptor endocytosis is initiated by dephosphorylation of Tyr876 on the C-terminus of the AMPAR subunit GluA2. The brain-specific striatal-enriched protein tyrosine phosphatase (STEP) is responsible for this process. To identify new, highly effective inhibitors of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) internalization, we performed structure-based design of peptides able to inhibit STEP-GluA2-CT complex formation. Two short peptide derivatives were found as efficient in vitro inhibitors. Our in vivo experiments evidenced that both peptides restore the memory deficits and display anxiolytic and antidepressant effects in a scopolamine-treated rat model. The interference peptides identified and characterized here represent promising lead compounds for novel cognitive enhancers and/or behavioral modulators.

Effects of intranasal guanosine administration on brain function in a rat model of ischemic stroke.

Ischemic stroke is a major cause of morbidity and mortality worldwide and only few affected patients are able to receive treatment, especially in developing countries. Detailed pathophysiology of brain ischemia has been extensively studied in order to discover new treatments with a broad therapeutic window and that are accessible to patients worldwide. The nucleoside guanosine (Guo) has been shown to have neuroprotective effects in animal models of brain diseases, including ischemic stroke. In a rat model of focal permanent ischemia, systemic administration of Guo was effective only when administered immediately after stroke induction. In contrast, intranasal administration of Guo (In-Guo) was effective even when the first administration was 3 h after stroke induction. In order to validate the neuroprotective effect in this larger time window and to investigate In-Guo neuroprotection under global brain dysfunction induced by ischemia, we used the model of thermocoagulation of pial vessels in Wistar rats. In our study, we have found that In-Guo administered 3 h after stroke was capable of preventing ischemia-induced dysfunction, such as bilateral suppression and synchronicity of brain oscillations and ipsilateral cell death signaling, and increased permeability of the blood-brain barrier. In addition, In-Guo had a long-lasting effect on preventing ischemia-induced motor impairment. Our data reinforce In-Guo administration as a potential new treatment for brain ischemia with a more suitable therapeutic window.

P2X7 Receptor-Dependent Layer-Specific Changes in Neuron-Microglia Reactivity in the Prefrontal Cortex of a Phencyclidine Induced Mouse Model of Schizophrenia.

Background: It has been consistently reported that the deficiency of the adenosine triphosphate (ATP) sensitive purinergic receptor P2X7 (P2X7R) ameliorates symptoms in animal models of brain diseases.Objective: This study aimed to investigate the role of P2X7R in rodent models of acute and subchronic schizophrenia based on phencyclidine (PCP) delivery in animals lacking or overexpressing P2X7R, and to identify the underlying mechanisms involved.Methods: The psychotomimetic effects of acute i.p. PCP administration in C57Bl/6J wild-type, P2X7R knockout (P2rx7−/−) and overexpressing (P2X7-EGFP) young adult mice were quantified. The medial prefrontal cortex (mPFC) of P2rx7−/− and heterozygous P2X7-EGFP acutely treated animals was characterized through immunohistochemical staining. The prefrontal cortices of young adult P2rx7−/− and P2rx7tg/+ mice were examined with tritiated dopamine release experiments and the functional properties of the mPFC pyramidal neurons in layer V from P2rx7−/− mice were assessed by patch-clamp recordings. P2rx7−/− animals were subjected to a 7 days subchronic systemic PCP treatment. The animals working memory performance and PFC cytokine levels were assessed.Results: Our data strengthen the hypothesis that P2X7R modulates schizophrenia-like positive and cognitive symptoms in NMDA receptor antagonist models in a receptor expression level-dependent manner. P2X7R expression leads to higher medial PFC susceptibility to PCP-induced circuit hyperactivity. The mPFC of P2X7R knockout animals displayed distinct alterations in the neuronal activation pattern, microglial organization, specifically around hyperactive neurons, and were associated with lower intrinsic excitability of mPFC neurons.Conclusions: P2X7R expression exacerbated PCP-related effects in C57Bl/6J mice. Our findings suggest a pleiotropic role of P2X7R in the mPFC, consistent with the observed behavioral phenotype, regulating basal dopamine concentration, layer-specific neuronal activation, intrinsic excitability of neurons in the mPFC, and the interaction of microglia with hyperactive neurons. Direct measurements of P2X7R activity concerning microglial ramifications and dynamics could help to further elucidate the molecular mechanisms involved.

Crosstalk Between Kappa Opioid and Dopamine Systems in Compulsive Behaviors.

The strength of goal-oriented behaviors is regulated by midbrain dopamine neurons. Dysfunctions of dopaminergic circuits are observed in drug addiction and obsessive-compulsive disorder. Compulsive behavior is a feature that both disorders share, which is associated to a heightened dopamine neurotransmission. The activity of midbrain dopamine neurons is principally regulated by the homeostatic action of dopamine through D2 receptors (D2R) that decrease the firing of neurons as well as dopamine synthesis and release. Dopamine transmission is also regulated by heterologous neurotransmitter systems such as the kappa opioid system, among others. Much of our current knowledge of the kappa opioid system and its influence on dopamine transmission comes from preclinical animal models of brain diseases. In 1988, using cerebral microdialysis, it was shown that the acute activation of the Kappa Opioid Receptors (KOR) decreases synaptic levels of dopamine in the striatum. This inhibitory effect of KOR opposes to the facilitating influence of drugs of abuse on dopamine release, leading to the proposition of the use of KOR agonists as pharmacological therapy for compulsive drug intake. Surprisingly, 30 years later, KOR antagonists are instead proposed to treat drug addiction. What may have happened during these years that generated this drastic change of paradigm? The collected evidence suggested that the effect of KOR on synaptic dopamine levels is complex, depending on the frequency of KOR activation and timing with other incoming stimuli to dopamine neurons, as well as sex and species differences. Conversely to its acute effect, chronic KOR activation seems to facilitate dopamine neurotransmission and dopamine-mediated behaviors. The opposing actions exerted by acute versus chronic KOR activation have been associated with an initial aversive and a delayed rewarding effect, during the exposure to drugs of abuse. Compulsive behaviors induced by repeated activation of D2R are also potentiated by the sustained co-activation of KOR, which correlates with decreased synaptic levels of dopamine and sensitized D2R. Thus, the time-dependent activation of KOR impacts directly on dopamine levels affecting the tuning of motivated behaviors. This review analyzes the contribution of the kappa opioid system to the dopaminergic correlates of compulsive behaviors.

Optimization and validation of online column-switching assisted HPLC-spectrometric method for quantification of dansylated endocannabinoids and neurotransmitters in animal models of brain diseases

In scientific research, animal modelling of human disease is pivotal in both studying the mechanisms of the disease and developing potential therapies. An imbalance in the interaction between the endocannabinoid (eCB) and Neurotransmitter (NT) systems may play a role in the pathogenesis of neurological diseases, such as Parkinson’s Disease (PD). The major limitation of current neurochemical practice is that different assays are used to measure each class of NTs.

Brain Redox Imaging Using In Vivo Electron Paramagnetic Resonance Imaging and Nitroxide Imaging Probes

Reactive oxygen species (ROS) are produced by living organisms as a result of normal cellular metabolism. Under normal physiological conditions, oxidative damage is prevented by the regulation of ROS by the antioxidant network. However, increased ROS and decreased antioxidant defense may contribute to many brain disorders, such as stroke, Parkinson’s disease, and Alzheimer’s disease. Noninvasive assessment of brain redox status is necessary for monitoring the disease state and the oxidative damage. Continuous-wave electron paramagnetic resonance (CW-EPR) imaging using redox-sensitive imaging probes, such as nitroxides, is a powerful method for visualizing the redox status modulated by oxidative stress in vivo. For conventional CW-EPR imaging, however, poor signal-to-noise ratio, low acquisition efficiency, and lack of anatomic visualization limit its ability to achieve three-dimensional redox mapping of small rodent brains. In this review, we discuss the instrumentation and coregistration of EPR images to anatomical images and appropriate nitroxide imaging probes, all of which are needed for a sophisticated in vivo EPR imager for all rodents. Using new EPR imaging systems, site-specific distribution and kinetics of nitroxide imaging probes in rodent brains can be obtained more accurately, compared to previous EPR imaging systems. We also describe the redox imaging studies of animal models of brain disease using newly developed EPR imaging.

Imaging of Neuronal Activity in Awake Mice by Measurements of Flavoprotein Autofluorescence Corrected for Cerebral Blood Flow.

Green fluorescence imaging (e.g., flavoprotein autofluorescence imaging, FAI) can be used to measure neuronal activity and oxygen metabolism in living brains without expressing fluorescence proteins. It is useful for understanding the mechanism of various brain functions and their abnormalities in age-related brain diseases. However, hemoglobin in cerebral blood vessels absorbs green fluorescence, hampering accurate assessments of brain function in animal models with cerebral blood vessel dysfunctions and subsequent cerebral blood flow (CBF) alterations. In the present study, we developed a new method to correct FAI signals for hemoglobin-dependent green fluorescence reductions by simultaneous measurements of green fluorescence and intrinsic optical signals. Intrinsic optical imaging enabled evaluations of light absorption and scatters by hemoglobin, which could then be applied to corrections of green fluorescence intensities. Using this method, enhanced flavoprotein autofluorescence by sensory stimuli was successfully detected in the brains of awake mice, despite increases of CBF, and hemoglobin interference. Moreover, flavoprotein autofluorescence could be properly quantified in a resting state and during sensory stimulation by a CO2 inhalation challenge, which modified vascular responses without overtly affecting neuronal activities. The flavoprotein autofluorescence signal data obtained here were in good agreement with the previous findings from a condition with drug-induced blockade of cerebral vasodilation, justifying the current assaying methodology. Application of this technology to studies on animal models of brain diseases with possible changes of CBF, including age-related neurological disorders, would provide better understanding of the mechanisms of neurovascular coupling in pathological circumstances.

Kinetics and metabolism of apocynin in the mouse brain assessed with positron-emission tomography

BackgroundApocynin is a constituent of the medicinal herb Picrorhiza kurroa. It is an inhibitor of nicotinamide adenine dinucleotide phosphate oxidase. This compound shows potential anti-inflammatory and antioxidant effects and has been tested as a neuroprotectant in many animal models of brain disease. In such studies, understanding the brain kinetics of apocynin would be important for interpreting its in vivo efficacy; however, little has been reported on the kinetics of apocynin in the brain. PurposeThe purpose of this study is to investigate the kinetics and metabolism of apocynin in the brain of mice. Study designThe kinetics and metabolism of apocynin were examined using [11C]apocynin and positron-emission tomography (PET). MethodsIn vivo PET scanning was performed in mice for 20min after intraperitoneal administration of an apocynin solution containing [11C]apocynin. Metabolites in the brain were analyzed using high-performance liquid chromatography. The doses of apocynin used ranged from <1.5 µg/kg (tracer dose) to 100mg/kg. ResultsBrain radioactivity during the period of 0 to 20min after administration was negligible at the tracer dose and extremely low at the dose of 10mg/kg. Moderate radioactivity was observed in the brain a few minutes after administration at the doses of 25 and 50mg/kg and rapidly decreased thereafter. At a dose of 100mg/kg, [11C]apocynin resulted in a high uptake of radioactivity followed by a gradual washout. In contrast to the brain, a clear dose-dependent increase in radioactivity was not observed in the blood. The fraction of the unchanged form in the brain decreased with time, and the degree of the reduction depended on apocynin doses: apocynin was rapidly metabolized in the brain at lower doses, whereas it was slowly decomposed at higher doses. On the basis of these data, the maximum apocynin concentrations in the brain were calculated to be 10 µM (10mg/kg), 49 µM (25mg/kg), 150 µM (50mg/kg), and 380 µM (100mg/kg). A metabolite observed in the brain was found to be apocynin glucuronide but not diapocynin, an active metabolite. ConclusionThese results would be useful for an evaluation of the potential efficacy of apocynin as a neuroprotective agent.

The Role of mPGES-1 in Inflammatory Brain Diseases.

Prostaglandin E2 (PGE2) has been thought to be an important mediator of inflammation in peripheral tissues, but recent studies clearly show the involvement of PGE2 in inflammatory brain diseases. In some animal models of brain disease, the genetic disruption and chemical inhibition of cyclooxygenase (COX)-2 resulted in the reduction of PGE2 and amelioration of symptoms, and it had been thought that PGE2 produced by COX-2 may be involved in the progression of injuries. However, COX-2 produces not only PGE2, but also some other prostanoids, and thus the protective effects of COX-2 inhibition, as well as severe side effects, may be caused by the inhibition of prostanoids other than PGE2. Therefore, to elucidate the role of PGE2, studies of microsomal prostaglandin E synthase-1 (mPGES-1), an inducible terminal enzyme for PGE2 synthesis, have recently been an active area of research. Studies from mPGES-1 deficient mice provide compelling evidence for its role in a variety of inflammatory brain diseases, such as ischemic stroke, Alzheimer's disease and epilepsy, and clues for developing new therapeutic treatments for brain diseases by targeting mPGES-1. Considering that COX inhibitors may non-selectively suppress the production of many types of prostanoids that are essential for normal physiological functioning of the brain and peripheral tissues, as well as induce gastro-intestinal, renal and cardiovascular complications, mPGES-1 inhibitors are expected to be injury-selective and have fewer side-effects when treating human brain diseases. Thus, this paper focuses on recent studies that have demonstrated the involvement of mPGES-1 in pathological brain diseases.

High-throughput 3D whole-brain quantitative histopathology in rodents.

Histology is the gold standard to unveil microscopic brain structures and pathological alterations in humans and animal models of disease. However, due to tedious manual interventions, quantification of histopathological markers is classically performed on a few tissue sections, thus restricting measurements to limited portions of the brain. Recently developed 3D microscopic imaging techniques have allowed in-depth study of neuroanatomy. However, quantitative methods are still lacking for whole-brain analysis of cellular and pathological markers. Here, we propose a ready-to-use, automated, and scalable method to thoroughly quantify histopathological markers in 3D in rodent whole brains. It relies on block-face photography, serial histology and 3D-HAPi (Three Dimensional Histology Analysis Pipeline), an open source image analysis software. We illustrate our method in studies involving mouse models of Alzheimer’s disease and show that it can be broadly applied to characterize animal models of brain diseases, to evaluate therapeutic interventions, to anatomically correlate cellular and pathological markers throughout the entire brain and to validate in vivo imaging techniques.

Non-Human Primate: An Essential Building Brick in the Discovery of the Subthalamic Deep Brain Stimulation Therapy.

Non-Human Primate: An Essential Building Brick in the Discovery of the Subthalamic Deep Brain Stimulation Therapy.

Expression of angiotensinogen and receptors for angiotensin and prorenin in the monkey and human substantia nigra: an intracellular renin–angiotensin system in the nigra

We have previously obtained in rodents a considerable amount of data suggesting a major role for the brain renin–angiotensin system (RAS) in dopaminergic neuron degeneration and potentially in Parkinson’s disease. However, the presence of a local RAS has not been demonstrated in the monkey or the human substantia nigra compacta (SNc). The present study demonstrates the presence of major RAS components in dopaminergic neurons, astrocytes and microglia in both the monkey and the human SNc. Angiotensin type 1 and 2 and renin–prorenin receptors were located at the surface of dopaminergic neurons and glial cells, as expected for a tissular RAS. However, angiotensinogen and receptors for angiotensin and renin–prorenin were also observed at the cytoplasm and nuclear level, which suggests the presence of an intracrine or intracellular RAS in monkey and human SNc. Although astrocytes and microglia were labeled for angiotensin and prorenin receptors in the normal SNc, most glial cells appeared less immunoreactive than the dopaminergic neurons. However, our previous studies in rodent models of PD and studies in other animal models of brain diseases suggest that the RAS activity is significantly upregulated in glial cells in pathological conditions. The present results together with our previous findings in rodents suggest a major role for the nigral RAS in the normal functioning of the dopaminergic neurons, and in the progression of the dopaminergic degeneration.

Passages 2012

Passages 2012

Diffusion tensor MRI with tract-based spatial statistics and histology reveals undiscovered lesioned areas in kainate model of epilepsy in rat

In this study, we used tract-based spatial statistics (TBSS) to analyze diffusion tensor MR imaging (DTI) data acquired from the rat brain, ex vivo, for the first time. The aim was to highlight potential changes in the whole brain anatomy in the kainic acid model of epilepsy, and further characterize the changes with histology. Increased FA was observed in dorsal endopiriform nucleus, external capsule, corpus callosum, dentate gyrus, thalamus, and optic tract. A decrease in FA was seen in the horizontal limb of the diagonal band, stria medullaris, habenula, entorhinal cortex, and superior colliculus. Some of the areas have been described in kainic acid model before. However, we also found regions that to our knowledge have not been previously reported to undergo structural changes, in this model, including stria medullaris, nucleus of diagonal band, habenula, superior colliculus, external capsule, corpus callosum, and optic tract. Four of the areas highlighted in TBSS (dentate gyrus, entorhinal cortex, thalamus and stria medullaris) were analyzed in more detail with Nissl, Timm, and myelin-stained histological sections, and with polarized light microscopy. TBSS together with targeted histology confirmed that DTI changes were associated with altered myelination, neurodegeneration, and/or calcification of the tissue. Our data demonstrate that DTI in combination with TBSS has a great potential to facilitate the discovery of previously undetected anatomical changes in animal models of brain diseases.

Intranasal Phosphoramidon Increases Beta-Amyloid Levels in Wild-Type and NEP/NEP2-Deficient Mice

Intranasal administration is emerging as a reliable and non-invasive method to bypass the blood-brain barrier and deliver drugs to the brain. This approach has been primarily used to explore therapeutic avenues for neurological diseases. However, intranasal administration could also be used to create animal models of brain disease. Beta-amyloid peptide (Aβ) accumulation is a key feature of Alzheimer's disease (AD), and the most common models of AD are transgenic mice expressing mutant human genes linked to familial AD. An alternative model of amyloidosis utilizes intracerebroventricular infusion of thiorphan or phosphoramidon to block the activity of key Aβ degrading enzymes (NEP, NEP2) resulting in accumulation of Aβ. Here, we demonstrate that intranasal administration of phosphoramidon produces significantly elevated cerebral Aβ levels in wild-type mice. Furthermore, intranasal phosphoramidon administration in double knockout mice lacking NEP and NEP2 also showed increased levels of Aβ(40). These data show that intranasal delivery of drugs can be used to model AD and suggest that other phosphoramidon-sensitive peptidases are degrading Aβ in NEP/NEP2-deficient mice.

Functional multineuron calcium imaging for systems pharmacology

Functional multineuron calcium imaging (fMCI) is a large-scale technique used to access brain function on a single-neuron scale. It detects the activity of individual neurons by imaging action potential-evoked transient calcium influxes into their cell bodies. fMCI has recently been used as a high-throughput research tool to examine how neuronal activity is altered in animal models of brain diseases, for example stroke, Alzheimer's disease, and epilepsy, and to estimate how pharmacological agents act on normal and abnormal states of neuronal networks. It offers unique opportunities to discover the mechanisms underlying neurological disorders and new therapeutic targets.

Neuroanatomical tracing combined with in situ hybridization: Analysis of gene expression patterns within brain circuits of interest

Most of our current understanding of brain circuits is based on hodological studies carried out using neuroanatomical tract-tracing. Our aim is to advance one step further by visualizing the functional correlate in a given circuit. In this regard, we believe it is feasible to combine retrograde tracing with fluorescence, non-radioactive in situ hybridization (ISH) protocols. The subsequent detection at the single-cell level of the expression of a given mRNA within retrograde-labeled neurons provides information regarding cellular function. This may be of particular interest when trying to elucidate the performance of brain circuits of interest in animal models of brain diseases. Several combinations of retrograde tracing with either single- and double-ISH are presented here, together with some criteria that influence the selection of the tracer to be used in conjunction with the strong demands of the ISH.

Synthesis and Biological Evaluation of Amidine, Guanidine, and Thiourea Derivatives of 2-Amino(6-trifluoromethoxy)benzothiazole as Neuroprotective Agents Potentially Useful in Brain Diseases

A series of amidine, thiourea, and guanidine derivatives of 2-amino-6-(trifluoromethoxy)benzothiazole termed 2, 3, and 4, respectively, and structurally related to riluzole, a neuroprotective drug in many animal models of brain disease, have been synthesized. The biological activity of compounds 2a-e, 3a-f, and 4a,b was preliminarily tested by means of an in vitro protocol of ischemia/reperfusion injury. The results demonstrated that 2c and 3a-d significantly attenuated neuronal injury. Selected for testing of their antioxidant properties, compounds 3a-d were shown to be endowed with a direct ROS scavenging activity. Compounds 3b and 3d were also evaluated for their activity on voltage-dependent Na(+) and Ca(2+) currents in neurons from rat piriform cortex. At 50 microM, compound 3b inhibited the transient Na(+) current to a much smaller extent than riluzole, whereas 3d was almost completely ineffective.