Persistence of learning-induced synapses depends on neurotrophic priming of glucocorticoid receptors.

Stress can either promote or impair learning and memory. Such opposing effects depend on whether synapses persist or decay after learning. Maintenance of new synapses formed at the time of learning upon neuronal network activation depends on the stress hormone-activated glucocorticoid receptor (GR) and neurotrophic factor release. Whether and how concurrent GR and neurotrophin signaling integrate to modulate synaptic plasticity and learning is not fully understood. Here, we show that deletion of the neurotrophin brain-derived neurotrophic factor (BDNF)-dependent GR-phosphorylation (PO4) sites impairs long-term memory retention and maintenance of newly formed postsynaptic dendritic spines in the mouse cortex after motor skills training. Chronic stress and the BDNF polymorphism Val66Met disrupt the BDNF-dependent GR-PO4 pathway necessary for preserving training-induced spines and previously acquired memories. Conversely, enrichment living promotes spine formation but fails to salvage training-related spines in mice lacking BDNF-dependent GR-PO4 sites, suggesting it is essential for spine consolidation and memory retention. Mechanistically, spine maturation and persistence in the motor cortex depend on synaptic mobilization of the glutamate receptor subunit A1 (GluA1) mediated by GR-PO4 Together, these findings indicate that regulation of GR-PO4 via activity-dependent BDNF signaling is important for the formation and maintenance of learning-dependent synapses. They also define a signaling mechanism underlying these effects.

Experience and activity-dependent control of glucocorticoid receptors during the stress response in large-scale brain networks.

The diversity of actions of the glucocorticoid stress hormones among individuals and within organs, tissues and cells is shaped by age, gender, genetics, metabolism, and the quantity of exposure. However, such factors cannot explain the heterogeneity of responses in the brain within cells of the same lineage, or similar tissue environment, or in the same individual. Here, we argue that the stress response is continuously updated by synchronized neural activity on large-scale brain networks. This occurs at the molecular, cellular and behavioral levels by crosstalk communication between activity-dependent and glucocorticoid signaling pathways, which updates the diversity of responses based on prior experience. Such a Bayesian process determines adaptation to the demands of the body and external world. We propose a framework for understanding how the diversity of glucocorticoid actions throughout brain networks is essential for supporting optimal health, while its disruption may contribute to the pathophysiology of stress-related disorders, such as major depression, and resistance to therapeutic treatments.

The Stress-Induced Transcription Factor NR4A1 Adjusts Mitochondrial Function and Synapse Number in Prefrontal Cortex.

The energetic costs of behavioral chronic stress are unlikely to be sustainable without neuronal plasticity. Mitochondria have the capacity to handle synaptic activity up to a limit before energetic depletion occurs. Protective mechanisms driven by the induction of neuronal genes likely evolved to buffer the consequences of chronic stress on excitatory neurons in prefrontal cortex (PFC), as this circuitry is vulnerable to excitotoxic insults. Little is known about the genes involved in mitochondrial adaptation to the buildup of chronic stress. Using combinations of genetic manipulations and stress for analyzing structural, transcriptional, mitochondrial, and behavioral outcomes, we characterized NR4A1 as a stress-inducible modifier of mitochondrial energetic competence and dendritic spine number in PFC. NR4A1 acted as a transcription factor for changing the expression of target genes previously involved in mitochondrial uncoupling, AMP-activated protein kinase activation, and synaptic growth. Maintenance of NR4A1 activity by chronic stress played a critical role in the regressive synaptic organization in PFC of mouse models of stress (male only). Knockdown, dominant-negative approach, and knockout of Nr4a1 in mice and rats (male only) protected pyramidal neurons against the adverse effects of chronic stress. In human PFC tissues of men and women, high levels of the transcriptionally active NR4A1 correlated with measures of synaptic loss and cognitive impairment. In the context of chronic stress, prolonged expression and activity of NR4A1 may lead to responses of mitochondria and synaptic connectivity that do not match environmental demand, resulting in circuit malfunction between PFC and other brain regions, constituting a pathological feature across disorders.SIGNIFICANCE STATEMENT The bioenergetic cost of chronic stress is too high to be sustainable by pyramidal prefrontal neurons. Cellular checkpoints have evolved to adjust the responses of mitochondria and synapses to the buildup of chronic stress. NR4A1 plays such a role by controlling the energetic competence of mitochondria with respect to synapse number. As an immediate-early gene, Nr4a1 promotes neuronal plasticity, but sustained expression or activity can be detrimental. NR4A1 expression and activity is sustained by chronic stress in animal models and in human studies of neuropathologies sensitive to the buildup of chronic stress. Therefore, antagonism of NR4A1 is a promising avenue for preventing the regressive synaptic reorganization in cortical systems in the context of chronic stress.

Gene therapy blockade of dorsal striatal p11 improves motor function and dyskinesia in parkinsonian mice.

Complications of dopamine replacement for Parkinson's disease (PD) can limit therapeutic options, leading to interest in identifying novel pathways that can be exploited to improve treatment. p11 (S100A10) is a cellular scaffold protein that binds to and potentiates the activity of various ion channels and neurotransmitter receptors. We have previously reported that p11 can influence ventral striatal function in models of depression and drug addiction, and thus we hypothesized that dorsal striatal p11 might mediate motor function and drug responses in parkinsonian mice. To focally inhibit p11 expression in the dorsal striatum, we injected an adeno-associated virus (AAV) vector producing a short hairpin RNA (AAV.sh.p11). This intervention reduced the impairment in motor function on forced tasks, such as rotarod and treadmill tests, caused by substantia nigra lesioning in mice. Measures of spontaneous movement and gait in an open-field test declined as expected in control lesioned mice, whereas AAV.sh.p11 mice remained at or near normal baseline. Mice with unilateral lesions were then challenged with l-dopa (levodopa) and various dopamine receptor agonists, and resulting rotational behaviors were significantly reduced after ipsilateral inhibition of dorsal striatal p11 expression. Finally, p11 knockdown in the dorsal striatum dramatically reduced l-dopa-induced abnormal involuntary movements compared with control mice. These data indicate that focal inhibition of p11 action in the dorsal striatum could be a promising PD therapeutic target to improve motor function while reducing l-dopa-induced dyskinesias.

Neurotrophic-priming of glucocorticoid receptor signaling is essential for neuronal plasticity to stress and antidepressant treatment.

Neurotrophins and glucocorticoids are robust synaptic modifiers, and deregulation of their activities is a risk factor for developing stress-related disorders. Low levels of brain-derived neurotrophic factor (BDNF) increase the desensitization of glucocorticoid receptors (GR) and vulnerability to stress, whereas higher levels of BDNF facilitate GR-mediated signaling and the response to antidepressants. However, the molecular mechanism underlying neurotrophic-priming of GR function is poorly understood. Here we provide evidence that activation of a TrkB-MAPK pathway, when paired with the deactivation of a GR-protein phosphatase 5 pathway, resulted in sustained GR phosphorylation at BDNF-sensitive sites that is essential for the transcription of neuronal plasticity genes. Genetic strategies that disrupted GR phosphorylation or TrkB signaling in vivo impaired the neuroplasticity to chronic stress and the effects of the antidepressant fluoxetine. Our findings reveal that the coordinated actions of BDNF and glucocorticoids promote neuronal plasticity and that disruption in either pathway could set the stage for the development of stress-induced psychiatric diseases.

Cerebrovascular pathology during the progression of experimental Alzheimer's disease.

Clinical and experimental evidence point to a possible role of cerebrovascular dysfunction in Alzheimer's disease (AD). The 5xFAD mouse model of AD expresses human amyloid precursor protein and presenilin genes with mutations found in AD patients. It remains unknown whether amyloid deposition driven by these mutations is associated with cerebrovascular changes. 5xFAD and wild type mice (2 to 12months old; M2 to M12) were used. Thinned skull in vivo 2-photon microscopy was used to determine Aß accumulation on leptomeningeal or superficial cortical vessels over time. Parenchymal microvascular damage was assessed using FITC-microangiography. Collagen-IV and CD31 were used to stain basal lamina and endothelial cells. Methoxy-XO4, Thioflavin-S or 6E10 were used to visualize Aß accumulation in living mice or in fixed brain tissues. Positioning of reactive IBA1 microglia and GFAP astrocytes at the vasculature was rendered using confocal microscopy. Platelet-derived growth factor receptor beta (PDGFRß) staining was used to visualize perivascular pericytes. In vivo 2-photon microscopy revealed Methoxy-XO4(+) amyloid perivascular deposits on leptomeningeal and penetrating cortical vessels in 5xFAD mice, typical of cerebral amyloid angiopathy (CAA). Amyloid deposits were visible in vivo at M3 and aggravated over time. Progressive microvascular damage was concomitant to parenchymal Aß plaque accumulation in 5xFAD mice. Microvascular inflammation in 5xFAD mice presented with sporadic FITC-albumin leakages at M4 becoming more prevalent at M9 and M12. 3D colocalization showed inflammatory IBA1(+) microglia proximal to microvascular FITC-albumin leaks. The number of perivascular PDGFRß(+) pericytes was significantly decreased at M4 in the fronto-parietal cortices, with a trend decrease observed in the other structures. At M9-M12, PDGFRß(+) pericytes displayed hypertrophic perivascular ramifications contiguous to reactive microglia. Cerebral amyloid angiopathy and microvascular inflammation occur in 5xFAD mice concomitantly to parenchymal plaque deposition. The prospect of cerebrovascular pharmacology in AD is discussed.

Timing and crosstalk of glucocorticoid signaling with cytokines, neurotransmitters and growth factors.

Glucocorticoid actions are tailored to the organs and cells responding thanks to complex integration with ongoing signaling mediated by cytokines, hormones, neurotransmitters, and growth factors. Disruption of: (1) the amount of signaling molecules available locally; (2) the timing with other signaling pathways; (3) the post-translational modifications on glucocorticoid receptors; and (4) the receptors-interacting proteins within cellular organelles and functional compartments, can modify the sensitivity and efficacy of glucocorticoid responses with implications in physiology, diseases and treatments. Tissue sensitivity to glucocorticoids is sustained by multiple systems that do not operate in isolation. We take the example of the interplay between the glucocorticoid and brain-derived neurotrophic factor signaling pathways to deconstruct context-dependent glucocorticoid responses that play key roles in physiology, diseases and therapies.

Linking Mitochondria to Synapses: New Insights for Stress-Related Neuropsychiatric Disorders.

The brain evolved cellular mechanisms for adapting synaptic function to energy supply. This is particularly evident when homeostasis is challenged by stress. Signaling loops between the mitochondria and synapses scale neuronal connectivity with bioenergetics capacity. A biphasic "inverted U shape" response to the stress hormone glucocorticoids is demonstrated in mitochondria and at synapses, modulating neural plasticity and physiological responses. Low dose enhances neurotransmission, synaptic growth, mitochondrial functions, learning, and memory whereas chronic, higher doses produce inhibition of these functions. The range of physiological effects by stress and glucocorticoid depends on the dose, duration, and context at exposure. These criteria are met by neuronal activity and the circadian, stress-sensitive and ultradian, stress-insensitive modes of glucocorticoid secretion. A major hallmark of stress-related neuropsychiatric disorders is the disrupted glucocorticoid rhythms and tissue resistance to signaling with the glucocorticoid receptor (GR). GR resistance could result from the loss of context-dependent glucocorticoid signaling mediated by the downregulation of the activity-dependent neurotrophin BDNF. The coincidence of BDNF and GR signaling changes glucocorticoid signaling output with consequences on mitochondrial respiration efficiency, synaptic plasticity, and adaptive trajectories.

Molecular Biology of Glucocorticoid Signaling.

Well-defined as signaling hormones for the programming of cell type-specific and context-dependent gene expression signatures, glucocorticoids control experience-driven allostasis. One unifying model is that glucocorticoids help maintaining the integrity and plasticity of cellular networks in changing environments through the mobilization of cellular energy stores, profiling of gene expression, and changes in the electrical and morphological properties of cells. The nucleus is their primary site of action, yet recent discoveries point to additional gene transcription-independent functions at the plasma membrane of neuronal synapses. Glucocorticoids are secreted factors that reflect intrinsically the changes coming from the external world, temporally and regionally, during development and adulthood. In this review, we will enumerate the properties and signaling attributes of glucocorticoids and their receptors that characterize them as allostatic modulators. The molecular mechanisms used to support their role at the synapse will be highlighted.

Cholinergic interneurons in the nucleus accumbens regulate depression-like behavior.

A large number of studies have demonstrated that the nucleus accumbens (NAC) is a critical site in the neuronal circuits controlling reward responses, motivation, and mood, but the neuronal cell type(s) underlying these processes are not yet known. Identification of the neuronal cell types that regulate depression-like states will guide us in understanding the biological basis of mood and its regulation by diseases like major depressive disorder. Taking advantage of recent findings demonstrating that the serotonin receptor chaperone, p11, is an important molecular regulator of depression-like states, here we identify cholinergic interneurons (CINs) as a primary site of action for p11 in the NAC. Depression-like behavior is observed in mice after decrease of p11 levels in NAC CINs. This phenotype is recapitulated by silencing neuronal transmission in these cells, demonstrating that accumbal cholinergic neuronal activity regulates depression-like behaviors and suggesting that accumbal CIN activity is crucial for the regulation of mood and motivation.

[Depression and addiction comorbidity: towards a common molecular target?]. / Comorbidité entre la dépression et l'addiction - Vers une cible moléculaire commune ?

The comorbidity of depression and cocaine addiction suggests shared mechanisms and anatomical pathways. Specifically, the limbic structures, such as the nucleus accumbens (NAc), play a crucial role in both disorders. P11 (S100A10) is a promising target for manipulating depression and addiction in mice. We summarized the recent genetic and viral strategies used to determine how the titration of p11 levels within the NAc affects hedonic behavior and cocaine reward learning in mice. In particular, p11 in the ChAT+ cells or DRD1+ MSN of the NAc, controls depressive-like behavior or cocaine reward, respectively. Treatments to counter maladaptation of p11 levels in the NAc could provide novel therapeutic opportunities for depression and cocaine addiction in humans.

Loss of glucocorticoid receptor phosphorylation contributes to cognitive and neurocentric damages of the amyloid-ß pathway.

Aberrant cortisol and activation of the glucocorticoid receptor (GR) play an essential role in age-related progression of Alzheimer's disease (AD). However, the GR pathways required for influencing the pathobiology of AD dementia remain unknown. To address this, we studied an early phase of AD-like progression in the well-established APP/PS1 mouse model combined with targeted mutations in the BDNF-dependent GR phosphorylation sites (serines 134/267) using molecular, behavioral and neuroimaging approaches. We found that disrupting GR phosphorylation (S134A/S267A) in mice exacerbated the deleterious effects of the APP/PS1 genotype on mortality, neuroplasticity and cognition, without affecting either amyloid-ß deposition or vascular pathology. The dynamics, maturation and retention of task-induced new dendritic spines of cortical excitatory neurons required GR phosphorylation at the BDNF-dependent sites that amyloid-ß compromised. Parallel studies in postmortem human prefrontal cortex revealed AD subjects had downregulated BDNF signaling and concomitant upregulated cortisol pathway activation, which correlated with cognitive decline. These results provide key evidence that the loss of neurotrophin-mediated GR phosphorylation pathway promotes the detrimental effects of the brain cortisol response that contributes to the onset and/or progression of AD dementia. These findings have important translational implications as they provide a novel approach to treating AD dementia by identifying drugs that increase GR phosphorylation selectively at the neurotrophic sites to improve memory and cognition.

Cerebellar dopamine D2 receptors regulate social behaviors.

The cerebellum, a primary brain structure involved in the control of sensorimotor tasks, also contributes to higher cognitive functions including reward, emotion and social interaction. Although the regulation of these behaviors has been largely ascribed to the monoaminergic system in limbic regions, the contribution of cerebellar dopamine signaling in the modulation of these functions remains largely unknown. By combining cell-type-specific transcriptomics, histological analyses, three-dimensional imaging and patch-clamp recordings, we demonstrate that cerebellar dopamine D2 receptors (D2Rs) in mice are preferentially expressed in Purkinje cells (PCs) and regulate synaptic efficacy onto PCs. Moreover, we found that changes in D2R levels in PCs of male mice during adulthood alter sociability and preference for social novelty without affecting motor functions. Altogether, these findings demonstrate novel roles for D2R in PC function and causally link cerebellar D2R levels of expression to social behaviors.

Optimization of glioblastoma multiforme stem cell isolation, transfection, and transduction.

It has been postulated that brain tumor stem cells (TSCs) may be the population of cells responsible for the maintenance and recurrence of glioblastoma multiforme (GBM). The purpose of this study was to optimize a reproducible protocol for generating TSCs for their subsequent transfection or transduction. Patient GBMs were enzymatically and mechanically dissociated and tumor spheres were resuspended in appropriate media and analyzed to ensure they met stem cell criteria. These cells were then transfected with a plasmid or transduced with a viral vector to introduce a previously absent gene and then allowed to form tumor spheres. Tumor spheres were generated from patient GBMs without contamination. These cells met stringent criteria as stem cells, including multipotentiality and self-renewal. High efficiency transfection and transduction of tumor spheres was possible, even at the core of the sphere. This allowed for the introduction of new genes to the TSCs, as evidenced by fluorescent microscopy and Western blot analysis. This study is a guide to optimize the generation of patient derived GBM tumor spheres without RBC and dead cell contamination. GBM TSCs within tumor spheres can easily be transfected with plasmids or transduced with a virus. This is important from a therapeutic perspective if gene replacement is to be successful in replacing genes lost in GBM progression or to knock down or silence genes that are over-expressed in malignant brain tumors.

Dual imaging of dendritic spines and mitochondria in vivo reveals hotspots of plasticity and metabolic adaptation to stress.

Metabolic adaptation is a critical feature of synaptic plasticity. Indeed, synaptic plasticity requires the utilization and resupply of metabolites, in particular when the turnover is high and fast such as in stress conditions. What accounts for the localized energy burden of the post-synaptic compartment to the build up of chronic stress is currently not understood. We used in vivo microscopy of genetically encoded fluorescent probes to track changes of mitochondria, dendritic spines, ATP and H2O2 levels in pyramidal neurons of cortex before and after chronic unpredictable mild stress. Data revealed hotspots of postsynaptic mitochondria and dendritic spine turnover. Pharmacogenetic approach to force expression of the metabolic stress gene NR4A1 caused the fragmentation of postsynaptic mitochondria and loss of proximal dendritic spine clusters, whereas a dominant-negative mutant counteracted the effect of chronic stress. When fragmented, dendritic mitochondria produced lesser ATP at resting state and more on acute demand. This corresponded with significant production of mitochondrial H2O2 oxidative species in the dendritic compartment. Together, data indicate that pyramidal neurons adjust proximal dendritic spine turnover and mitochondria functions in keeping with synaptic demands.

Regeneration of the neurogliovascular unit visualized in vivo by transcranial live-cell imaging.

Functional imaging in behaving animals is essential to explore brain functions. Real-time optical imaging of brain functions is limited by light scattering, skull distortion, timing resolution and subcellular precision that altogether, make challenging the rapid acquisition of uncorrupted functional data of cells integrated de novo in the neurogliovascular unit. We report multimodal transcranial in vivo optical imaging for the fast and direct visualization of microcirculation in the perfusion domain where new cells incorporated in the neurogliovascular unit during the progression of a seizure disorder and its treatment. Using this methodology, we explored the performance improvement of cells integrated de novo in the neurogliovascular unit. We report fast transcranial imaging of blood microcirculation at sites of pericyte turnover in the epileptic brain and after treatment with a trophic factor that revealed key features of the regenerating neurogliovascular unit.

Fungicide Residues Exposure and ß-amyloid Aggregation in a Mouse Model of Alzheimer's Disease.

BACKGROUND: Pesticide residues have contaminated our environment and nutrition over the last century. Although these compounds are present at very low concentrations, their long-term effects on human health is of concern. The link between pesticide residues and Alzheimer's disease is not clear and difficult to establish. To date, no in vivo experiments have yet modeled the impact of this chronic contamination on neurodegenerative disorders. OBJECTIVES: We investigated the impact of fungicide residues on the pathological markers of Alzheimer's disease in a transgenic mouse model. METHODS: Transgenic (J20, hAPPSw/Ind) mice were chronically exposed to a cocktail of residues of cyprodinil, mepanipyrim, and pyrimethanil at 0.1µg/L in their drinking water for 9 months. We assessed the effects of fungicide residues on the pathological markers of the disease including Aß aggregates, neuroinflammation, and neuronal loss. Then, we studied the dynamics of Aß aggregation in vivo via a longitudinal study using two-photon microscopy. Finally, we investigated the molecular mechanisms involved in the production and clearance of Aß peptides. RESULTS: We found that a chronic exposure to three fungicide residues exacerbated aggregation, microgliosis, and neuronal loss. These fungicides also increased vascular amyloid aggregates reminiscent of cerebral amyloid angiopathy between 6 and 9 months of treatment. The mechanism of action revealed that fungicides promoted Aß peptide fibril formation in vitro and involved an in vivo overexpression of the levels of the ß-secretase-cleaving enzyme (BACE1) combined with impairment of Aß clearance through neprylisin (NEP). CONCLUSIONS: Chronic exposure of the J20 mouse model of Alzheimer's disease to a cocktail of fungicides, at the regulatory concentration allowed in tap water (0.1µg/L), strengthened the preexisting pathological markers: neuroinflammation, Aß aggregation, and APP ß-processing. We hypothesize prevention strategies toward pesticide long-term exposure may be an alternative to counterbalance the lack of treatment and to slow down the worldwide Alzheimer's epidemic. https://doi.org/10.1289/EHP5550.

Cav3.2 T-type calcium channels shape electrical firing in mouse Lamina II neurons.

The T-type calcium channel, Cav3.2, is necessary for acute pain perception, as well as mechanical and cold allodynia in mice. Being found throughout sensory pathways, from excitatory primary afferent neurons up to pain matrix structures, it is a promising target for analgesics. In our study, Cav3.2 was detected in ~60% of the lamina II (LII) neurons of the spinal cord, a site for integration of sensory processing. It was co-expressed with Tlx3 and Pax2, markers of excitatory and inhibitory interneurons, as well as nNOS, calretinin, calbindin, PKCγ and not parvalbumin. Non-selective T-type channel blockers slowed the inhibitory but not the excitatory transmission in LII neurons. Furthermore, T-type channel blockers modified the intrinsic properties of LII neurons, abolishing low-threshold activated currents, rebound depolarizations, and blunting excitability. The recording of Cav3.2-positive LII neurons, after intraspinal injection of AAV-DJ-Cav3.2-mcherry, showed that their intrinsic properties resembled those of the global population. However, Cav3.2 ablation in the dorsal horn of Cav3.2GFP-Flox KI mice after intraspinal injection of AAV-DJ-Cav3.2-Cre-IRES-mcherry, had drastic effects. Indeed, it (1) blunted the likelihood of transient firing patterns; (2) blunted the likelihood and the amplitude of rebound depolarizations, (3) eliminated action potential pairing, and (4) remodeled the kinetics of the action potentials. In contrast, the properties of Cav3.2-positive neurons were only marginally modified in Cav3.1 knockout mice. Overall, in addition to their previously established roles in the superficial spinal cord and in primary afferent neurons, Cav3.2 channel appear to be necessary for specific, significant and multiple controls of LII neuron excitability.

Topographic Reorganization of Cerebrovascular Mural Cells under Seizure Conditions.

Reorganization of the neurovascular unit has been suggested in the epileptic brain, although the dynamics and functional significance remain unclear. Here, we tracked the in vivo dynamics of perivascular mural cells as a function of electroencephalogram (EEG) activity following status epilepticus. We segmented the cortical vascular bed to provide a size- and type-specific analysis of mural cell plasticity topologically. We find that mural cells are added and removed from veins, arterioles, and capillaries after seizure induction. Loss of mural cells is proportional to seizure severity and vascular pathology (e.g., rigidity, perfusion, and permeability). Treatment with platelet-derived growth factor subunits BB (PDGF-BB) reduced mural cell loss, vascular pathology, and epileptiform EEG activity. We propose that perivascular mural cells play a pivotal role in seizures and are potential targets for reducing pathophysiology.

Longitudinal In Vivo Imaging of the Cerebrovasculature: Relevance to CNS Diseases.

Remodeling of the brain vasculature is a common trait of brain pathologies. In vivo imaging techniques are fundamental to detect cerebrovascular plasticity or damage occurring overtime and in relation to neuronal activity or blood flow. In vivo two-photon microscopy allows the study of the structural and functional plasticity of large cellular units in the living brain. In particular, the thinned-skull window preparation allows the visualization of cortical regions of interest (ROI) without inducing significant brain inflammation. Repetitive imaging sessions of cortical ROI are feasible, providing the characterization of disease hallmarks over time during the progression of numerous CNS diseases. This technique accessing the pial structures within 250 µm of the brain relies on the detection of fluorescent probes encoded by genetic cellular markers and/or vital dyes. The latter (e.g., fluorescent dextrans) are used to map the luminal compartment of cerebrovascular structures. Germane to the protocol described herein is the use of an in vivo marker of amyloid deposits, Methoxy-O4, to assess Alzheimer's disease (AD) progression. We also describe the post-acquisition image processing used to track vascular changes and amyloid depositions. While focusing presently on a model of AD, the described protocol is relevant to other CNS disorders where pathological cerebrovascular changes occur.