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Effects of inhaled anesthetic isoflurane on long-term potentiation of CA3 pyramidal cell afferents in vivo

Effects of inhaled anesthetic isoflurane on long-term potentiation of CA3 pyramidal cell afferents in vivo

and CA3 pyramidal cell dendrites both have glutamatergic synapses, it appears plausible that CA1 and CA3 dendrites may show some similar mechanisms under the influence of isoflurane anesthesia. However, there are several differences in the experimental protocol that could account for variance in the results of this experimentation. The current acute electrophysiological experimentation examines synaptic con- nections to CA3, which differ in several aspects from CA1, and while we examined the effects of control and inhibitory drugs to the afferents of CA3, the animal was under a surgi- cal dose of anesthesia.
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A Stereological Study on Hippocampal Subfields Following Administration of Methamphetamine in Male Mice

A Stereological Study on Hippocampal Subfields Following Administration of Methamphetamine in Male Mice

The main findings of this study by using the design-based stereological methods were: Subchronic administration of METH-induced significant volumetric change in the sublayers of the hippocampal CA1 and CA3 in adult male mice. Subchronic exposure to METH leads to alterations in numerical density and a total number of hippocampal CA1 and CA3 pyramidal neurons. Subchronic METH exposure induced changes in Golgi-stained hippocampal CA1 and CA3 pyramidal neurons dendrites. This study is the first research, to our knowledge, examining the deleterious effects of hallucinogenic methamphetamine on the stereological characteristics of hippocampal CA1 and CA3 subfields together with a morphological analysis of pyramidal neurons in the hippocampus. The quantitative findings of the current study revealed a significant decrease in numerical density and a total number of pyramidal cells in the hippocampal CA1 and CA3 subregions in both METH-treated groups compared to the control group. However, the reductions in the CA3 pyramidal cell layer did not reach statistically significant level, perhaps because of the pharmacological and neurotoxicological properties of methamphetamine. Additionally, previous studies have shown that pyramidal cells of the CA1 hippocampal subfield are more sensitive to cytotoxic effects of METH exposure than are those of the CA3 subfield of the hippocampus [28, 29]. An earlier behavioral and structural experiment demonstrated that prenatal
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Artificial association of memory events by optogenetic stimulation of hippocampal CA3 cell ensembles

Artificial association of memory events by optogenetic stimulation of hippocampal CA3 cell ensembles

The mice were deeply anesthetized with an overdose of pentobarbital solution and perfused transcardially with 4% paraformaldehyde in phosphate-buffered saline (PBS; pH 7.4). The brains were removed and further post-fixed by immersion in 4% paraformaldehyde in PBS for 24 h at 4 °C. Each brain was equilibrated in 25% sucrose in PBS and then frozen in dry-ice powder. Coronal sections of 30 μm (for ChR2-mCherry-positive cell counting) or 50 μm thickness (after in vivo recording) were cut on a cryostat and transferred to 12-well cell culture plates (Corning, Corning, NY) containing PBS. After washing with PBS, the floating sections were treated with 4′,6-dia- midino-2-phenylindole (DAPI) (1 μg/ml, 10,236,276,001; Roche Diagnostics) at room temperature for 20 min and then washed with PBS three times (3 min per wash). The sections were mounted on slide glass with ProLong Gold antifade reagent (Invitrogen of Thermo Fisher Scientific, Waltham, MA). Images were acquired on a fluorescence microscope (BZ9000; Keyence, Osaka, Japan) with a Pla- n-Apochromat 20× objective lens (Nikon, Tokyo, Japan) for ChR2-mCherry-positive cell counting or with a Plan-Apochromat 10× objective lens (Nikon) for verifi- cation of the recording site. To quantify the number of ChR2-mCherry-positive cells, images of CA3 were ac- quired by collecting z-stacks (2.4 μm apart, 5–6 im- ages). Maximum intensity projections of the images were created with the image analysis software (BZ-II; Keyence). Two sections (AP, approximately − 1.9 and − 2.0 mm from bregma) corresponding to each region of interest (ROI) (CA3 pyramidal cell layers from both hemispheres within 540 × 720 μm 2 ) were chosen from each mouse, and the ChR2-mCherry-positive cells in the ROI were counted manually. The average number of ChR2-mCherry-positive cells per section from one hemisphere are presented throughout the text.
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Action potential counting at giant mossy fiber terminals gates information transfer in the hippocampus

Action potential counting at giant mossy fiber terminals gates information transfer in the hippocampus

pyramidal cell detonation. Indeed, the CA3 pyramidal cell needs to reach firing threshold, which requires sufficient membrane depolarization. Such postsynaptic factors may include a slow membrane time constant, efficient summation of EPSPs, and synaptic inputs from other sources which could play significant roles that will need to be explored in future studies. In this context, dissecting the role of postsynaptic factors would benefit from dynamic clamp experiments. However, as short-term fa- cilitation is purely presynaptic at MF-CA3 synapses (10), we note that MF terminals can accomplish the counting function. In- deed, the experimentally constrained presynaptic release model presented here closely replicates the observed counting logic. This argues that the dynamic changes of ½Ca 2+ and of Ca 2+ buffering at release sites during AP bursts are the major con- tributors that determine short-term plasticity and AP counting in MFBs.
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Effect of tetanus toxin on extracellular levels of neuroactive amino acids and monoamines in rat hippocampus

Effect of tetanus toxin on extracellular levels of neuroactive amino acids and monoamines in rat hippocampus

underlying mechanism responsible for this observed effect remains to be elucidated. It is possible that the reduction in 5-HT re-uptake site density is a direct result of toxin-induced degeneration of serotoninergic nerve terminals in these regions. However, as mentioned previously, the ability of the injected toxin to diffuse from the dentate gyrus region to the C A l and CA3 pyramidal cell regions and induce a disinhibitory effect sufficient to produce an excitotoxic phenomenon is questionable. It has been demonstrated that most of the [ % - pai'oxetine binding in rat brain is abolished after destruction of 5-HT terminals (Habert et al, 1985; Marcusson et al, 1988). Also, an autoradiographic study on rat brain with pH]-paroxetine demonstrated that production of lesions with the potent serotoninergic neurotoxin 3,4-methylenedioxyamphetamine resulted in a dramatic decrease (> 70%) in the density of the binding sites (De Souza and Kuyatt, 1987). An approximate 50% reduction in pH]-paroxetine binding density was observed in the affected aieas in the present study. W hilst this might indicate that tetanus toxin-induced degeneration of 5-HT containing nerve terminals was responsible for the reduction in pH]-paroxetine binding density, microdialysis measurements made in toxin treated animals at this time demonstrated that the extent of reduction (approximately 22%) of extracellular 5-HlAA level did not parallel the conesponding extracellular 5-HT decrease ( approximately 65%). It therefore seems unlikely that destruction of serotoninergic nerve terminals was responsible for the reduction in 5-HT re-uptake site density.
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Experimentally verified parameter sets for modelling heterogeneous neocortical pyramidal cell populations

Experimentally verified parameter sets for modelling heterogeneous neocortical pyramidal cell populations

The neocortex is a laminar structure comprising a diversity of neuronal types, of which the principal neurons are pyramidal cells (for a review see reference [1]). Understanding how the properties of the distinct neuronal classes interact to support and govern neocortical computa- tional processes is a key challenge in neuroscience. Combined with acquisition of massive data sets, computational modelling and simulation are now central tools in the study of how the components of neural tissue interact across the genetic, cellular and functional levels [2 – 5]. In parallel with computer simulations, the mathematical framework required for a more general understanding of how cellular properties such as synaptic filtering [6, 7], synaptic dynamics [8, 9], voltage-gated or calcium-gated currents [10–12] and spike-frequency adapta- tion [13, 14] can affect network dynamics has also been extensively developed. Though these methods account for a diversity of biophysical detail, the focus has often been on networks fea- turing one or a few homogeneous populations comprised of neurons with the same level of expression of a particular biophysical characteristic.
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A Simulation-Based Study of Dorsal Cochlear Nucleus Pyramidal Cell Firing Patterns

A Simulation-Based Study of Dorsal Cochlear Nucleus Pyramidal Cell Firing Patterns

In this study, a minimal model of two variables has been presented for simulation of DCN pyramidal cells #"!<$ & inactivation properties of the transient potassium cur- re[r]

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The Pyramidal Lobe of the Thyroid

The Pyramidal Lobe of the Thyroid

Anatomy of the thyroid has been extensively studied but the presence of pyramidal lobe varies in percentages from 15% to 75% of cases according to different authors. We therefore investigated systematically this peculiar anatomical aspect. From January 2001 to December 2011, 1002 pa- tients underwent total thyroidectomy in our Division of General Surgery. We analyzed the data collected on the latest 200 thyroidectomies: for all patients pyramidal lobe was measured at re- moval of the specimen then dimension of the pyramidal lobe after fixation was checked. We found the pyramidal lobe in all cases. In most cases, it was approximately 2 cm (range 1 - 8 cm on fresh specimen). At histology it was described in 72% of cases, after fixation size decreased by a third approximatively. This is the first systematic intraoperative study to verify the prevalence of the thyroid pyramidal lobe. In our experience, the pyramidal lobe is always present and the thyrog- lossal duct is identifiable.
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Studies on the amyloid precursor protein: Implications for Alzheimer's disease

Studies on the amyloid precursor protein: Implications for Alzheimer's disease

In previous chapters, it has been proposed that in AD there may be a shift in APP processing favouring increased liberation of 6/A4. Such a change in APP metabolism would almost certainly promote ft/A4 deposition and compromise the normal biological function of APP$. The mechanism of such a shift remains unknown, however there does appear to be a relationship between cortical pyramidal neurone hypoactivity, cholinergic dysfunction and reduced non-amyloidogenic a-secretory processing of APP (see Chapter 3). As reviewed in 1.3.5.2, perturbed energy metabolism has been implicated in the pathogenesis of AD and may represent a biochemical mechanism underlying mismetabolism of APP. Using the protocol described in 2.2.7.2, cellular ATP levels were reduced by approximately 70 % in perturbed P C I2 cells compared with control. This effect was similar to previously published results (Reynolds et a l , 1982) and although ATP concentrations were reduced, the adenylate energy charge of the cells remained unchanged. This mimics the situation described in AD biopsy brain (see 1.6.8). Under these conditions, in PC12 cells, both the intracellular pool and secretion of APPLIR was found to be significantly reduced. This may index a shift away from non-amyloidogenic processing towards potentially amyloidogenic pathway(s). In one other study (Gabuzda et a l , 1994) inhibition of energy metabolism has been shown to alter the processing of APP i.e. induce a potentially amyloidogenic 11.5 kDa derivative. In addition it has been reported that PC 12 cells, when maintained under selected stressful or injurious conditions release increased quantities of a potentially amyloidogenic APP product (Baskin et a l , 1991). Therefore such an interpretation may not be without precedent. (Clearly, future studies will need to rule out more generalised reduction of protein synthesis which could also account for the reduced intracellular and secreted APPLIR and address the fate of C-terminal APPLIR derivatives under the conditions studied).
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Examination of H&E-stained sections of the hippocampus of this group revealed less prominent histological changes when compared to an AD group. CA1 and CA3, displayed the relatively apparent normal thickness of the pyramidal layer (Fig. 9A&9B). Most of the small pyramidal cells of CA1 and large pyramidal cells of CA3 appeared preserved with vesicular nuclei and pale basophilic cytoplasm. However, there are some cells with dark condensed nuclei (Fig. 9B). The molecular and polymorphic layers contained scanty normal glial cells (astrocytes) and blood capillaries (Fig. 9B). The histological architecture of DG was mostly preserved, where its granular cells were compactly arranged with rounded pale vesicular nuclei (Fig. 9C).
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The mechanisms for pattern completion and pattern separation in the hippocampus

The mechanisms for pattern completion and pattern separation in the hippocampus

The mechanisms for pattern completion and pattern separation are described in the context of a theory of hippocampal function in which the hippocampal CA3 system operates as a single attractor or autoassociation network to enable rapid, one-trial, associations between any spatial location (place in rodents, or spatial view in primates) and an object or reward, and to provide for completion of the whole memory during recall from any part. The factors important in the pattern completion in CA3 together with a large number of independent memories stored in CA3 include a sparse distributed representation which is enhanced by the graded firing rates of CA3 neurons, representations that are independent due to the randomizing effect of the mossy fibers, heterosynaptic long-term depression as well as long-term potentiation in the recurrent collateral synapses, and diluted connectivity to minimize the number of multiple synapses between any pair of CA3 neurons which otherwise distort the basins of attraction. Recall of information from CA3 is implemented by the entorhinal cortex perforant path synapses to CA3 cells, which in acting as a pattern associator allow some pattern generalization. Pattern separation is performed in the dentate granule cells using competitive learning to convert grid-like entorhinal cortex firing to place-like fields. Pattern separation in CA3, which is important for completion of any one of the stored patterns from a fragment, is provided for by the randomizing effect of the mossy fiber synapses to which neurogenesis may contribute, by the large number of dentate granule cells each with a sparse representation, and by the sparse independent representations in CA3. Recall to the neocortex is achieved by a reverse hierarchical series of pattern association networks implemented by the hippocampo-cortical backprojections, each one of which performs some pattern generalization, to retrieve a complete pattern of cortical firing in higher-order cortical areas.
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Transient extracellular application of gold nanostars increases hippocampal neuronal activity

Transient extracellular application of gold nanostars increases hippocampal neuronal activity

There is increasing evidence that nanoparticles made of different materials and shapes can be fatally toxic to the brain [8-10]. However, little is known about the non- fatal effects on the electrical activity of neurons. We found that a transient extracellular application of gold star-shaped nanoparticles increases the mean firing rate of CA3 hippocampal neurons. A very recent article [11] shows that intracellular injection of gold nanoparticles in the CA1 pyramidal neurons in the hippocampus results in an increase in the excitability of these cells. Our results are consistent with this report and further contribute to suggest that the site of action of the gold nanoparticles is on potassium channels. In our case, given that the re- ported uptake of gold nanoparticles takes much longer [12] than the effects that we measured, we hypothesize that the nanoparticles are mostly on the surface of the cells. Nanoparticles binding to potassium channels could affect their function by modifying their conformational state through adsorption [13], direct blocking [14] or clus- tering channels by cross-linking [15].
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Mechanisms of Astrocytic Calcium Wave Propagation and In Vitro Hippocampal Cell Death Are Determined By The Magnitude Of Mechanical Injury

Mechanisms of Astrocytic Calcium Wave Propagation and In Vitro Hippocampal Cell Death Are Determined By The Magnitude Of Mechanical Injury

pharmacological treatment has been successfully developed to help patients recover from TBI. A more complete understanding of both the immediate cellular reactions to injury and the longer-term responses may present new strategies for reducing damage and promoting repair. In this dissertation we first examine the ability for astrocytes to modulate the mechanisms of calcium wave propagation in response to increasing degrees of injury. As injury magnitude increases, the complexity of the calcium wave that is transmitted to surrounding uninjured regions also increases. At very mild levels of stretch calcium waves are primarily transmitted through extracellular ATP. As the level of stretch increases, gap junction communication and metabotropic glutamate receptor activation can be detected. The interaction between these three signaling pathways may transmit information about the severity of injury to surrounding astrocytes and may mediate immediate cellular responses. We also observe that the mechanical properties of cultured astrocytes are altered 24 hours after injury. Rapid stretch induces a decrease in the apparent Young’s modulus on non- nuclear regions of astrocytes, indicating that the cells are softer and more compliant. This change is associated with an upregulation of GFAP, which is a common marker for reactive gliosis. Finally, we investigate the interaction between glutamatergic and purinergic signaling in mediating cell death in hippocampal slices 24 hours following mechanical injury. Within the CA3 region of the hippocampus there is a significant increase in cell death after stretch-injury that can be attenuated by inhibiting the activity of the glutamatergic N-methyl D-aspartate (NMDA) receptors. Alternatively, blocking the activity of P2Y1 receptors is effective in limiting cell death. Our studies suggest that there is a high probability that P2Y1 receptor activity on astrocytes is responsible for inducing the over-excitation of extrasynaptic NMDA receptors, which is responsible for a major component of the observed cell death. Further studies into this pathway may lead to new approaches for pharmacological therapies after TBI.
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Expression of one important chaperone protein, heat shock protein 27, in neurodegenerative diseases

Expression of one important chaperone protein, heat shock protein 27, in neurodegenerative diseases

Within our control group, there was variability in the expression of HSP27. In some control subjects similar (to AD and FTLD), although less intense, HSP27 changes were present in the cytoplasm of pyramidal neurons of the cerebral cortex, and again as diffuse clusters of similar granules within glial cells. Such changes probably reflect the mild AD-type pathological changes present in such control subjects. In a recent study of patients with amnes- tic mild cognitive impairment (aMCI), a transitional stage between normal ageing and AD, there was a significant increase (200%) in the expression of HSP27 in the hippo- campus in the aMCI group compared to controls [28], which would be consistent with these ‘intermediate’ histo- logical findings.
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Synaptic transmission between CA3 and CA1 neurones in the guinea pig hippocampal slice

Synaptic transmission between CA3 and CA1 neurones in the guinea pig hippocampal slice

While the projection from CA3 to the ipsilateral CA1 region (the Schaffer collateral pathway) is the focus of attention for this study, it should be noted that efferents are also supplied to other regions. Swanson and Cowan (1977) have shown that the CA3 field projects to the subiculum and entorhinal cortex ipsilaterally, to the contralateral CA3 and CA1 regions (via the ventral hippocampal commissure) and to the septal nuclei of both sides. Simultaneous retrograde labelling with different fluorescent dyes has indicated that individual CA3 cells may send collaterals to three or more of these target regions (Swanson et al, 1980). Injection of horseradish peroxidase (HRP) into single CA3 pyramidal cells has revealed extensive axonal arborizations into areas CA3 and CA1 of both sides, and into the septum (Tamamaki et al, 1984).
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The neuronal morphology of the chick (Gallus domesticus) hippocampus: A Golgi study

The neuronal morphology of the chick (Gallus domesticus) hippocampus: A Golgi study

The hippocampal complex (dorsomedial forebrain) is situated on the dorsomedial surface of the avian telencephalic hemisphere. The hippocampus is subdivided into two main structures, dorsal parahippocampal area and a ventral hippocampus. Neuronal morphology of the hippocampal complex were described and located following Golgi impregnation technique. In the present study neurons of the hippocampal complex are classified into three main types: bitufted, multipolar, and pyramidal neurons. The pyramidal neurons are found to be dominant neuronal types mixed with bitufted and multipolar neurons. The pyramidal neurons have pyramidal like medium sized somata with apical and basal dendritic extension. The multipolar neurons have medium sized soma which extends dendrites in all directions. The bitufted neurons show tuft on both the pole of the cell body. The bitufted neurons of the present study show resemblance in having tufts at both the ends, with the reptilian cerebral cortex neurons. The pyramidal neurons found in the present research are not well developed as found in the mammalian cerebral cortex where they are dominant type showing clear apical and basal dendritic extentions. The multipolar neurons have been observed to be main neuronal types in the present study and also in other birds, showing well developed characteristics.
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Experimental Technique with a Pyramidal Indenter Demonstrating The Development of Pyramidal-Shaped Crevice Corrosion In Inconel 600

Experimental Technique with a Pyramidal Indenter Demonstrating The Development of Pyramidal-Shaped Crevice Corrosion In Inconel 600

From these observations, it was again demonstrated that the work piece or component made of Inconel alloy experienced accelerated crevice corrosion where it was indented, scratched, or contained pores. It was also observed that the localized surface crevice corrosion mirrored the pyramidal geometry of the initial indentation. These microscope observations again showed that in order to have perform with high corrosion resistance, the surface of the Inconel alloy must be free of pores, microvoids, and hardness indentations.

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HGF regulates the development of cortical pyramidal dendrites

HGF regulates the development of cortical pyramidal dendrites

Forty-eight hours after transfection, layer 2 pyramidal neurons of the somatosensory cortex were studied with an Axioplan Zeiss laser scanning confocal microscope. Thirty minutes fixation with 4% paraformaldehyde in PBS and DAPI counterstaining was used to confirm the laminar localization. For every experimental condition studied, the dendritic organization of between 50 and 60 neurons was reconstructed and analysed. GFP-expressing cells were selected for analysis only if they where in layer 2 of the somatosensory cortex and they had a pyramidal morphology with a single apical dendrite oriented toward the dorsal cortical surface and at least two basal dendrites. For each neuron, 15 and 20 optical sections were obtained using 20× and 40× water immersion objectives. Three-dimensional projections were generated by merging the resulting Z stacks, and the dendritic arbors were traced using LSM510 software. These traces were analyzed using a customized matlab script for the automatic counting of branching points, number of primary dendrites, dendritic length and other topological parameters. Sholl analysis was also carried out on the Z-stack images. For this analysis, concentric, digitally generated rings, 15 µm apart, were centered on the cell soma, and the number of dendrites intersecting each ring was counted (Sholl, 1953). Pair-wise comparisons were made using Student’s t-test. For multiple comparisons, ANOVA was performed followed by Fisher’s post-hoc test.
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Flexible theta sequence compression mediated via phase precessing interneurons

Flexible theta sequence compression mediated via phase precessing interneurons

determines the rate of phase precession (Figure 2C), is not generated by previous models. The dynamics inside the place field in our model take place almost entirely within this novel frequency pulling regime, with the phase locking regime instead governing the dynamics outside of the place field and therefore the alignment of spike phase at place field entry. Because our model relies on the frequency pulling rather than the phase locking regime to produce phase precession, continuous phase precession can be generated for arbitrary input profiles of sufficient strength, and does not require a monotonically increasing ramp input as in previous models (Figure 2—figure supplement 1). Second, for symmetrical place fields previous schemes predict a phase advance towards the cen- ter of a place field, but a phase reversal as the input current is reduced on leaving the place field (Melamed et al., 2004). In contrast, when input currents are sufficient to drive the neuron into the frequency pulling domain in our model, then phase advances continuously throughout the input field (Figure 2D,E). Provided that inputs are sufficiently strong and sustained, the phase of interneuron firing advances through a full 360 degrees, with the rate of phase precession determined by the strength of the injected current (Figure 2D,E). Hence, this reduced model explains the dynamics observed in the network simulation of Figure 1. Specifically, the interneuron remains in a stable phase locking regime while the pyramidal cell is inactive, but enters the frequency pulling regime whenever the pyramidal cell provides sufficient synaptic input, producing phase precession. Phase precessing synaptic inputs from the interneuron coordinate the spike timing of the pyramidal cell and confer phase precession, but phase precession in the interneuron is relatively insensitive to the timing of pyramidal cell inputs, instead requiring only a sufficient increase in excitatory drive. Figure 2. Phase precession
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<p>Phosphorylation of Tau and &alpha;-Synuclein Induced Neurodegeneration in MPTP Mouse Model of Parkinson&rsquo;s Disease</p>

<p>Phosphorylation of Tau and &alpha;-Synuclein Induced Neurodegeneration in MPTP Mouse Model of Parkinson&rsquo;s Disease</p>

It is well known that GSK3 β is one of the kinases that phosphorylate Tau. Phosphor GSK3 β Y216, the activated form of GSK3 β , was increased in multiple brain areas including MB, SN, hippocampal DG and CA3 (Figure 4A – E). Thus, Tau phosphorylation in PD mouse model might be GSK3 β -dependent. Tau phosphorylation and A β aggregation are pathological characteristics of AD. 41 Phosphorylation of Tau including Thr231, Ser202/Thr205 and Ser396 sites occur in the AD progression. 7 However, Tau phosphorylation at Ser202/Thr205 site was observed in our PD mouse model (Figure 2D), suggesting that Tau phosphorylation is also a pathological feature of PD. Using AZD 1080, a speci fi c GSK3 β inhibitor, alleviated the Tau phosphorylation level in this PD model, suggested that Tau phosphorylation in this PD model might through GSK3 β pathway. Furthermore, p- α -Synuclein partially colocalized with p-Tau in Hippo and SN, and p- α -
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