Normal Adult Rat Brain Research Articles

Comparative Analysis of the Expression of Chondroitin Sulfate Subtypes and Their Inhibitory Effect on Axonal Growth in the Embryonic, Adult, and Injured Rat Brains.

Chondroitin sulfate glycosaminoglycans (CS-GAGs) are the primary inhibitory GAGs for neuronal growth after central nervous system (CNS) injury. However, the inhibitory or permissive activity of CS-GAG subtypes is controversial and depends on the physiological needs of CNS tissues. In this study, we investigated the characteristics and effects of CS-GAGs on axonal growth, which was isolated from the brain cortices of normal rat embryo at E18, normal adult rat brain and injured adult rat brain. Isolated CS-GAGs from embryo, normal adult, and injured adult rat brains were used for analyzing their effect on attachment and axonal growth using modified spot assay with dorsal root ganglion (DRG) explants and cerebellar granule neurons (CGNs). CS-GAGs were separated using high performance liquid chromatography (HPLC), and the subtypes of CS-GAGs were analyzed. CS-GAGs of all three groups inhibited CGN attachment and axonal growth of DRGs. However, CS-GAGs of normal adult rat brain exhibited higher inhibitory activity than those of the other groups in both assays. When subtypes of CS-GAGs were analyzed using HPLC, CS-A (4S) was the most abundant in all three groups and found in largest amount in normal adult rat brain. In contrast, unsulfated CS (CS0) and CS-C (6S) were more abundant by 3-4-folds in E18 group than in the two adult groups. When compared with the normal adult rat brain, injured rat brain showed relatively similar patterns to that of embryonic rat brain at E18 in the expression of CS subtypes and their inhibitory effect on axonal growth. This phenomenon could be due to differential expression of CS-GAGs subtypes causing decrease in the amount of CS-A and mature-type CS proteoglycan core proteins.

MTORC1 and mTORC2 expression in inner retinal neurons and glial cells

The retina is one of the most metabolically active tissues, yet the processes that control retinal metabolism remains poorly understood. The mTOR complex (mTORC) that drives protein and lipid biogenesis and autophagy has been studied extensively in regards to retinal development and responses to optic nerve injury but the processes that regulate homeostasis in the adult retina have not been determined. We previously demonstrated that normal adult retina has high rates of protein synthesis compared to skeletal muscle, associated with high levels of mechanistic target of rapamycin (mTOR), a kinase that forms multi-subunit complexes that sense and integrate diverse environmental cues to control cell and tissue physiology. This study was undertaken to: 1) quantify expression of mTOR complex 1 (mTORC1)- and mTORC2-specific partner proteins in normal adult rat retina, brain and liver; and 2) to localize these components in normal human, rat, and mouse retinas. Immunoblotting and immunoprecipitation studies revealed greater expression of raptor (exclusive to mTORC1) and rictor (exclusive for mTORC2) in normal rat retina relative to liver or brain, as well as the activating mTORC components, pSIN1 and pPRAS40. By contrast, liver exhibits greater amounts of the mTORC inhibitor, DEPTOR. Immunolocalization studies for all three species showed that mTOR, raptor, and rictor, as well as most other known components of mTORC1 and mTORC2, were primarily localized in the inner retina with mTORC1 primarily in retinal ganglion cells (RGCs) and mTORC2 primarily in glial cells. In addition, phosphorylated ribosomal protein S6, a direct target of the mTORC1 substrate ribosomal protein S6 kinase beta-1 (S6K1), was readily detectable in RGCs, indicating active mTORC1 signaling, and was preserved in human donor eyes. Collectively, this study demonstrates that the inner retina expresses high levels of mTORC1 and mTORC2 and possesses active mTORC1 signaling that may provide cell- and tissue-specific regulation of homeostatic activity. These findings help to define the physiology of the inner retina, which is key for understanding the pathophysiology of optic neuropathies, glaucoma and diabetic retinopathy.

The Impact of the Ketogenic Diet on Glial Cells Morphology. A Quantitative Morphological Analysis

Ketogenic diet is reported to protect against cognitive decline, drug-resistant epilepsy, Alzheimer's Disease, damaging effect of ischemic stroke and many neurological diseases. Despite mounting evidence that this dietary treatment works, the exact mechanism of its protective activity is largely unknown. Ketogenic diet acts systemically, not only changing GABA signaling in neurons, but also influencing the reliance on mitochondrial respiration, known to be disrupted in many neurological diseases. Normally, human body is driven by glucose while ketogenic diet mimics starvation and energy required for proper functioning comes from fatty acids oxidation. In the brain astrocytes are believed to be the sole neural cells capable of fatty oxidation. Here we try to explain that not exclusively neurons, but also morphological changes of astroglia and/or microglia due to different metabolic state are important for the mechanism underlying the protective role of ketogenic diet. By quantifying different parameters describing cellular morphology like ramification index or fractal dimension and using Principal Component Analysis to discover the regularities between them, we demonstrate that in normal adult rat brain, ketogenic diet itself is able to change glial morphology, indicating an important role of these underappreciated cells in the brain metabolism.

Nestin expression and invivo proliferative potential of tanycytes and ependymal cells lining the walls of the third ventricle in the adult rat brain.

There is a disagreement in the literature concerning the degree of proliferation of cells in the walls of the third ventricle (3rdV) under normal conditions in the adult mammalian brain. To address this issue, we mapped the cells expressing the neural stem/progenitor cell marker nestin along the entire rostrocaudal extent of the 3rdV in adult male rats and observed a complex distribution. Abundant nestin was present in tanycyte cell bodies and processes and also was observed in patches of ependymal cells as well as in isolated ependymal cells throughout the walls of the 3rdV. However, we observed very limited ependymal cell or tanycyte proliferation in normal adult rats as determined by bromodeoxyuridine (BrdU) incorporation or the expression of Ki-67. Moreover, fewer than 13% of the cells that were BrdU-positive (BrdU+) or Ki-67-positive (Ki-67+) expressed nestin. These observations stand in contrast to those made in the subventricular zone of the lateral ventricle (SVZ) and subgranular zone of the hippocampal formation (SGZ), where cell proliferation measured by BrdU incorporation or Ki-67 expression is observed frequently in cells that also express nestin. Thus, while ependymal cell or tanycyte cell proliferation can be promoted by the addition of mitogens, dietary modifications or other invivo manipulations, the proliferation of ependymal cells and tanycytes in the walls of the 3rdV is very limited in the normal adult male rat brain.

Transplantation of Embryonic Ventral Mesencephalic Tissue in 6-OHDA Induced Parkinsonism Rat Brain for Cell Based Therapy: A Perspective of Methods

Parkinson’s disease (PD) is characterized as a disease of the basal ganglia, with a progressive degeneration of dopaminergic neurons located in the substantia nigra (SN) and projecting to the striatum with subsequently loss of the nigrostriatal circuit. The potential for therapeutic use of cell transplantation for cell replacement has received a great deal of interest. Transplantation with embryonic ventral mesencephalon (VM) is a therapeutic approach for sporadic form of PD. We established unilaterally 6-OHDA lesioned rat model of Parkinson’s disease. Motor behavioral impairment was found compared with normal rat. Embryonic VM tissue was isolated from E 14 (embryonic 14 days) rat brain. We characterized the VM tissue and dissociated cultured dopaminergic cells with tyrosine hydroxylase (TH) immune staining before transplantation in lesioned brain. We observed that the axons of dopaminergic neurons from transplanted VM graft circles round at the site of transplantation in normal adult rat brain. In this paper, we discuss the detailed methodologies which are very useful in preclinical research of cell based therapies for Parkinson’s disease.

Transplantation of Embryonic Ventral Mesencephalic Tissue in 6-OHDA Induced Parkinsonism Rat Brain for Cell Based Therapy: A Perspective of Methods

Parkinson’s disease (PD) is characterized as a disease of the basal ganglia, with a progressive degeneration of dopaminergic neurons located in the substantia nigra (SN) and projecting to the striatum with subsequently loss of the nigrostriatal circuit. The potential for therapeutic use of cell transplantation for cell replacement has received a great deal of interest. Transplantation with embryonic ventral mesencephalon (VM) is a therapeutic approach for sporadic form of PD. We established unilaterally 6-OHDA lesioned rat model of Parkinson’s disease. Motor behavioral impairment was found compared with normal rat. Embryonic VM tissue was isolated from E 14 (embryonic 14 days) rat brain. We characterized the VM tissue and dissociated cultured dopaminergic cells with tyrosine hydroxylase (TH) immune staining before transplantation in lesioned brain. We observed that the axons of dopaminergic neurons from transplanted VM graft circles round at the site of transplantation in normal adult rat brain. In this paper, we discuss the detailed methodologies which are very useful in preclinical research of cell based therapies for Parkinson’s disease.

Characteristics of brain cell proliferation and migration in animals with experimental Alzheimer’s disease undergoing cognitive training

Aims. Alzheimer’s disease is a multifactorial neurodegenerative disease characterized by the presence of amyloid beta peptide containing plaques, and neurofibrillary tangles. Beta-amyloid is a major risk factor and it plays a central role in the onset and progression of Alzheimer’s disease. However, question of the influence of beta-amyloid on neurogenesis in the hippocampus in the adult brain is still open. The purpose of this paper is to study cognitive functions and their association with proliferation, survival and migration of newly-formed cells in normal adult rat brain and in the experimental Alzheimer’s disease. Materials and methods. Rats (Wistar, males, 7 months) were used. Experimental group (Alzheimer’s disease model with the intrahippocampal administration of beta-amyloid 1-42 (5 µl) bilaterally in the CA1 area) and a control group (sham-operated animals with the intrahippocampal administration of Phosphate buffered salin (5 µl) bilaterally in the CA1) have been tested. The study was conducted from February to July. Neurobehavioral test (Morris water maze) was used to assess working memory and memory consolidation. The study of cell migration was performed by introducing bromodeoxyuridine (50 mg/kg). Expression of neurogenesis markers in the subgranular zone of the dentate gyrus of the hippocampus was studied has been studied with indirect immunohistochemistry for free-floating sections followed by the confocal microscopy. Results. Modelling of Alzheimer’s disease leads to impaired cognitive function and memory in animals. We found that these events were associated with the suppression of proliferative (р = 0,043) and migratory activity of brain cells (р = 0,031), but not survival of cells (p = 0,985) compared to the control group.Training in Morris water maze of animals with experimental Alzheimer’s disease promotes migration of progenitor cells along the rostral migration way (р = 0,011) compared with the group without training. However, the number of neuroblasts (р = 0,809) and proliferation of neuronal progenitor cells (p = 0,083) were not significantly affected compared with the group without training. Conclusions. Decreased level of brain cells proliferation, alterations in their migration and development of cognitive dysfunction have been found in the rat model of Alzheimer’s disease, thus suggesting impairment of neurogenesis induced by amyloid. Possible involvement of local insulin resistance into the development of neurogenesis alterations is discussed.

Comparison of unbiased estimation of neuronal number in the rat hippocampus with different staining methods

BackgroundNeuN and Nissl staining (toluidine blue, cresyl violet staining) are routinely used methods in unbiased stereological estimation of the total number of hippocampal neurons. New methodIn the present study, we stained serial frozen coronal sections from 5 normal adult male Sprague-Dawley rat brains with different methods, measured the deformation of hippocampal area in brain sections and estimated the total number of hippocampal neurons using the optical fractionator. ResultsThe deformation in x, y-axis was not obviously different with different staining protocols, but shrinkage in z-axis was significant after staining (p<0.001). NeuN staining produced significant higher estimate number than cresyl violet staining by 24% (p=0.002), however, NeuN and Cresyl Violet staining showed a high degree of correlation in quantification of total neuronal numbers and both methods are suitable for unbiased stereological estimation. Comparison with existing method (s)NeuN is more reliable but if time is limited or the number of animals used in experiments is high, cresyl violet staining may be a feasible method. ConclusionsCompared with previous estimates of the neurons number in rat hippocampus, our present data is reliable and the stereological analysis based on our system is a cost-effective unbiased method for estimation of neuron number.

Loss of Nogo-A-expressing neurons in a rat model of Parkinson’s disease

The myelin-associated protein Nogo-A is among the most potent neurite growth inhibitors in the adult CNS. Recently, Nogo-A expression was demonstrated in a number of neuronal subpopulations of the adult and developing CNS but at present, little is known about the expression of Nogo-A in the nigrostriatal system, a brain structure severely affected in Parkinson’s disease (PD). The present study sought to characterize the expression pattern of Nogo-A immunoreactive (ir) cells in the adult ventral mesencephalon of control rats and in the 6-hydroxydopamine (6-OHDA) rat model of PD. Immunohistochemical analyses of normal adult rat brain showed a distinct expression of Nogo-A in the ventral mesencephalon, with the highest level in the substantia nigra pars compacta (SNc) where it co-localized with dopaminergic neurons. Analyses conducted 1week and 1 month after unilateral striatal injections of 6-OHDA disclosed a severe loss of the number of Nogo-A-ir cells in the SNc. Notably, at 1week after treatment, more dopaminergic neurons expressing Nogo-A were affected by the 6-OHDA toxicity than Nogo-A-negative dopaminergic neurons. However, at later time points more of the surviving dopaminergic neurons expressed Nogo-A. In the striatum, both small and large Nogo-A-positive cells were detected. The large cells were identified as cholinergic interneurons. Our results suggest yet unidentified functions of Nogo-A in the CNS beyond the inhibition of axonal regeneration and plasticity, and may indicate a role for Nogo-A in PD.

Redirection of doublecortin-positive cell migration by over-expression of the chemokines MCP-1, MIP-1α and GRO-α in the adult rat brain

Inflammation-induced chemoattraction plays a major role in adult subventricular zone (SVZ)-derived precursor cell migration following neural cell loss, in particular through the release of chemokines by activated microglia and macrophages. We previously demonstrated that monocyte chemotactic protein-1 (MCP-1) (chemokine (c-c motif) ligand (CCL)2), macrophage inflammatory protein-1α (MIP-1α) (CCL3) and growth regulatory protein-α (GRO-α) (chemokine (c-x-c motif) ligand (CXCL)1) are up-regulated following neural cell loss in the adult striatum and act as potent chemoattractants for SVZ-derived precursor cells in vitro. Based on these observations, the current study aimed to examine the individual effect of MCP-1, MIP-1α and GRO-α on the migration of adult SVZ-derived neural precursor cells in vivo. To address this without the confounding effects of injury-induced chemotactic cues, adeno-associated viral (AAV)2-mediated in vivo gene transfer was used to ectopically express either MCP-1, MIP-1α or GRO-α, or the control red fluorescent protein (RFP) in the normal adult rat striatum. The extent of doublecortin (Dcx)-positive cell recruitment from the SVZ into the striatal parenchyma was then determined at 4 and 8weeks following AAV2 injection. Ectopic expression either of MCP-1 or MIP-1α in the normal adult rat brain significantly increased the number of Dcx-positive cells and the extent of their migration into the striatum at both 4 and 8weeks after vector injection but did not promote either precursor cell proliferation or neural differentiation. In contrast, while over-expression of GRO-α 4weeks after vector injection induced a significant increase in Dcx-positive cell migration compared to control, this effect was reduced to control levels by 8weeks post injection. Further, direct comparison between MCP-1, MIP-1α and GRO-α at both 4 and 8weeks post vector injection indicated that GRO-α may have a reduced effect in inducing Dcx-positive cell migration when compared to MCP-1. Combined, these results confirm that over-expression of the chemokines MCP-1, MIP-1α and GRO-α can override cues directing precursor cell migration along the rostral migratory stream (RMS) and provides a mechanism by which neural precursor cell migration can be redirected into a non-neurogenic region. Differences in the migratory effect observed between individual chemokine may be due to ligand-binding affinity and/or receptor expression on SVZ-derived precursor cells.

IGF-I redirects doublecortin-positive cell migration in the normal adult rat brain

The migration of subventricular zone (SVZ)-derived neural precursor cells through the rostral migratory stream (RMS) to the olfactory bulb is tightly regulated by local micro-environmental cues. Insulin-like Growth Factor-I (IGF-I) can stimulate the migration of several neuronal cell types and acts as a ‘departure’ factor in the avian SVZ. To establish whether IGF-I can also act as a migratory factor for adult neuronal precursor cells in vivo, in addition to its well established role in precursor cell proliferation and differentiation, we used AAV2-mediated gene transfer to produce ectopic expression of IGF-I in the normal adult rat striatum. We then assessed whether the expression of IGF-I would recruit SVZ-derived neuronal precursor cells from the RMS into the striatum. Ectopic expression of IGF-I in the normal adult rat brain significantly increased the number of doublecortin (Dcx)-positive cells and the extent of their migration into the striatum 4 and 8weeks after AAV2–IGF-I injection but did not promote neuronal differentiation. In vitro migration assays confirmed that IGF-I is an inducer of migration and directs SVZ-derived adult neuronal precursor cell migration by both chemotaxis and chemokinesis. These results demonstrate that overexpression of IGF-I in the normal adult rat brain can override the normal cues directing precursor cell migration along the RMS and can redirect precursor cell migration into a non-neurogenic region. Enhanced expression of IGF-I following brain injury may therefore act as a diffusible factor mediating precursor cell migration to areas of neuronal cell damage.

Population-averaged diffusion tensor imaging atlas of the Sprague Dawley rat brain

Rats are widely used in experimental neurobiological research, and rat brain atlases are important resources for identifying brain regions in the context of experimental microsurgery, tissue sampling, and neuroimaging, as well as comparison of findings across experiments. Currently, most available rat brain atlases are constructed from histological material derived from single specimens, and provide two-dimensional or three-dimensional (3D) outlines of diverse brain regions and fiber tracts. Important limitations of such atlases are that they represent individual specimens, and that finer details of tissue architecture are lacking. Access to more detailed 3D brain atlases representative of a population of animals is needed. Diffusion tensor imaging (DTI) is a unique neuroimaging modality that provides sensitive information about orientation structure in tissues, and is widely applied in basic and clinical neuroscience investigations. To facilitate analysis and assignment of location in rat brain neuroimaging investigations, we have developed a population-averaged three-dimensional DTI atlas of the normal adult Sprague Dawley rat brain. The atlas is constructed from high resolution ex vivo DTI images, which were nonlinearly warped into a population-averaged in vivo brain template. The atlas currently comprises a selection of manually delineated brain regions, the caudate-putamen complex, globus pallidus, entopeduncular nucleus, substantia nigra, external capsule, corpus callosum, internal capsule, cerebral peduncle, fimbria of the hippocampus, fornix, anterior commisure, optic tract, and stria terminalis. The atlas is freely distributed and potentially useful for several purposes, including automated and manual delineation of rat brain structural and functional imaging data.

Peripheral growth hormone induces cell proliferation in the intact adult rat brain

Growth hormone (GH) and insulin-like growth factor I (IGF-I) increase cell genesis in several regions of the brains of GH-IGF-I-deficient hypophysectomized rats. However, it is not known to what degree GH treatment stimulates adult cell genesis in pituitary-intact rodents. We investigated the effect of peripheral administration of bovine growth hormone (bGH) on cellular proliferation in various regions of the brains of normal adult female rats. To monitor cell division, bromodeoxyuridine (BrdU) was administered daily for 5 days. We studied the two areas of ongoing neurogenesis, the subventricular zone (SVZ) and the dentate gyrus (DG) of the hippocampus, as well as the corpus callosum, striatum, and the parietal and piriform cortices. After bGH treatment, the numbers of BrdU-positive cells increased 2.0- to 2.5-fold in all the brain regions, with the exception of the SVZ, in which there was no increase in the numbers of BrdU-positive cells. The present study shows for the first time that peripheral bGH administration increases the generation of new brain cells in normal adult female rats. Thus, bGH may stimulate cellular proliferation not only under GH-deficiency, but also under physiologic conditions. These findings have important implications for GH treatment strategies for patients who have normal or near-normal circulating levels of GH or IGF-I.

Differential Expression of PTEN in Normal Adult Rat Brain and Upregulation of PTEN and p‐Akt in the Ischemic Cerebral Cortex

The tumor suppressor phosphatase and tensin homologue (PTEN) is a protein and lipid phosphatase. PTEN mutations have been associated with a large number of human cancers. To understand the physiological role of PTEN in the brain and its relationship to Akt in ischemic injury, we first investigated the localization of PTEN immunoreactivity in the brains of normal adult rats using immunohistochemistry. We then detected the modulation of PTEN and p-Akt following transient global ischemia by Western blot and immunohistochemistry analyses. Our observation of normal brains showed that PTEN was heterogeneously distributed in the cytoplasm, nuclei, and processes in different regions. It was shown immunohistochemically that PTEN was distributed differentially in rat brain, with the highest levels in the anterior olfactory nucleus, cerebral cortex, amygdaloid nucleus, hippocampus, Purkinje's cells, and several nuclei in the basal ganglia, thalamus, midbrain, and pons. After global cerebral ischemia, PTEN and p-Akt immunoreactivities were increased in the cerebral cortex. This was accompanied by the nuclear translocation of p-Akt. Double-labeling experiments revealed that PTEN and p-Akt were most likely localized to neurons. These results suggest a role for PTEN in normal adult brain and that the PTEN/Akt pathway may be involved in neuronal survival or plasticity after ischemic injury.

Inhibition of Autophagy Causes Tau Proteolysis by Activating Calpain in Rat Brain

The autophagic lysosomal system contributes to the removal of cytosolic components, and abnormality of lysosomal proteases has been reported in the brain of patients with Alzheimer's disease (AD). However, the role of lysosome in tau degradation is still elusive. Here, we infused chloroquine, 3-methyladenine or rapamycin into rat hippocampus or the lateral ventricle to manipulate the autophagic activity and measured the levels of tau protein by Western blotting. We unexpectedly observed that the level of different tau species decreased upon inhibition of lysosomal proteases or macroautophagy by chloroquine or 3-methyladenine. Furthermore, induction of autophagic activity by rapamycin did not induce degradation of tau proteins. To explore the underlying mechanisms for the increased tau degradation induced by autophagic inhibition, we used MG-132, an inhibitor of proteasome and calpain. We found that simultaneous inhibition of proteasome and calpain by MG-132 prevented the chloroquine-induced tau degradation. Further studies demonstrated that the activity of calpain was elevated whereas the activity of proteasome was suppressed in response to inhibition of autophagy by 3-methyladenine or chloroquine. Our data suggest that the lysosomal autophagic system may not degrade tau in the normal adult rat brain and inhibition of autophagy may induce tau proteolysis through activating calpain.

Expression of neuronal proteins in cells from normal adult rat brain propagated in serial culture.

Cells have been cultured from the brains of 60-day-old rats and propagated through 12 passages. The cells contain the high and middle, but not low, molecular weight neurofilament subunits and neuron-specific enolase, demonstrated by immunoblotting and immunocytochemistry with redundant antibodies. The cells did not have the morphology of neurons when cultured in medium containing fetal calf serum and growth factors. In low serum medium containing the same growth factors with the addition of dibutyryl cyclic AMP, the cells became smaller and developed long processes. Three clonal lines derived from these cultures had the same properties. These observations are in agreement with recent observations using mouse and human brain tissue and demonstrate that proteins normally associated with neurons can be found in dividing cells cultured from the brains of young adult rats.

Towards better MR characterization of neural tissues using directional diffusion kurtosis analysis

MR diffusion kurtosis imaging (DKI) was proposed recently to study the deviation of water diffusion from Gaussian distribution. Mean kurtosis, the directionally averaged kurtosis, has been shown to be useful in assessing pathophysiological changes, thus yielding another dimension of information to characterize water diffusion in biological tissues. In this study, orthogonal transformation of the 4th order diffusion kurtosis tensor was introduced to compute the diffusion kurtoses along the three eigenvector directions of the 2nd order diffusion tensor. Such axial ( K //) and radial ( K ┴) kurtoses measured the kurtoses along the directions parallel and perpendicular, respectively, to the principal diffusion direction. DKI experiments were performed in normal adult ( N = 7) and formalin-fixed rat brains ( N = 5). DKI estimates were documented for various white matter (WM) and gray matter (GM) tissues, and compared with the conventional diffusion tensor estimates. The results showed that kurtosis estimates revealed different information for tissue characterization. For example, K // and K ┴ under formalin fixation condition exhibited large and moderate increases in WM while they showed little change in GM despite the overall dramatic decrease of axial and radial diffusivities in both WM and GM. These findings indicate that directional kurtosis analysis can provide additional microstructural information in characterizing neural tissues.

Neural Progenitor Cells Derived from the Adult Rat Subventricular Zone: Characterization and Transplantation

In order to fully characterize and determine the therapeutic potential of adult neural progenitor cells (NPCs), it is important to be able to isolate and study NPCs from animals such as rats, in which there are existing models of brain injury and disease. The focus of this study was to characterize the cultivation, differentiation, and transplantation of adult rat NPCs isolated from the subventricular zone of the lateral ventricles. We examined strategies for cell purification using a Percoll density gradient, and cell expansion using a range of maintenance medium and plating densities. Purification by Percoll gradient enriched a population of cells expressing nestin and SOX2, but resulted in a significant reduction in neurosphere generation. Culturing adult rat NPCs in Neurobasal-A media and plating at 200,000 cell/ml resulted in a higher percentage of cells surviving to generate neurospheres compared to culture in DMEM/F12 or NS-A media. On induction of differentiation, adult rat NPCs were capable of generating neurons, astrocytes, and oligodendrocytes in vitro that survived for up to 8 weeks, demonstrating multipotentiality of these cells. In addition, a population of cells continued to proliferate during the initial phase of differentiation, suggesting the presence of two populations of NPCs during differentiation. Cultured adult rat NPCs also survived and differentiated into astrocytes 6 weeks after transplantation into the striatum of the normal adult rat brain. In conclusion, we have optimized techniques that allow for the routine isolation, culture, and transplantation of multipotent NPCs derived from the adult rat SVZ.

Extensive nuclear localization of α-synuclein in normal rat brain neurons revealed by a novel monoclonal antibody

Synuclein was initially named for its localization in both presynaptic nerve terminals and portions of nuclear envelope. However, subsequent studies only confirmed the presynaptic localization of this protein in the brain; its nuclear localization in the neurons remained elusive. Here, two new monoclonal antibodies against α-synuclein (α-SYN) were produced. Epitope mapping using phage peptide display showed that the epitopes of the two antibodies were localized in two distinct specific sequences of the C-terminal domain of α-SYN. One antibody named 3D5 recognized amino acids 115–121 of α-SYN and the other antibody named 2E3 identified the amino acids 134–138 of the protein. Western blot analysis demonstrated that both 2E3 and 3D5 detected a 19 kD protein from rat and human brain homogenates, which was identical to the molecular size of recombinant α-SYN. However, immunohistochemical staining on normal adult rat brain sections showed that the two antibodies revealed distinct patterns of subcellular localization of α-SYN immunoreactivity. Both 3D5 and 2E3 detected the presynaptic α-SYN but only 3D5 detected the nuclear α-SYN. The nuclear localization of α-SYN was further confirmed (1) by Western blot analysis in isolated nuclear fraction where the same size of α-SYN was detected, and (2) by immunoelectron microscopy using colloidal gold probes where gold particles were specifically localized in portions of peri- and intra-nucleus. The nuclear positive neurons were distributed extensively in almost all the brain regions. This is the first report well characterizing the extensive localization of α-SYN in the neuronal nuclei throughout the brain in normal conditions. This finding indicates an important physiological function of this molecule in the nuclei of brain neurons, which deserves further investigations.

Fluoxetine and Cocaine Induce the Epigenetic Factors MeCP2 and MBD1 in Adult Rat Brain

Once bound to methylated CpG sites, methyl-CpG-binding protein 2 (MeCP2) is thought to silence transcription of downstream genes by recruiting a histone deacetylase (HDAC). Mutations within the MeCP2 gene have been found to cause Rett syndrome, a disorder of arrested neuronal development. Using immunohistochemistry, we found that Mecp2, as well as the methyl-CpG-binding protein MBD1, were significantly induced in normal adult rat brain after repeated injections of fluoxetine or cocaine for 10 days (one injection per day). Mecp2 was not induced by repeated injections of 1-(2-bis(4-fluorphenyl)-methoxy)-ethyl)-4-(3-phenyl-propyl)piperazine (GBR-12909) or nortriptyline. Together, the data indicate that the serotonergic system is predominantly involved. Using real-time reverse transcription-polymerase chain reaction experiments, MBD1 mRNA and both Mecp2_e1 and Mecp2_e2 transcripts were found to be induced by fluoxetine. Induction of the methylbinding proteins was accompanied with enhanced HDAC2 labeling intensity and mRNA synthesis in response to fluoxetine. In tandem, acetylated forms of histone H3 were found to be decreased. The effect was characterized in three serotonin projection areas, the caudate-putamen, the frontal cortex, and the dentate gyrus subregion of hippocampus. Our data highlight GABAergic neurons as major target cells expressing Mecp2 in response to the serotonin-elevating agents and suggest that serotonin signaling enhances gene silencing in postmitotic neurons.