Transcriptional dynamics orchestrating the development and integration of neurons born in the adult hippocampus.

The adult hippocampus generates new granule cells (aGCs) with functional capabilities that convey unique forms of plasticity to the preexisting circuits. While early differentiation of adult radial glia-like cells (RGLs) has been studied extensively, the molecular mechanisms guiding the maturation of postmitotic neurons remain unknown. Here, we used a precise birthdating strategy to study aGC differentiation using single-nuclei RNA sequencing. Transcriptional profiling revealed a continuous trajectory from RGLs to mature aGCs, with multiple immature stages bearing increasing levels of effector genes supporting growth, excitability, and synaptogenesis. Analysis of differential gene expression, pseudo-time trajectory, and transcription factors (TFs) revealed critical transitions defining four cellular states: quiescent RGLs, proliferative progenitors, immature aGCs, and mature aGCs. Becoming mature aGCs involved a transcriptional switch that shuts down pathways promoting cell growth, such SoxC TFs, to activate programs that likely control neuronal homeostasis. aGCs overexpressing Sox4 or Sox11 remained immature. Our results unveil precise molecular mechanisms driving adult RGLs through the pathway of neuronal differentiation.

Dual spatio-temporal regulation of axon growth and microtubule dynamics by RhoA signaling pathways.

RhoA plays a crucial role in neuronal polarization, where its action restraining axon outgrowth has been thoroughly studied. We now report that RhoA has not only an inhibitory but also a stimulatory effect on axon development depending on when and where exerts its action and the downstream effectors involved. In cultured hippocampal neurons, FRET imaging revealed that RhoA activity selectively localized in growth cones of undifferentiated neurites, whereas in developing axons it displayed a biphasic pattern, being low in nascent axons and high in elongating ones. RhoA-Rho kinase (ROCK) signaling prevented axon initiation but had no effect on elongation, whereas formin inhibition reduced axon extension without significantly altering initial outgrowth. In addition, RhoA-mDia signaling promoted axon elongation by stimulating growth cone microtubule stability and assembly, as opposed to RhoA-ROCK signaling, which restrained growth cone microtubule assembly and protrusion.

Cannabidiol protects mouse hippocampal neurons from neurotoxicity induced by amyloid ß-peptide25-35.

Alzheimer's disease (AD), the most prevalent form of dementia worldwide, is a significant health concern, according to the World Health Organization (WHO). The neuropathological diagnostic criteria for AD are based on the deposition of amyloid-ß peptide (Aß) and the formation of intracellular tau protein tangles. These proteins are associated with several overlapping neurodegenerative mechanisms, including oxidative stress, mitochondrial dysfunction, lipid peroxidation, reduced neuronal viability, and cell death. In this context, our study focuses on the potential therapeutic use of cannabidiol (CBD), a non-psychotropic cannabinoid with antioxidant and anti-inflammatory effects. We aim to evaluate CBD's neuroprotective role, particularly in protecting hippocampal neurons from Aß25-35-induced toxicity. Our findings indicate that CBD significantly improves cell viability and decreases levels of lipid peroxidation and oxidative stress. The results demonstrate that CBD possesses a robust potential to rescue cells from induced neurotoxicity through its antioxidant properties. Additionally, the neuroprotective effect of CBD may be associated with the modulation of the endocannabinoid system. These findings suggest that CBD could be a promising compound for adjuvant treatments in neurodegenerative processes triggered by amyloid-ß peptide.

Life-long arsenic exposure damages the microstructure of the rat hippocampus.

Epidemiological studies demonstrate that arsenic exposure is associated with cognitive dysfunction. Experimental arsenic exposure models showed learning and memory deficits and molecular changes resembling the functional and pathologic neurodegeneration features. The present work focuses on hippocampal pathological changes in Wistar rats induced by continuous arsenic exposure from in utero up to 12 months of age, evaluated by magnetic resonance imaging along with immunohistochemistry. Diffusion-weighted images revealed age-related lower fractional anisotropy and higher radial-axial and mean diffusivity at 6 and 12 months, indicating that arsenic exposure leads to hippocampal demyelination. These structural alterations were paralleled by immunohistochemical changes that showed a significant loss of myelin basic protein in CA1 and CA3 regions accompanied by increased glial fibrillary acidic protein expression at all time-points studied. Concomitantly, arsenic exposure induced an altered morphology of astrocytes at all studied ages, whereas increased synaptogenesis was only observed at two months of age. These results suggest that environmental arsenic exposure is linked to impaired hippocampal connectivity and perhaps early glial senescence, which together might resemble a premature aging phenomenon leading to cognitive deficits.

Adult Neurogenesis: A Story Ranging from Controversial New Neurogenic Areas and Human Adult Neurogenesis to Molecular Regulation.

The generation of new neurons in the adult brain is a currently accepted phenomenon. Over the past few decades, the subventricular zone and the hippocampal dentate gyrus have been described as the two main neurogenic niches. Neurogenic niches generate new neurons through an asymmetric division process involving several developmental steps. This process occurs throughout life in several species, including humans. These new neurons possess unique properties that contribute to the local circuitry. Despite several efforts, no other neurogenic zones have been observed in many years; the lack of observation is probably due to technical issues. However, in recent years, more brain niches have been described, once again breaking the current paradigms. Currently, a debate in the scientific community about new neurogenic areas of the brain, namely, human adult neurogenesis, is ongoing. Thus, several open questions regarding new neurogenic niches, as well as this phenomenon in adult humans, their functional relevance, and their mechanisms, remain to be answered. In this review, we discuss the literature and provide a compressive overview of the known neurogenic zones, traditional zones, and newly described zones. Additionally, we will review the regulatory roles of some molecular mechanisms, such as miRNAs, neurotrophic factors, and neurotrophins. We also join the debate on human adult neurogenesis, and we will identify similarities and differences in the literature and summarize the knowledge regarding these interesting topics.

Artepillin C, a major component of Brazilian green propolis, inhibits endoplasmic reticulum stress and protein aggregation.

Propolis, a compound produced by honeybees, has long been used in food and beverages to improve health and prevent diseases. We previously reported that the ethanol extracts of Brazilian green propolis and its constituents artepillin C, kaempferide, and kaempferol mitigate oxidative stress-induced cell death via oxytosis/ferroptosis. Here, we investigated the potential of Brazilian green propolis and its constituents to protect against endoplasmic reticulum stress in the mouse hippocampal cell line HT22. Ethanol extracts of Brazilian green propolis, artepillin C, and kaempferol attenuated tunicamycin-induced unfolded protein response and cell death. Interestingly, artepillin C inhibited both tunicamycin-induced protein aggregation in HT22 cells and the spontaneous protein aggregation of mutant canine superoxide dismutase 1 (E40K-SOD1-EGFP) in Neuro2a cells. These findings indicate that in addition to oxidative stress, the ethanol extracts of Brazilian green propolis help prevent endoplasmic reticulum stress-related neuronal cell death, which is proposedly involved in several neurodegenerative diseases. Moreover, artepillin C, a major constituent of Brazilian green propolis, may exhibit chemical chaperone-like properties.

Growth Hormone (GH) Enhances Endogenous Mechanisms of Neuroprotection and Neuroplasticity after Oxygen and Glucose Deprivation Injury (OGD) and Reoxygenation (OGD/R) in Chicken Hippocampal Cell Cultures.

As a classical growth promoter and metabolic regulator, growth hormone (GH) is involved in development of the central nervous system (CNS). This hormone might also act as a neurotrophin, since GH is able to induce neuroprotection, neurite growth, and synaptogenesis during the repair process that occurs in response to neural injury. After an ischemic insult, the neural tissue activates endogenous neuroprotective mechanisms regulated by local neurotrophins that promote tissue recovery. In this work, we investigated the neuroprotective effects of GH in cultured hippocampal neurons exposed to hypoxia-ischemia injury and further reoxygenation. Hippocampal cell cultures obtained from chick embryos were incubated under oxygen-glucose deprivation (OGD, <5% O2, 1 g/L glucose) conditions for 24 h and simultaneously treated with GH. Then, cells were either collected for analysis or submitted to reoxygenation and normal glucose incubation conditions (OGD/R) for another 24 h, in the presence of GH. Results showed that OGD injury significantly reduced cell survival, the number of cells, dendritic length, and number of neurites, whereas OGD/R stage restored most of those adverse effects. Also, OGD/R increased the mRNA expression of several synaptogenic markers (i.e., NRXN1, NRXN3, NLG1, and GAP43), as well as the growth hormone receptor (GHR). The expression of BDNF, IGF-1, and BMP4 mRNAs was augmented in response to OGD injury, and exposure to OGD/R returned it to normoxic control levels, while the expression of NT-3 increased in both conditions. The addition of GH (10 nM) to hippocampal cultures during OGD reduced apoptosis and induced a significant increase in cell survival, number of cells, and doublecortin immunoreactivity (DCX-IR), above that observed in the OGD/R stage. GH treatment also protected dendrites and neurites during OGD, inducing plastic changes reflected in an increase and complexity of their outgrowths during OGD/R. Furthermore, GH increased the expression of NRXN1, NRXN3, NLG1, and GAP43 after OGD injury. GH also increased the BDNF expression after OGD, but reduced it after OGD/R. Conversely, BMP4 was upregulated by GH after OGD/R. Overall, these results indicate that GH protective actions in the neural tissue may be explained by a synergic combination between its own effect and that of other local neurotrophins regulated by autocrine/paracrine mechanisms, which together accelerate the recovery of tissue damaged by hypoxia-ischemia.

RyR-mediated Ca2+ release elicited by neuronal activity induces nuclear Ca2+ signals, CREB phosphorylation, and Npas4/RyR2 expression.

The expression of several hippocampal genes implicated in learning and memory processes requires that Ca2+ signals generated in dendritic spines, dendrites, or the soma in response to neuronal stimulation reach the nucleus. The diffusion of Ca2+ in the cytoplasm is highly restricted, so neurons must use other mechanisms to propagate Ca2+ signals to the nucleus. Here, we present evidence showing that Ca2+ release mediated by the ryanodine receptor (RyR) channel type-2 isoform (RyR2) contributes to the generation of nuclear Ca2+ signals induced by gabazine (GBZ) addition, glutamate uncaging in the dendrites, or high-frequency field stimulation of primary hippocampal neurons. Additionally, GBZ treatment significantly increased cyclic adenosine monophosphate response element binding protein (CREB) phosphorylation-a key event in synaptic plasticity and hippocampal memory-and enhanced the expression of Neuronal Per Arnt Sim domain protein 4 (Npas4) and RyR2, two central regulators of these processes. Suppression of RyR-mediated Ca2+ release with ryanodine significantly reduced the increase in CREB phosphorylation and the enhanced Npas4 and RyR2 expression induced by GBZ. We propose that RyR-mediated Ca2+ release induced by neuronal activity, through its contribution to the sequential generation of nuclear Ca2+ signals, CREB phosphorylation, Npas4, and RyR2 up-regulation, plays a central role in hippocampal synaptic plasticity and memory processes.

zapERtrap: A light-regulated ER release system reveals unexpected neuronal trafficking pathways.

Here we introduce zapalog-mediated endoplasmic reticulum trap (zapERtrap), which allows one to use light to precisely trigger forward trafficking of diverse integral membrane proteins from internal secretory organelles to the cell surface with single cell and subcellular spatial resolution. To demonstrate its utility, we use zapERtrap in neurons to dissect where synaptic proteins emerge at the cell surface when processed through central (cell body) or remote (dendrites) secretory pathways. We reveal rapid and direct long-range trafficking of centrally processed proteins deep into the dendritic arbor to synaptic sites. Select proteins were also trafficked to the plasma membrane of the axon initial segment, revealing a novel surface trafficking hotspot. Proteins locally processed through dendritic secretory networks were widely dispersed before surface insertion, challenging assumptions for precise trafficking at remote sites. These experiments provide new insights into compartmentalized secretory trafficking and showcase the tunability and spatiotemporal control of zapERtrap, which will have broad applications for regulating cell signaling and function.

Wnt5a modulates dendritic spine dynamics through the regulation of Cofilin via small Rho GTPase activity in hippocampal neurons.

Dendritic spines are small, actin-rich protrusions that act as the receiving sites of most excitatory inputs in the central nervous system. The remodeling of the synapse architecture is mediated by actin cytoskeleton dynamics, a process precisely regulated by the small Rho GTPase family. Wnt ligands exert their presynaptic and postsynaptic effects during formation and consolidation of the synaptic structure. Specifically, Wnt5a has been identified as an indispensable synaptogenic factor for the regulation and organization of the postsynaptic side; however, the molecular mechanisms through which Wnt5a induces morphological changes resulting from actin cytoskeleton dynamics within dendritic spines remain unclear. In this work, we employ primary rat hippocampal cultures and HT22 murine hippocampal neuronal cell models, molecular and pharmacological tools, and fluorescence microscopy (laser confocal and epifluorescence) to define the Wnt5a-induced molecular signaling involved in postsynaptic remodeling mediated via the regulation of the small Rho GTPase family. We report that Wnt5a differentially regulates the phosphorylation of Cofilin in neurons through both Ras-related C3 botulinum toxin substrate 1 and cell division cycle 42 depending on the subcellular compartment and the extracellular calcium levels. Additionally, we demonstrate that Wnt5a increases the density of dendritic spines and promotes their maturation via Ras-related C3 botulinum toxin substrate 1. Accordingly, we find that Wnt5a requires the combined activation of small Rho GTPases to increase the levels of filamentous actin, thus promoting the stability of actin filaments. Altogether, these results provide evidence for a new mechanism by which Wnt5a may target actin dynamics, thereby regulating the subsequent morphological changes in dendritic spine architecture.

Synaptic activity controls autophagic vacuole motility and function in dendrites.

Macroautophagy (hereafter "autophagy") is a lysosomal degradation pathway that is important for learning and memory, suggesting critical roles for autophagy at the neuronal synapse. Little is known, however, about the molecular details of how autophagy is regulated with synaptic activity. Here, we used live-cell confocal microscopy to define the autophagy pathway in primary hippocampal neurons under various paradigms of synaptic activity. We found that synaptic activity regulates the motility of autophagic vacuoles (AVs) in dendrites. Stimulation of synaptic activity dampens AV motility, whereas silencing synaptic activity induces AV motility. Activity-dependent effects on dendritic AV motility are local and reversible. Importantly, these effects are compartment specific, occurring in dendrites and not in axons. Most strikingly, synaptic activity increases the presence of degradative autolysosomes in dendrites and not in axons. On the basis of our findings, we propose a model whereby synaptic activity locally controls AV dynamics and function within dendrites that may regulate the synaptic proteome.

Ghrelin treatment leads to dendritic spine remodeling in hippocampal neurons and increases the expression of specific BDNF-mRNA species.

Ghrelin (Gr) is an orexigenic peptide that acts via its specific receptor, GHSR-1a distributed throughout the brain, being mainly enriched in pituitary, cortex and hippocampus (Hp) modulating a variety of brain functions. Behavioral, electrophysiological and biochemical evidence indicated that Gr modulates the excitability and the synaptic plasticity in Hp. The present experiments were designed in order to extend the knowledge about the Gr effect upon structural synaptic plasticity since morphological and quantitative changes in spine density after Gr administration were analyzed "in vitro" and "in vivo". The results show that Gr administered to hippocampal cultures or stereotactically injected in vivo to Thy-1 mice increases the density of dendritic spines (DS) being the mushroom type highly increased in secondary and tertiary extensions. Spines classified as thin type were increased particularly in primary extensions. Furthermore, we show that Gr enhances selectively the expression of BDNF-mRNA species.

Retinoid X receptor activation promotes re-myelination in a very old triple transgenic mouse model of Alzheimer's disease.

Alzheimer's disease (AD) is the main cause of dementia in the world. Studies of human AD brains show abnormalities in the white matter and reduction of myelin and oligodendrocyte markers. It has been proposed that oligodendrocyte progenitor cells (OPCs) present in the adult brain are a potential source for re-myelination, through proliferation and differentiation into mature oligodendrocytes. Bexarotene, a Retinoid X Receptor agonist, has been demonstrated to reverse behavioral deficits and to improved synaptic transmission and plasticity in murine models of AD, which was associated with the reduction of soluble Aß peptides. In the present study, we analyzed changes in the expression of oligodendrocyte lineage markers following oral administration of Bexarotene in a very old (24-month-old) triple transgenic mouse model of AD (3xTg-AD), for which early demyelination changes have been previously described. Bexarotene increased the expression of OPCs and intermediate oligodendrocyte progenitors (Olig2+ and O4+), and increased the number of mitotic (O4+) and myelinating mature (MBP+) oligodendrocytes. We clearly show that Bexarotene promotes re-myelination which might be important for the previously observed cognitive improvement of 3xTg-AD mice treated with this drug.

Experimental Pulmonary Tuberculosis in the Absence of Detectable Brain Infection Induces Neuroinflammation and Behavioural Abnormalities in Male BALB/c Mice.

Tuberculosis (TB) is a chronic infectious disease in which prolonged, non-resolutive inflammation of the lung may lead to metabolic and neuroendocrine dysfunction. Previous studies have reported that individuals coursing pulmonary TB experience cognitive or behavioural changes; however, the pathogenic substrate of such manifestations have remained unknown. Here, using a mouse model of progressive pulmonary TB, we report that, even in the absence of brain infection, TB is associated with marked increased synthesis of both inflammatory and anti-inflammatory cytokines in discrete brain areas such as the hypothalamus, the hippocampal formation and cerebellum accompanied by substantial changes in the synthesis of neurotransmitters. Moreover, histopathological findings of neurodegeneration and neuronal death were found as infection progressed with activation of p38, JNK and reduction in the BDNF levels. Finally, we perform behavioural analysis in infected mice throughout the infection, and our data show that the cytokine and neurochemical changes were associated with a marked onset of cognitive impairment as well as depressive- and anxiety-like behaviour. Altogether, our results suggest that besides pulmonary damage, TB is accompanied by an extensive neuroinflammatory and neurodegenerative state which explains some of the behavioural abnormalities found in TB patients.

Knockdown of lncRNA TUG1 inhibits hippocampal neuronal apoptosis and participates in aerobic exercise-alleviated vascular cognitive impairment.

OBJECTIVES: Our previous study indicated that aerobic exercise relieves cognitive impairment in patients with vascular cognitive impairment (VCI) via regulating brain-derived neurotrophic factor (BDNF), but the mechanism is not yet clear. This study aimed to explore whether lncRNA taurine upregulated gene 1 (TUG1) participates in the process of VCI by regulating BDNF. METHODS: The expressions of TUG1 and BDNF in the serum of VCI patients were detected. The potential molecular mechanisms of TUG1 in regulating hippocampal neuronal apoptosis were explored in oxygen and glucose deprivation-induced (OGD-induced) hippocampal cell line HT22. The VCI mouse model was established, and TUG1 and BDNF were overexpressed via lentivirus injection. The cognitive impairment of mice was detected by the Morris water maze experiment after the aerobic exercise. RESULTS: The level of TUG1 was elevated in the serum of VCI patients compared with the control group. The knockdown of TUG1 in OGD-induced HT22 cells increased BDNF level and decreased cell apoptosis, and the downregulation of BDNF restored the decreased cell apoptosis. RNA immunoprecipitation and RNA pull-down assays showed that TUG1 could bind to BDNF protein. The aerobic exercise alleviated cognitive impairment and inhibited hippocampal apoptosis in VCI mice. Meanwhile, the overexpression of TUG1 reversed the therapeutic effects of aerobic exercise on cognitive impairment. CONCLUSIONS: The knockdown of TUG1 reduced hippocampal neuronal apoptosis and participates in the aerobic exercise-alleviated VCI, which was partly through regulating BDNF.

LncRNA SNHG14 promotes OGD/R-induced neuron injury by inducing excessive mitophagy via miR-182-5p/BINP3 axis in HT22 mouse hippocampal neuronal cells.

BACKGROUND: Long non-coding RNA (lncRNA) small nucleolar RNA host gene 14 (SNHG14) is associated with cerebral ischemia-reperfusion (CI/R) injury. This work aims to explore the role of SNHG14 in CI/R injury. METHODS: HT22 (mouse hippocampal neuronal cells) cell model was established by oxygen-glucose deprivation/reoxygenation (OGD/R) treatment. The interaction among SNHG14, miR-182-5p and BNIP3 was verified by luciferase reporter assay. Flow cytometry, western blot and quantitative real-time PCR were performed to examine apoptosis, the expression of genes and proteins. RESULTS: SNHG14 and BNIP3 were highly expressed, and miR-182-5p was down-regulated in the OGD/R-induced HT22 cells. OGD/R-induced HT22 cells exhibited an increase in apoptosis. SNHG14 overexpression promoted apoptosis and the expression of cleaved-caspase-3 and cleaved-caspase-9 in the OGD/R-induced HT22 cells. Moreover, SNHG14 up-regulation enhanced the expression of BNIP3, Beclin-1, and LC3II/LC3I in the OGD/R-induced HT22 cells. Furthermore, SNHG14 regulated BNIP3 expression by sponging miR-182-5p. MiR-182-5p overexpression or BNIP3 knockdown repressed apoptosis in OGD/R-induced HT22 cells, which was abolished by SNHG14 up-regulation. CONCLUSION: Our study demonstrates that lncRNA SNHG14 promotes OGD/R-induced neuron injury by inducing excessive mitophagy via miR-182-5p/BINP3 axis in HT22 mouse hippocampal neuronal cells. Thus, SNHG14/miR-182-5p/BINP3 axis may be a valuable target for CI/R injury therapies.

Memory and dendritic spines loss, and dynamic dendritic spines changes are age-dependent in the rat.

Brain aging is a widely studied process, but due to its complexity, much of its progress is unknown. There are many studies linking memory loss and reduced interneuronal communication with brain aging. However, only a few studies compare young and old animals. In the present study, in male rats aged 3, 6, and 18 months, we analyzed the locomotor activity and also short and long-term memory using the novel object recognition test (NORT), in addition to evaluating the dendritic length and the number of dendritic spines in the prefrontal cortex (PFC) and in the CA1, CA3 and DG regions of the dorsal hippocampus using Golgi-Cox staining. We also analyzed the types of dendritic spines in the aforementioned regions. 6- and 18-month old animals showed a reduction in locomotor activity, while long-term memory deficit was observed in 18-month old rats. At 18 months old, the dendritic length was reduced in all the studied regions. The dendritic spine number was also reduced in layer 5 of the PFC, and the CA1 and CA3 of the hippocampus. The dynamics of dendritic spines changed with age, with a reduction of the mushroom spines in all the studied regions, with an increase of the stubby spines in all the studied regions except from the CA3 region, that showed a reduction. Our data suggest that age causes changes in behavior, which may be the result of morphological changes at the dendrite level, both in their length and in the dynamics of their spines.

Association of electroanalytical and spectrophotometric methods to evaluate the antioxidant activity of isobenzofuranone in primary cultures of hippocampal neurons.

The isobenzofuran-1(3H)-ones (phthalides) exhibit various biological activities, including antioxidant activity on reactive oxygen species (ROS). An excess of ROS that cannot be naturally contained by cellular enzymatic systems is called redox imbalance, which damage cell membranes, proteins, and DNA, thereby possibly triggering neuronal death in several neurodegenerative diseases. Considering our ongoing efforts to find useful compounds to control redox imbalance, herein we evaluated the antioxidant activity of two phtalides (compounds 3 and 4), using primary cultures of hippocampal neurons. Spectrophotometric assays showed that compound 3 significantly reduced (p ≤ 0.05) ROS levels and lipid peroxidation compared to the control treatment, while compound 4 was unable at any of the tested concentrations. Despite their structural similarity, these compounds behave differently in the intracellular environment, which was reliably corroborated by the determination of oxidation potentials via cyclic voltammetry. It was demonstrated that compound 3 presents a lower oxidation potential. The combination of the mentioned methods allowed us to find a strong correlation between the chemical structure of compounds and their biological effects. Taking together, the results indicate that compound 3 presents desirable characteristics to act as a candidate pharmacological agent for use in the prevention and treatment of neurodegenerative diseases.

Guanosine Promotes Proliferation in Neural Stem Cells from Hippocampus and Neurogenesis in Adult Mice.

Neural stem cells can generate new neurons in the mouse adult brain in a complex multistep process called neurogenesis. Several factors regulate this process, including neurotransmitters, hormones, neurotrophic factors, pharmacological agents, and environmental factors. Purinergic signaling, mainly the adenosinergic system, takes part in neurogenesis, being involved in cell proliferation, migration, and differentiation. However, the role of the purine nucleoside guanosine in neurogenesis remains unclear. Here, we examined the effect of guanosine by using the neurosphere assay derived from neural stem cells of adult mice. We found that continuous treatment with guanosine increased the number of neurospheres, neural stem cell proliferation, and neuronal differentiation. The effect of guanosine to increase the number of neurospheres was reduced by removing adenosine from the culture medium. We next traced the neurogenic effect of guanosine in vivo. The intraperitoneal treatment of adult C57BL/6 mice with guanosine (8 mg/kg) for 26 days increased the number of dividing bromodeoxyuridine (BrdU)-positive cells and also increased neurogenesis, as identified by measuring doublecortin (DCX)-positive cells in the dentate gyrus (DG) of the hippocampus. Antidepressant-like behavior in adult mice accompanied the guanosine-induced neurogenesis in the DG. These results provide new evidence of a pro-neurogenic effect of guanosine on neural stem/progenitor cells, and it was associated in vivo with antidepressant-like effects.

Changes in hippocampal astrocyte morphology of Ruddy turnstone (Arenaria interpres) during the wintering period at the mangroves of Amazon River estuary.

Astrocytes are essential for lipid neuronal metabolism in long-distance uninterrupted migratory flights, when glucose is not available as the main source of energy. We previously demonstrated in Calidris pusilla that after uninterrupted 5 days transatlantic flight, astrocytes shrink and reduce its number in the hippocampal formation. Here we shifted our attention to the wintering period and tested the hypothesis that hippocampal astrocyte morphology of A interpres will change as the wintering period progresses towards the premigration window. To that end we used Arenaria interpres, which also crosses the Atlantic Ocean and reaches the mangroves of the Amazon River estuary for wintering. Birds were captured in September/October (closer to the arrival in the coast of Bragança, Para, Brazil for wintering) and in April/May (closer to the departure towards the breeding sites) and had their brains processed for selective GFAP-astrocyte immunolabeling. Three-dimensional reconstructions of the immunostained astrocytes were performed and morphological classification was done based on hierarchical cluster and discriminant analysis of multimodal morphometric features. We found two morphological phenotypes of astrocytes in the newcomers which differentially increased its morphological complexities as wintering period progresses towards the pre-migration window. Taken together, our findings demonstrate that the long-distance non-stop flight and wintering period differentially affected the two astrocytes morphotypes, suggesting distinct physiological roles for these cells. We suggest that morphological changes during the wintering period, may be part of the adaptive plasticity of the local hippocampal circuits of A. interpres in preparation for the long journey back to their breeding sites in the north hemisphere.