Hippocampal neurogenesis continues throughout life in mammals. These adult-generated dentate granule cells (DGCs) are generally believed to contribute to hippocampal memory processing and are generated at varying rates in response to neuronal network activity. Deep brain stimulation (DBS) allows clinicians to influence brain activity for therapeutic purposes and raises the possibility of targeted modulation of adult hippocampal neurogenesis. It has recently been shown that DBS may ameliorate cognitive decline associated with Alzheimer’s disease (AD), and while underlying mechanisms are unknown, one possibility is activity-dependent regulation of hippocampal neurogenesis. To this end, whether or not adult-generated DGCs can assume functional roles of developmentally-generated neurons, and stimulation-induced enhanced neurogenesis can benefit memory function in the normal and diseased brain, warrant study. First, we examined separate cohorts of developmentally- and adult-generated DGCs in intact mice and demonstrated similar rates of activation during hippocampus-dependent spatial memory processing, suggesting functional equivalence. Second, we examined the neurogenic and cognitive effects of targeted entorhinal cortex (EC) stimulation in mice using parameters analogous to clinical high frequency DBS. Stimulation increased the generation of DGCs. Moreover, stimulation-induced neurons were functionally recruited by hippocampal spatial memory processing in a cell age-dependent fashion that is consistent with DGC maturation. Importantly, stimulation facilitated spatial memory in the same maturation-dependent manner, and not when stimulation-induced promotion of adult neurogenesis was blocked, suggesting a causal relationship. Finally, we are in the process of testing whether similar stimulation facilitates spatial memory in a transgenic (Tg) disease model of AD that exhibits amyloid neuropathology and cognitive impairment. Preliminary results suggest stimulation promotes neurogenesis and rescues impaired spatial memory in Tg animals. When considered in the context of promising clinical results, this body of work suggests stimulation-induced neurogenesis could provide a novel therapeutic modality in settings where functional hippocampal regenerative therapy is desirable.

No description available.

<p>It is commonly accepted that aerobic exercise increases hippocampal neurogenesis, learning and memory, as well as stress resiliency. However, human populations are widely variable in their inherent aerobic fitness as well as their capacity to show increased aerobic fitness following a period of regimented exercise. It is unclear whether these inherent or acquired components of aerobic fitness play a role in neurocognition. To isolate the potential role of inherent aerobic fitness, we exploited a rat model of high (HCR) and low (LCR) inherent aerobic capacity for running. At a baseline, HCR rats have two- to three-fold higher aerobic capacity than LCR rats. We found that HCR rats also had two- to three- fold more young neurons in the hippocampus than LCR rats as well as rats from the heterogeneous founder population. We then asked whether this enhanced neurogenesis translates to enhanced hippocampal cognition, as is typically seen in exercise-trained animals. Compared to LCR rats, HCR rats performed with high accuracy on tasks designed to test neurogenesis-dependent pattern separation ability by examining investigatory behavior between very similar objects or locations. To investigate whether an aerobic response to exercise is required for exercise-induced changes in neurogenesis and cognition, we utilized a rat model of high (HRT) and low (LRT) aerobic response to treadmill training. At a baseline, HRT and LRT rats have comparable aerobic capacity as measured by a standard treadmill fit test, yet after a standardized training regimen, HRT but not LRT rats robustly increase their aerobic capacity for running. We found that sedentary LRT and HRT rats had equivalent levels of hippocampal neurogenesis, but only HRT rats had an elevation in the number of young neurons in the hippocampus following training, which was positively correlated with accuracy on pattern separation tasks. Taken together, these data suggest that a significant elevation in aerobic capacity is necessary for exercise-induced hippocampal neurogenesis and hippocampal neurogenesis-dependent learning and memory. To investigate the potential for high aerobic capacity to be neuroprotective, doxorubicin chemotherapy was administered to LCR and HCR rats. While doxorubicin induces a progressive decrease in aerobic capacity as well as neurogenesis, HCR rats remain at higher levels on those measures compared to even saline-treated LCR rats. HCR and LCR rats that received exercise training throughout doxorubicin treatment demonstrated positive effects of exercise on aerobic capacity and neurogenesis, regardless of inherent aerobic capacity. Overall, these findings demonstrate that inherent and acquired components of aerobic fitness play a crucial role not only in the cardiorespiratory system but also the fitness of the brain.</p> / Dissertation

Fragile X Syndrome (FXS) is the most common form of inherited mental retardation, affecting approximately 1/4000 males and 1/6000 females worldwide. FXS is caused by loss of FMR1 gene expression, resulting in the lack of the protein product, Fragile X protein (FMRP). FMRP is an RNA-binding protein thought to regulate synaptic plasticity by controlling the localization and translation of specific mRNAs in neurons. To determine whether FMRP is also required in early brain development we examined the distribution of cell cycle markers in Drosophila FMR1 (dFmr1) mutant brains compared to wild-type brains. Our results indicate that the loss of dFmr1 leads to a significant increase in the number of mitotic neuroblasts and BrdU incorporation in the brain, consistent with the notion that FMRP controls proliferation in neural stem cells. To determine the role of FMRP in neuroblast division and differentiation, we used Mosaic Analysis with a Repressible Marker (MARCM) approaches in the developing larval brain and found that single dFmr1 neuroblasts generate significantly more neurons than controls. Developmental studies suggest that FMRP also inhibits neuroblast exit from quiescence, or reactivation, in early larval brains, as indicated by misexpression of the G1 to S phase transition marker Cyclin E. We have also identified a novel role for FMRP in the glia surrounding the neuroblasts, indicating that FMRP in these cells contributes to the regulation of neuroblast reactivation via signaling from the supporting glial cells. Our results demonstrate that FMRP is required during brain development to control the exit from quiescence and proliferative capacity of neuroblasts as well as neuron production, which may provide insights into Fragile X Syndrome and other Autism-Spectrum disorders.

The present study examined social status and adult neurogenesis in the naked mole rat. These animals live in large colonies with a strict reproductive dominance hierarchy; one female and 1-3 males breed, while other members are subordinate and reproductively suppressed. We examined whether social status affects doublecortin (DCX; a marker for immature neurons) immunoreactivity in the dentate gyrus, piriform cortex (PCx), and basolateral amygdala (BLA) by comparing breeders to subordinates. We also examined subordinates removed from their colony and paired with opposite- or same-sex conspecifics for 6 months. Breeders had reduced DCX immunoreactivity in all areas, with BLA effects confined to females. Effects of housing condition were region-specific, with higher PCx DCX immunoreactivity observed in opposite- than same-sex paired subordinates regardless of gonadal status. The opposite pattern was observed in the BLA. Future work will clarify whether findings are attributable to status differences in stress, behavioural plasticity, or life stage.

The neocortex is the most recently evolved part of the mammalian brain which is involved in a repertoire of higher order brain functions, including those that separate humans from other animals. Humans have evolved an expanded neocortex over the course of evolution through a massive increase in neuron number (compared to our close relatives-­‐‑ the chimpanzees) in spite of sharing similar gestation time frames. So what do humans do differently compared to chimpanzees within the same time frame during their development? This dissertation addresses this question by comparing the developmental progression of neurogenesis between humans and chimpanzees using cerebral organoids as the model system. The usage of cerebral organoids, has enabled us to compare the development of both the human neocortex, and the chimpanzee neocortex from the very initiation of the neural phase of embryogenesis until very long periods of time. The results obtained so far suggest that the genetic programs underlying the development of the chimpanzee neocortex and the human neocortex are not very different, but rather the difference lies in the timing of the developmental progression. These results show that the chimpanzee neocortex spends lesser time in its proliferation phase, and allots lesser time to the generation of its neurons than the human neocortex. In more scientific terms, the neurogenic phase of the neocortex is shorter in chimpanzees than it is in humans. This conclusion is supported by (1) an earlier onset of gliogenesis in chimpanzees compared to humans which is indicative of a declining neurogenic phase, (2) an earlier increase in the chimpanzee neurogenic progenitors during development, compared to humans, (3) a higher number of stem cell– like progenitors in human cortices compared to chimpanzees, (4) a decline in neurogenic areas within the chimpanzee cerebral organoids over time compared to human cerebral organoids.

Les vertébrés, du poisson à l'homme, possèdent un potentiel membranaire médié en partie par les ions chlorure (Cl-). L’une des premières formes d’activité neuronale lors du développement est la dépolarisation médiée par les ions chlorures extrudés par les canaux glycinergiques (GlyR) et GABAergiques. Cette dépolarisation est rendu possible grâce à l’expression retardée du co-transporteur d’ions chlorure et de potassium KCC2 lors du développement qui génère un gradient hyperpolarisant postnatalement chez les mammifères. Le rôle de cette dépolarisation précoce paradoxale durant le développement est inconnu. En injectant l’ARNm de KCC2 dans des embryons de poissons zébrés nouvellement fertilisé, nous avons devancé l’expression de ce co-transporteur rendant ainsi la glycine hyperpolarisante dans tous les neurones dès les premières phases du développement. Nous avons aussi ciblé le récepteur glycinergique directement en bloquant son activité et son expression à l’aide d’une drogue spécifique, la strychnine et d’un morpholino antisens (Knockdown). Dans les trois cas (KCC2, strychnine et GlyR KD), les perturbations de l’activité neuronale ont provoqués des erreurs dans la neurogenèse, en particulier une diminution du nombre d’interneurones sans avoir d’effets sur les motoneurones et les neurones sensoriels. De plus, en bloquant les canaux calciques activés à bas voltage dans le développement avec la drogue nifedipine, il y a des erreurs dans la neurogénèse semblables à celles remarquées dans les trois conditions précédentes. Nous concluons que la dépolarisation précoce par la glycine permet l’entrée du calcium et l’activation de la neurogénèse chez les interneurones. / Vertebrates, from fish to man, have a membrane potential mediated in part by chloride ions (Cl-). One of the first neuronal activity during development of the zebrafish spinal cord is cell depolarisation mediated by chloride extrusion via glycinergic receptors (GlyRs) and GABAergic receptors. This depolarisation is due to the absence of chloride-potassium cotransport channel KCC2, whose expression comes later in development, creating a hyperpolarising gradient. The role of this paradoxal depolarisation period during early stages of development is still unknown. By injecting KCC2 mRNA in newly fertilised zebrafish embryos, we expressed this co-transporter channel in neurons causing glycine to hyperpolarize in early phases of development. We also directly targeted the glycine receptor (GlyR) itself by blocking its activation with a chronic treatment of Strychnine, a specific drug, and by knocking down the expression of this receptor with an antisense morpholino injection. In those three conditions (KCC2, Strychnine and GlyR KD), perturbation of neuronal activity provoked major defects in neurogenesis, particulary in development of interneurons, without affecting other types of cells like motoneurons and sensory neurons. In addition, blocking low-voltage activated calcium channels with nifedipine provoked similar phenotypes. We conclude that the early glycine-mediated depolarisation allow calcium entry, thus activating certain aspects of interneurons neurogenesis.

Stress-related psychological ill health has increased dramatically in Europe. A diagnosis equivalent to occupational burnout can be found in the Swedish version of the tenth edition of the “International Statistical Classification of Diseases and Related Health Problems" by the World Health Organization. The Swedish National Board of Health and Welfare lists treatment suggestions including a section of self-care that recommended something that could be translated to “a sensible diet” (“vettig kost”) without providing evidence for what could constitute a sensible diet. By using the hypothesis of burnout being a stress-mediated decrease in neurogenesis which in turn decrease the ability to cope with stress, this article systematically reviews the efficacy of dietary polyphenols on neurogenesis in rodents to evaluate if dietary polyphenols could constitute a part of a sensible diet for burnout patients. Dietary polyphenols significantly increased various parts of neurogenesis, in rodents subjected to stressors, in some cases demonstrating effect sizes comparable to antidepressants. Adverse effects have been observed in extremely high doses and young rodents not exposed to induced stressors with a putative high level of neurogenesis.

As epilepsias acometem entre 1-2% da população mundial. De um modo geral, de todas as epilepsias quase um terço deste total de pacientes apresenta a síndrome epiléptica conhecida como Epilepsia de Lobo Temporal (ELT), a qual se instala geralmente após um insulto inicial ou em decorrência de outras patologias como, por exemplo, trauma ou tumor, e parece ser decorrente de anormalidades intrínsecas do lobo temporal tais como, amígdala, hipocampo e córtex piriforme. Depois de um período de latência variado, promove o surgimento de crises convulsivas. Dentre os pacientes que apresentam ELT, cerca de 20 a 30% deles apresentam resistência ao tratamento farmacológico. Para melhor estudar os processos plásticos envolvidos no processo de epileptogênese ocorridos após a instalação do insulto inicial que levam ao aparecimento de crises recorrentes espontâneas, ratos Wistar foram eletricamente estimulados na amígdala para indução de Status Epilepticus (SE). Foram feitas histoquímicas e immunohistoquímica para marcar neurônios ativados (c-Fos+), novos neurônios (Doublecortin DCX+) e em degeneração (FluoroJade C - FJC+) após as crises. Após a indução do SE observamos que quanto mais graves as crises, maior o número de áreas ativadas (c-Fos+) e maior número de neurônios em degeneração (FJC+). Além disso, não houve associação direta entre as áreas cerebrais ativadas e grau de neurodegeneração, nem associação entre gravidade do SE e intensidade de neurogênese (DCX). A segunda fase deste projeto, executada na University of Cincinnati, refere-se ao estudo do impacto do SE, induzido por pilocarpina (PILO) sistêmica, sobre a neurogênese hipocampal. Utilizando a injeção de BrdU, para marcar o dia do nascimento de novos neurônios granulares, em camundongos Thy1-GFP foram submetidos ao SE por PILO. Foram analisadas a plasticidade dendrítica de neurônios granulares em fase de maturação (imaturas, 1 semana) e maduras (8 semanas). As células imaturas sofreram drásticas modificações na sua morfologia e na densidade dendrítica. Por outro lado, as células maturas não sofreram alterações morfológicas na árvore dendrítica, mas apresentaram uma intensa redução na densidade dos espinhos dendríticos, mostrando assim que as células imaturas estão mais suceptíveis ao impacto das crises epilépticas. / The epilepsies affect between 1-2% of the world. In general, all epilepsies almost a third of total patients had an epilepsy syndrome known as temporal lobe epilepsy (TLE), which usually settles after the initial insult or due to other pathologies such as, for example, trauma or tumor, and seems to be due to intrinsic abnormalities such as temporal lobe, amygdala, hippocampus and piriform cortex. After latency period varied, promotes the emergence of seizures. Among the patients with TLE, about 20 to 30% of them are resistant to pharmacological treatment. To better study the processes involved in plastic epileptogenesis occurred after the installation of the initial insult leading to the appearance of spontaneous recurrent seizures, rats were electrically stimulated in the amygdala to induce status epilepticus (SE). Histochemical and immunohistochemistry were done to mark neurons activated (c-Fos +), newborn neurons (Doublecortin - DCX+) and degenerating (FluoroJade C - FJC+) after the crisis. After SE induction observed that the more serious crises, the greater the number of activated areas (c-Fos+) and greater number of degenerating neurons (FJC+). In addition, there was no direct association between the brain areas activated and the degree of neurodegeneration, or association between the severity and intensity of the SE of neurogenesis (DCX+). The second phase of this project, performed at the University of Cincinnati, refers to study the impact of SE induced by pilocarpine (Pilo) system on hippocampal neurogenesis. Using the injection of BrdU, to label the daybirth of new granule neurons in Thy1-GFP mice subjected to SE. We analyzed the dendritic plasticity of granule neurons undergoing maturation (immature, 1 week) and mature (8 weeks). The immature cells have undergone drastic changes in their dendritic morphology and density. On the other hand, the mature cells did not undergo morphological changes in dendritic tree but showed a marked decrease in the density of dendritic spines, thus showing that immature cells are more susceptible to the impact of epileptic seizures.

O conhecimento atual sugere que a neurogênese adulta é um mecanismo de plasticidade importante para a manutenção da homeostasia cerebral e conservado no cérebro de mamíferos. A neurogênese adulta pode ser modulada negativamente por exposição prolongada ao estresse e positivamente por fármacos antidepressivos. Nesse sentido, utilizamos o modelo de estresse crônico imprevisível (CUS) para mimetizar em animais o impacto da exposição crônica ao estresse sobre o comportamento e sobre a neurogênese adulta. A administração crônica de antidepressivos pode atenuar o aparecimento de respostas comportamentais em animais submetidos ao CUS, embora exista uma considerável latência para o surgimento desses efeitos. Recentemente, o canabidiol (CBD) emergiu como um novo fármaco com potencial terapêutico para tratamento de transtornos psiquiátricos, como a ansiedade e capaz de reduzir a latência para início dos efeitos em relação aos antidepressivos clássicos, sendo os mecanismos até então pouco compreendidos. Portanto, o objetivo deste trabalho foi investigar se o tratamento com CBD ou escitalopram (ESC) durante 7 ou 14 dias é capaz de atenuar respostas comportamentais do tipo ansiogênica em animais submetidos ao CUS e observar se esse efeito poderia correlacionar-se a diferentes mecanismos relacionados à neurogênese adulta. Para isso, camundongos C57BL/6 machos foram divididos em 6 grupos. Os animais de cada grupo receberam somente um tratamento: CBD (30mg/Kg), ESC (20mg/Kg) ou veículo diariamente durante 7 (n=9-10=grupo) ou 14 dias (n=6-10/grupo) de maneira independente e foram submetidos ou não ao CUS durante o mesmo período. Um dia após o último tratamento, os animais foram submetidos ao teste do Novelty Supressed Feeding (NSF). Além disso, foram realizadas análises de proliferação celular (Ki67), da sobrevivência celular (BrdU) e de marcadores associados a distintos tipos celulares (Sox2 e DCX). Os resultados obtidos no presente trabalho sugerem que o CBD é capaz de prevenir os efeitos do estresse crônico em protocolos de 7 e 14 dias de tratamento, enquanto que o antidepressivo escitalopram previne os efeitos do estresse apenas no protocolo de 14 dias. Além disso, o estresse não alterou significativamente a taxa de sobrevivência celular em ambos protocolos, mas promoveu redução da proliferação celular em 7 dias. Além disso, observou-se uma redução do número de células DCX+ no grupo dos animais estressados/veículo em relação ao grupo de animais controle/veículo no protocolo de 7 dias, diferença esta não encontrada no protocolo de 14 dias. Com relação ao efeito dos tratamentos, encontramos que o CBD ou ESC não previnem a redução da proliferação celular mediada pelo estresse, mas previnem a redução de células DCX+ no protocolo de 7 dias. Os resultados encontrados no presente trabalho sugerem que o CBD pode prevenir os efeitos do estresse em um menor período de tempo quando comparado ao ESC. Porém, o presente trabalho não demonstrou alteração significativa nos parâmetros relacionados à neurogênese, tampouco modulação diferencial entre os fármacos / Current knowledge suggests that adult neurogenesis is an important plasticity mechanism for the maintenance of cerebral homeostasis and conserved in the mammalian brain. Adult neurogenesis can be modulated negatively by prolonged exposure to stress and positively by antidepressant drugs. In the present study, we expose mice to the unpredictable chronic stress paradigm (CUS) and evaluated the impact of chronic exposure to stress on behavior. Chronic administration of antidepressants attenuate CUS-induced behavioral abnormalities in animals, although there is a considerable latency for the appearance of the effects of these drugs. Recently, cannabidiol (CBD) has emerged as a putative new drug with for the treatment of psychiatric disorders, such as anxiety. Therefore, the objective of this study was to investigate whether the treatment with CBD or escitalopram (ESC) for 7 or 14 days is able to attenuate CUS-induced anxiogenic response in mice and, if its effects are correlated with mechanism involving adul type in animals submitted to the CUS and to observe if this effect could correlate to different related mechanisms to adult neurogenesis. Male C57BL6 mice were divided in 6 groups. Each animal of every experimental group received: CBD (30mg / kg), ESC (20mg / kg) or vehicle daily for 7 (n = 9-10 = group) or 14 days (n = 6-10 / group) and were submitted or not to the CUS during the same period. One day after the last treatment, animals were submitted to the Novelty Supressed Feeding (NSF) test. In addition, analyzes of cell proliferation (Ki67), cell survival (BrdU) and markers associated with different cell types (Sox2 and DCX) were performed. The results obtained in the present work suggest that CBD is able to prevent the effects of chronic stress in protocols of 7 and 14 days of treatment, whereas the antidepressant escitalopram prevents the effects of stress only in the protocol of 14 days. In addition, stress did not significantly alter the rate of cell survival in both protocols, but promoted reduction of cell proliferation in 7 days. In addition, a reduction in the number of DCX + cells in the group of stressed animals / vehicle was observed in relation to the group of control / vehicle animals in the 7-day protocol, a difference not found in the 14-day protocol. Regarding the effect of treatments, we found that CBD or ESC did not prevent the reduction of cell proliferation mediated by stress, but prevented the reduction of DCX + cells in the 7-day protocol. The results found in the present study suggest that CBD can prevent the effects of stress in a shorter window when compared to ESC. These effects however seem not to be related to adult hippocampal neurogenesis