Entre os PRRs (receptores de reconhecimento padrão), NOD-like receptors (NLRs), tal como NOD2, são responsáveis pela detecção intracelular de muramil dipeptídeo (MDP); padrão molecular associado a patógeno (PAMP), encontrado no peptidoglicano (PGN) de praticamente todas bactérias GRAM positiva e negativa. Após o reconhecimento e estimulação por MDP, NOD2 recruta diretamente a serina-treonina quinase RIPK2, uma proteína adaptadora importante na ativação de NF?B mediada por NOD2. A expressão de NOD2 foi descrita em macrófagos e em outras células. Além disso, trabalhos anteriores indicaram que PRRs desempenham papel crucial na ativação de células gliais da medula espinal, na indução e manutenção da dor inflamatória crônica e dor neuropática. No presente estudo, avaliamos o papel de NOD2 na modulação da sensibilidade à dor, focando sua importância na ativação de células da glia da medula espinal, bem como a sua via de sinalização (RIPK2) e liberação de citocinas pró-nociceptivas, como o fator de necrose tumoral alfa (TNF-?), interleucina-6 (IL-6) e interleucina-1 beta (IL-1?). Os resultados demonstram que camundongos selvagens tratados com MDP, apresentaram diminuição no limiar nociceptivo mecânico (pico entre 3 e 5 horas) comparado com o grupo controle (veículo), retornando ao basal após 48 horas. Além disso, camundongos NOD2-/- , RIPK2-/- , TNFR1/2-/- e IL-6 -/- tratados com MDP não diferiram o limiar nociceptivo mecânico, comparado com seus respectivos grupos controle (veículo). Entretanto, camundongos TNFR1- /- , CCR2-/- , TLR4-/- , MyD88-/- e TRIF-/- tratados com MDP, apresentaram diminuição no limiar nociceptivo mecânico similar aos camundongos selvagens tratados com MDP. Adicionalmente, o pré-tratamento de camundongos selvagens com IL-1ra, propentofilina, minociclina, fluorocitrato e SB 203580 inibiu o desenvolvimento da hipersensibilidade mecânica induzida por MDP. Estes dados sugerem que a ativação do sensor intracellular NOD2 esta presente em células da glia da medula espinal e estimula a ativação das vias de sinalização RIPK2 e p38 MAPK com subsequente produção de IL-1?, IL-6 e TNF?, por uma via de sinalização independente de TLR4, MyD88 e TRIF. Finalmente, estes mecanismos contribuem para o processo de hipersensibilidade mecânica durante a neuropatia periférica e representam uma nova abordagem para elucidar os mecanismos envolvidos na fisiopatologia da dor crônica. / Among PRRs (pattern recognition receptors), NOD-like receptors (NLRs), such as NOD2 are responsible by intracellular detection of muramyl dipeptide (MDP); pathogen-associated molecular pattern (PAMP) found in the peptidoglycan (PGN) from virtually all gram positive and gram negative bacteria. Upon recognition and stimulation by MDP, NOD2 recruits directly the receptor-interacting serine/threonine-protein kinase 2 (RIPK2), an adaptor protein important in the NOD2-mediated NF?B activation. The expression of NOD2 has been described in macrophages and other cells. Moreover, previous work has indicated that PRRs play a crucial role in the activation of spinal cord glial cells, in the induction and maintenance of chronic inflammatory and neuropathic pain. In the present study, we aimed to evaluate the role of NOD2 in the modulation of pain sensitivity, focusing on its importance in the activation of spinal cord glial cells, as well as its signaling pathway (RIPK2) and release of pro-nociceptive cytokines, such as tumour necrosis factor-alpha (TNF-?), interleukin-6 (IL-6) and interleukin-1beta (IL-1?). The results demonstrate that WT mice treated with MDP showed a decrease in mechanical nociceptive threshold (peak 3 to 5 hours) compared with the control group (vehicle), returning to the base line after 48 hours. Furthermore, NOD2-/- , RIPK2-/- , TNFR1/2-/- and IL-6 -/- mice treated with MDP did not differ the mechanical nociceptive threshold compared with their respective control groups (vehicle). However, TNFR1-/- , CCR2-/- , TLR4-/- , MyD88-/- and TRIF-/- mice treated MDP, showed a decrease in mechanical nociceptive threshold similar to WT mice treated with MDP. In addition, the pretreatment of WT mice with IL-1ra, propentofylline, minocycline, fluorocitrate and SB 203580 inhibited the development of mechanical hypersensitivity induced by MDP. These data suggest that activation of the intracellular sensor NOD2 present in spinal cord glial cells stimulates the activation of RIPK2 and p38 MAPK signaling pathways and subsequent production of IL-1?, IL-6 and TNF?, in a TLR4-, MyD88- and TRIF-independent signaling pathway. Finally, these mechanisms contribute to the process of mechanical hypersensitivity during peripheral neuropathy and represent a novel approach for elucidating the mechanisms underlying pathophysiology of chronic pain.

Le gène split end (spen) est impliqué dans de nombreuses voies de signalisation et processus biologiques. Durant ma thèse j'ai étudié le rôle de spen dans la mort cellulaire au cours du développement de la rétine de la Drosophile. L'œil de Drosophile est composé de centaines d'unités appelées ommatidies. Chaque ommatidie est composée de huit photorécepteurs entourés de cellules accessoires comprenant quatre cellules cônes et deux cellules pigmentaires primaires, ainsi que douze cellules interommatidiales. Les cellules interommatidiales adoptent une structure hexagonale parfaitement régulière. Des cellules interommatidiales en excès doivent être éliminées par apoptose au cours du développement. J'ai montré que la modulation de spen modifiait radicalement le patron des cellules interommatidiales. L'inactivation de spen conduit à un défaut de cellules interommatidiales alors que sa surexpression entraîne un excès de ces cellules. Ces résultats témoignent d’un rôle anti-apoptotique de spen. Nous avons aussi montré que la perte des cellules interommatidiales dans un contexte mutant pour spen pouvait être entièrement sauvée en exprimant la protéine p35 connue pour bloquer l'activité des caspases. Comme spen est exprimé de manière ubiquitaire, nous avons cherché à déterminer dans quelles cellules spen jouait son rôle de régulateur de la mort cellulaire. Grâce à une analyse clonale, nous avons pu montrer que c'est au niveau des cellules cônes que spen agit. L'inactivation de spen dans les autres cellules accessoires de l'œil n'influence pas la mort des cellules interommatidiales. Nous avons en outre, montré que spen avait un rôle dans la formation des soies de chaque ommatidie. Ces travaux mettent en évidence un rôle de spen dans le contrôle de la mort cellulaire des cellules interommatidiales dans les cellules cônes. Nos résultats montrent, par ailleurs, que spen serait requis pour le relarguage du facteur de survie Spitz (le ligand activateur de la voie EGF) à partir des cellules cônes. En parallèle, nous avons étudiés le rôle de survie de spen dans un modèle neurodégénératif. Nous avons montré que spen était nécessaire dans les cellules gliales pour la résistance au stress oxydatif. De manière intéressante, nous avons trouvé que l'inactivation de spen dans la glie diminuait l'activité de la voie de signalisation NOTCH. Cette résistance pourrait se faire via la modulation de gènes antioxydants. De manière générale, nos travaux démontrent un rôle du gène split ends dans la survie cellulaire. Ce facteur agit de manière non-autonome à partir des cellules supports de différents organes. / In metazoan, the successful development of many organs requires the elimination of supernumerary cells by apoptosis. For example, the elimination of about two thousand interommatidial cells (IOCs) during Drosophila eye development allows the precise rearrangement of ommatidia in a perfect hexagonal array. Maximal apoptosis occurs during pupal life and the remaining IOCs differentiate into secondary and tertiary pigment cells. The precise removal of unwanted IOCs requires coordinated activation of Notch (pro-death) and EGF (pro-survival) pathways. IOCs undergoing apoptosis express the IAP inhibitor Hid, which leads to the activation of initiator and effector caspases. However, the mechanisms that coordinate the death and survival pathways for timed and precise IOC removal are poorly understood.Here, we report that spen encodes a nuclear protein expressed in the pupal eye that is required for IOC survival. We showed that the inhibition of spen, by either RNAi or in spen mutant clones resulted in disorganized ommatidia with missing IOCs. Moreover, overexpression of spen leads to extra IOCs. These results indicate that spen expression promotes IOC survival during eye development. Importantly blocking apoptosis prevents the loss of IOC in a spen mutant retina. Spen is a protein known to be ubiquitous in tissue during development. Indeed, we have shown using an enhancer trap line that spen is expressed in all the cells in the eye pupal disk. To better understand where spen is acting from in this tissue to regulate cell death, we performed a clonal analysis. We found that the inactivation of spen in the cone cells was causing the loss of IOC, indicating that spen is required non-autonomously in cone cell for IOC survival. In parallel we have shown that the inactivation of spen was disrupting eye bristles morphology. Even if studies discuss the role of bristles in the regulation of developmental apoptosis in this context, our clonal analysis excluded this possibility. Furthermore, we found that spitz, the EGFR ligand, accumulate in cone cells upon spen inactivation. Our current hypothesis is that spen is likely to be required for the release of Spitz from the cone cells in order to active the survival signaling pathway EGFR in the IOCs. Also, we examined the protective role of spen in a chemical model of Parkinson disease (paraquat treatment). We showed that the glial expression of spen is protective in this context, which suggest against that spen acts non-autonomously. Interestingly we found that the inactivation of spen in glia downregulates the Notch signaling pathway. Spen is likely to be a key factor integrating cues from different signaling pathways to promote cell survival.

<p>Amyotrophic lateral sclerosis is a fatal, progressive neurodegenerative disease with unknown ethiology. The aim of this study was to increase understanding of the pathophysiological mechanisms of dying motor neurons and wasting muscle tissue in this particular disorder.</p><p>Quantitative receptor autoradiographic methodology was applied on cervical spinal cord sections from patients with ALS to evaluate the specific binding of the acetylcholine transporter ³H-vesamicol in motor neurons. Despite a significant reduction of the number of ventral motor neurons in ALS, the ³H-vesamicol binding was not reduced in ALS compared to control cases, which suggests an increased metabolic activity in remaining motor neurons.</p><p>Motor neurons dying in ALS might go through apoptosis (programmed cell death), so immunohistochemical and TUNEL techniques were applied on thoracic spinal cord from ALS patients to evaluate the possibility of an apoptotic process. The increased Bax expression indicates an apoptotic process and further, motor neurons were TUNEL-positive, indicating DNA degradation caused by programmed cell death.</p><p>Muscle biopsies were obtained from ALS patients, and mRNA levels for the neurotrophic factors GDNF and BDNF were measured and compared to control subjects. GDNF levels were increased in muscle tissue in ALS whereas BDNF levels were unaltered.</p><p>Levels of GDNF and BDNF were also measured in cerebrospinal fluid from ALS patients and controls using ELISA methodology. Levels of BDNF were unaltered in ALS cornpared to controls. GDNF however was not detectable in controls whereas 12 out of 15 ALS patients had measurab1e levels of GDNW. A marked upregulation of endogenous GDNF and GDNF mRNA in ALS CSF and muscle respectively is of special interest in relation to clinical trials where GDNF is administered to this group of patients.</p>

Amyotrophic lateral sclerosis is a fatal, progressive neurodegenerative disease with unknown ethiology. The aim of this study was to increase understanding of the pathophysiological mechanisms of dying motor neurons and wasting muscle tissue in this particular disorder. Quantitative receptor autoradiographic methodology was applied on cervical spinal cord sections from patients with ALS to evaluate the specific binding of the acetylcholine transporter 3H-vesamicol in motor neurons. Despite a significant reduction of the number of ventral motor neurons in ALS, the 3H-vesamicol binding was not reduced in ALS compared to control cases, which suggests an increased metabolic activity in remaining motor neurons. Motor neurons dying in ALS might go through apoptosis (programmed cell death), so immunohistochemical and TUNEL techniques were applied on thoracic spinal cord from ALS patients to evaluate the possibility of an apoptotic process. The increased Bax expression indicates an apoptotic process and further, motor neurons were TUNEL-positive, indicating DNA degradation caused by programmed cell death. Muscle biopsies were obtained from ALS patients, and mRNA levels for the neurotrophic factors GDNF and BDNF were measured and compared to control subjects. GDNF levels were increased in muscle tissue in ALS whereas BDNF levels were unaltered. Levels of GDNF and BDNF were also measured in cerebrospinal fluid from ALS patients and controls using ELISA methodology. Levels of BDNF were unaltered in ALS cornpared to controls. GDNF however was not detectable in controls whereas 12 out of 15 ALS patients had measurab1e levels of GDNW. A marked upregulation of endogenous GDNF and GDNF mRNA in ALS CSF and muscle respectively is of special interest in relation to clinical trials where GDNF is administered to this group of patients.

Peripheral nerve trauma is a common cause of considerable functional morbidity, and healthcare expenditure. Particularly in the ~15% of injuries unsuitable for primary repair, standard clinical management results in inadequate sensory restitution in the majority of cases, despite the rigorous application of complex microsurgical techniques. This can largely be explained by the failure of surgical management to adequately address the neurobiological hurdles to optimal regeneration. Most significant of these is the extensive sensory neuronal death that follows injury, and which is accompanied by a reduction in the regenerative potential of axotomised neurons, and in the supportive capacity of the Schwann cell population if nerve repair is delayed. The present study aimed to accurately delineate the timecourse of neuronal death, in order to identify a therapeutic window during which clinically applicable neuroprotective strategies might be adopted. It then proceeded to investigate means to increase the regenerative capacity of chronically axotomised neurons, and to augment the Schwann cells’ ability to promote that regenerative effort. Unilateral sciatic nerve transection in the rat was the model used, initially assessing neuronal death within the L4&amp;5 dorsal root ganglia by a combination of morphology, TdT uptake nick-end labelling (TUNEL), and statistically unbiased estimation of neuronal loss using the stereological optical disector technique. Having identified 2 weeks, and 2 months post-axotomy as the most biologically relevant timepoints to study, the effect upon neuronal death of systemic treatment with acetyl-L-carnitine (ALCAR 10, or 50mg/kg/day) or N-acetyl-cysteine (NAC 30, or 150mg/kg/day) was determined. A model of secondary nerve repair was then adopted; either 2 or 4 months after unilateral sciatic nerve division, 1cm gap repairs were performed using either reversed isografts, or poly-3-hydroxybutyrate (PHB) conduits containing an alginate-fibronectin hydrogel. Six weeks later nerve regeneration and the Schwann cell population were quantified by digital image analysis of frozen section immunohistochemistry. Sensory neuronal death begins within 24 hours of injury, but takes 1 week to translate into significant neuronal loss. The rate of neuronal death peaks 2 weeks after injury, and neuronal loss is essentially complete by 2 months post-axotomy. Nerve repair is incompletely neuroprotective, but the earlier it is performed the greater the benefit. Two clinically safe pharmaceutical agents, ALCAR &amp; NAC, were found to virtually eliminate sensory neuronal death after peripheral nerve transection. ALCAR also enhanced nerve regeneration independently of its neuroprotective role. Plain PHB conduits were found to be technically simple to use, and supported some regeneration, but were not adequate in themselves. Leukaemia inhibitory factor enhanced nerve regeneration, though cultured autologous Schwann cells (SC’s) were somewhat more effective. Both were relatively more efficacious after a 4 month delay in nerve repair. The most profuse regeneration was found with recombinant glial growth factor (rhGGF-2) in repairs performed 2 months after axotomy, with results that were arguably better than were obtained with nerve grafts. A similar conclusion can be drawn from the result found using both rhGGF-2 and SC’s in PHB conduits 4 months after axotomy. In summary, these findings reinforce the significance of sensory neuronal death in peripheral nerve trauma, and the possibility of its` limitation by early nerve repair. Two agents for the adjuvant therapy of such injuries were identified, that can virtually eliminate neuronal death, and enhance regeneration. Elements in the creation of a bioartificial nerve conduit to replace, or surpass autologous nerve graft for secondary nerve repair are presented.

Gliomas are the most common primary tumors of the central nervous system believed to arise from glial cells. Invasive growth and inherent propensity for malignant progression make gliomas incurable despite extensive treatment. I have developed a life-like orthotopic glioma model and used this and other in vivo models to study basic mechanisms of glioma development and treatment. Previous studies had indicated that experimental gliomas could arise from glial stem cells and astrocytes. The present thesis describes the making and characterization of a novel mouse model, Ctv-a, where gliomas are induced from oligodendrocyte progenitor cells (OPCs). Our study shows that OPCs have the capacity to give rise to gliomas and suggests in light of previous data that the differentiation state of the cell of origin affects tumor malignancy. CDKN2A encodes p16INK4a and p14ARF (p19Arf in mouse) commonly inactivated in malignant glioma. Their roles in experimental glioma have been extensively studied and both proteins have tumor suppressor functions in glial stem cells and astrocytes. Here, we demonstrate that p19Arf only could suppress gliomagenesis in OPCs while p16Ink4a had no tumor suppressive effect. Functional DNA repair is pivotal for maintaining genome integrity, eliminating unsalvageable cells and inhibiting tumorigenesis. We have studied how RAD51, a central protein of homology-directed repair, affected experimental glioma development and have found that expression of RAD51 may protect against genomic instability and tumor development. Angiogenesis, the formation of new blood vessels from pre-existing ones, is a central feature of malignant progression in glioma. Antiangiogenic treatment by inhibition of vascular endothelial growth factor receptor signaling is used in the clinic for treatment of some cancers. We have investigated the effect of an alternative antiangiogenic protein, histidine-rich glycoprotein (HRG), on glioma development and found that HRG could inhibit the formation of malignant gliomas and completely prevent the formation of glioblastoma.

Thanks to pioneering scientists and clinicians, prosthetic devices that are controlled by intra-cortical electrodes recording one's 'thoughts' are a reality today, and no longer merely in the realm of science fiction. However, widespread clinical use of implanted electrodes is hampered by a lack of reliability in chronic recordings, independent of the type of electrodes used. The dominant hypothesis has been that astroglial scar electrically impedes the electrodes. However, recent studies suggest that the impedance changes associated with the astroglial scar are not high enough to interfere significantly impair neural recordings. Furthermore, there is a time delay between when scar electrically stabilizes and when neural recordings fail (typically >1 month lag), suggesting that scar, per se, does not cause chronic recording unreliability. In this study, an alternative hypothesis was tested in a rat model, namely, that chronic inflammation surrounding microelectrodes causes a local neurodegenerative state. Chronic inflammation was varied in three ways: 1) stab wound control, 2) age-matched control, and 3) inter-shank spacing of a multishank electrode. The results of this study suggest that chronic inflammation, as indicated by activated microglia and reactive astrocytes, is correlated with local neurodegeneration, marked by neuron cell death and dendritic loss. Surprisingly, axonal pathology in the form of hyperphosphorylation of the protein Tau (the hallmark of many tauopathies, including Alzheimer's Disease) was also observed in the immediate vicinity of microelectrodes implanted for 16 weeks. Additionally, work is presented on a fast, non-invasive method to monitor the astrocytic response to intra-cortical electrodes using electrical impedance spectroscopy. This work provides a non-invasive monitoring tool for inflammation, albeit an indirect one, and fills a gap which has slowed the development of strategies to control the inflammatory tissue response surrounding microelectrodes and thereby improve the reliability of chronic neural recordings. The results of these experiments have significance for the field of neuroengineering, because a more accurate understanding of why recordings fail is integral to engineering reliable solutions for integrating brain tissue with microelectrode arrays.

Mild traumatic brain injury (mTBI), often referred to as concussion, has become increasingly recognized as a serious health issue in the general population. The prevalence of mTBI in athletes, particularly repeated injuries in young athletes, is of great concern as injuries to the developing brain can have long-term detrimental effects. In this study we used a novel awake closed-head injury (ACHI) model in rodents to examine repeated mTBI (rmTBI), to determine if repeated injuries produced the neurological and molecular changes evident with human concussion. Animals were administered 4, 8, and 16 rmTBIs and acute neurological assessments were performed after the injuries. Changes in glial fibrillary acidic protein (GFAP) and ionized calcium-binding adapter molecule 1 (Iba-1) levels were assessed using Western blot analysis at one day following rmTBI in the ipsilateral dentate gyrus (DG) and the cornu ammonis (CA) regions of the hippocampus and the cortex (CX) indicative of astrocyte and microglial cell reactivity. Results indicated that the ACHI model produces neurological deficits immediately after the injuries, with the most deficits arising in the rmTBI16 group. Despite deficits in all injury groups, histological staining with cresyl violet revealed no significant morphological tissue damage to the brain. Western blot analysis, however, showed a significant increase in DG and CX GFAP expression in the rmTBI16 group with no changes in Iba-1 levels. This suggests an acute activation of astrocytes in response to injury, with a delay or absence of microglial activation. Our findings show that with repetitive concussions, we are able to detect acute neurological and molecular changes in the juvenile female brain. However, further investigation is necessary to determine if these are transient changes. / Graduate

Ratos Wistar machos adultos jovens (6 meses) e velhos (24-25 meses) foram alocados em treinamentos de endurance (corrida em esteira) ou resistido (escalada em grade) durante 6 semanas e comparados a controles sedentários (n=6). Ao final, músculos dos membros posteriores (sóleo e gastrocnêmio) foram analisados por histogramas e atividade total da enzima acetilcolinesterase (AChE). Na medula espinhal lombar, motoneurônios (MN) foram contados, bem como astrócitos da substância cinzenta marcados com GFAP. Densidades ópticas foram medidas nos cornos ventral (CV) e dorsal (CD) para CGRP-ir (MN e CD), AChE e 5-HT-ir (CV e CD). Para histogramas, dados foram analisados usando-se MANOVA e post hoc de Tukey. Os demais dados foram analisados usando-se ANOVA de 1 via e post hoc de Duncan. Resultados: histogramas de ratos jovens mostraram perfis de distribuição distintos após corrida (predominância de fibras de médio diâmetro) ou escalada (predominância de fibras de grande diâmetro) no músculo gastrocnêmio, mas não no sóleo. O perfil de predominância de fibras de pequeno diâmetro observado em ratos velhos sedentários foi igualmente revertido por corrida ou escalada, mas ratos velhos apresentaram limitado aumento de fibras de maior diâmetro. Tanto corrida quanto escalada diminuíram a atividade da AChE muscular. A medula espinhal de animais velhos apresentou menor número de MN e aumento do número de astrócitos. Tanto corrida quanto escalada reduziram a astrogliose no CV, mas não no CD. Ratos velhos mostraram aumento da CGRP-ir em MN, mas nenhum treinamento alterou a CGRP-ir em MN ou no CD. Tanto corrida quanto escalada aumentaram a AChE no CV em todos os grupos treinados. A escalada diminuiu AChE no CD e 5-HT-ir no CV. Nos ratos jovens, a corrida elevou 5-HT-ir no CD, mas não nos ratos velhos. Estes resultados sugerem que distintas modalidades de exercícios crônicos evocam diferentes respostas de neurotransmissores na medula espinhal em diferentes idades. / Young (6 months) and aged (24-25 months) male Wistar rats were assigned to endurance training (ET - treadmill running) and resistance training (RT - grid climbing with increasing weights) during 6 weeks and compared to sedentary controls (n=6). At the end, hindlimb muscles (soleus and gastrocnemius) were analysed by histograms and total AChE activity. In the lumbar spinal cord, motoneurons (MN) were counted, as well as gray matter's GFAP-labeled astrocytes. Optical densities were measured in the ventral (VH) and dorsal (DH) horns for CGRP-ir (MN and DH), AChE staining and 5-HT-ir (VH and DH). Data from histograms were analysed using MANOVA and Tukey’s post hoc. The remaining data Weir analysed using ANOVA and Duncan´s post hoc. Results: gastrocnemius, but not soleus, muscle histograms in young rats showed distinct fiber distribution profiles under ET (toward medium-diameter fibers) and RT (toward large-diameter fibers). The predominance in small-diameter muscle fibers in aged rats was similarly reversed by ET and RT, but aged rats presented limited increase in large-diameter muscle fibers. Both ET and RT decreased muscle AChE activity. The aged spinal cords presented MN loss and greater astrocyte numbers. Both ET and RT reduced astrogliosis in VH, but not in DH. The aged rats displayed elevated CGRP-ir in MN, and neither ET nor RT altered CGRP-ir in MN or DH. Exercise (ET and RT) markedly increased AChE staining in VH in all groups. RT decreased AChE in DH and 5-HT-ir in VH. In young rats, running elevated 5-HT-ir in the DH. These results suggest that different chronic exercise modalities and age evoke distinct spinal cord neurotransmitter responses.

A hipóxia-isquemia (HI) é a principal causa de mortalidade no período perinatal e, nos sobreviventes, a incidência de comorbidades neurológicas é elevada. O encéfalo imaturo, altamente susceptível ao insulto hipóxico-isquêmico, é bastante sensível a estímulos ambientais tais como o enriquecimento ambiental (EA). Os objetivos deste estudo foram: 1) investigar o desempenho comportamental em um novo teste de memória e aprendizagem, o Ox-maze; 2) analisar a atividade das enzimas Na+,K+-ATPase, catalase (CAT) e glutationaperoxidase (GPx) no hipocampo; 3) caracterizar os neurônios piramidais da região CA1 hipocampal quanto à arborização dendrítica; 4) analisar alterações astrocíticas e sinápticas pela avaliação da imunoreatividade das proteínas GFAP e sinaptofisina usando a técnica de imunofluorescência e, 5) quantificar a densidade celular por meio de cortes semifinos da região CA1 do hipocampo de animais hipóxico-isquêmicos expostos a um ambiente enriquecido. Ratos com sete dias de idade foram divididos em quatro grupos e submetidos ou não ao procedimento cirúrgico de acordo com o grupo experimental ao qual pertenciam: controle mantido em ambiente padrão (CTAP), controle em ambiente enriquecido (CTAE), HI em ambiente padrão (HIAP) e HI em ambiente enriquecido (HIAE). Passado o período de EA (1h/dia, 6 dias/semana, 9 semanas iniciando após o desmame), os parâmetros mencionados foram avaliados nos animais. Os dados indicaram que a HI causou um prejuízo na memória e no aprendizado no teste do “OX-maze”, o qual foi revertido pelo efeito do ambiente enriquecido. A HI causou diminuição da atividade enzimática da Na+,K+-ATPase no hipocampo contralateral, assim como uma redução na imunorreatividade à sinaptofisina e nadensidade neuronal, sendo que o EA foi efetivo na recuperação da atividade da enzima Na+,K+-ATPase e dos níveis de sinaptofisina no hipocampo contralateral à lesão. As atividades de CAT e GPX não foram alteradas pela HI em nenhum dos grupos avaliados, mesmo resultado encontrado nas análises de GFAP e de padrão de arborização dendrítica. Por fim, neste estudo foi observado o importante efeito lesivo causado pela HI neonatal e o papel do EA como estratégia neuroprotetora na recuperação funcional, na atividade da Na+,K+-ATPase e na expressão de sinaptofisina. Este estudo traz avanços em busca dos mecanismos pelos quais a melhora funcional ocorre em animais HI expostos ao EA, mas pode-se verificar que não fica totalmente esclarecido como esta estratégia atua. Outros estudos são necessários para a identificação de possíveis mecanismos que atuem como mediadores da resposta funcional do EA após um evento isquêmico. / Hypoxia-ischemia (HI) is the main mortality cause in perinatal period and, in survivors, the incidence of neurological disabilities is elevated. The immature brain, highly susceptible to hypoxic-ischemic insult, is sensible to environmental stimuli, as environmental enrichment (EE). The aims of this study were to investigate: 1) behavioral performance in a new memory and learning task, the oxmaze task; 2) evaluate Na+,K+-ATPase, catalase (CAT) and glutathione peroxidase (GPx) activities in the hippocampus; 3) characterizes dendritic arbor in pyramidal neurons from CA1 region from hippocampus; 4) analyze alterations in hippocampal synaptophysin and GFAP immmunoreactivity and, 5) analyze neuronal density alterations in hippocampus of hypoxic-ischemic rats exposed to enriched environment. Seven-day-old rats were divided into four groups: controlmaintained in standard environment (CTSE), control submitted to EE (CTEE), HI in standard environment (HISE) and HI in EE (HIEE). Past the end of EE period (1 hour/day, 6 days/week, 9 weeks), mentioned parameters were evaluated in animals. Present results indicate learning and memory in the “OXmaze” task were impaired in HI rats and this effect was recovered after EE. On the contralateral hemisphere, HI caused a decrease in Na+,K+-ATPase activity that was recovered by EE. Results also indicate that HI damage decreases hippocampal synaptophysin immunoreactivity and neuronal density, moreover EE was effective in recovering synaptophysin levels on contralateral to the lesion hippocampus. The activities of GPx and CAT were not changed by HI in any group evaluated, some result founded on GFAP immunoreactivity and dendritic arborization characterization analysis. In conclusion, the important effect of HI lesion and the role of EE like neuroprotective strategy on functional impairment and on Na+,K+-ATPase activity and synaptophysin immunoreactivity was proven. Although this study have important advances in search of mechanisms by which the functional enhancement occurs in the animals submitted to HI and exposed to EE, it can be seen that it is not completely clear how this approach works. Further studies are needed to identify possible mechanisms that act as mediators of EE functional response after an ischemic event.