Olfactory receptor neurons (ORNs) maintain the ability to regenerate. These neurons reside in the olfactory epithelium and project axons that connect to the olfactory bulbs. Despite the diffuse distribution of ORNs in the olfactory epithelium, they converge at discrete glomeruli in the olfactory bulb. In the P2 IRES tau-lacZ mouse, the P2 ORN subtype has been previously mapped to two glomeruli, using X-gal staining. To determine if age affects ORN regeneration, left olfactory nerve transections were performed on P2 mice from immature (five-weeks old) and mature (1 6-weeks old) groups. Following recovery, the olfactory bulbs were processed to observe ORN regeneration. A significant difference was seen in the number and mapping of full P2 glomeruli between lesioned and control olfactory bulbs, but not between the age groups. This suggests that age differences between the two groups in this study were not large enough to affect the regeneration of P2 ORNs.

Tactile stimulation, an important physiological component of the sexual experience, has the ability to influence the body’s representation in the brain. The sensory homunculus proposed by Penfield and Rasmussen illustrates the way in which the body is represented within the somatosensory cortex. Due to neuroplasticity, this map has the ability to adapt to differing levels of tactile input. How sexual arousal affects, or is represented by, the sensory homunculus is unknown. The study sought to identify: which body areas, rated by participants, are high in their ability to facilitate sexual arousal; to measure the intensity of the different body areas; and to identify whether the areas of greatest intensity lie adjacent cortically to the genital area thus supporting the hypothesised neuroplasticity of brain functioning. The current study was conducted through an online survey which was completed by volunteers with access to university portal sites, social networking sites and referrals. Sampling was convenient and comprised 208 heterosexual males. Data were treated quantitatively through descriptive (frequencies) and inferential (correlations, rotated factor analysis) statistics. The research findings provide support for the sensory homunculus mapping and suggest that there are three areas (genital, facial and trunk) that facilitate sexual arousal. The ability to facilitate sexual arousal is proposed to lie in the close proximity that these areas have within the three erogenous centres (cortically) as well as co-activation of body areas through perceived erogeneity and physiological proximity. This has important implications for sex therapy for individuals in which feeling in the genital area is lacking.

Várias evidências têm caracterizado os efeitos benéficos do gangliosídeo GM1 no tratamento de lesões neurológicas. O GM1 também foi estudado para o tratamento de doenças neurodegenerativas, principalmente em relação ao seu papel na neuroplasticidade e neuroproteção. O objetivo deste estudo foi analisar os possíveis efeitos de GM1 em modelo de doença de Parkinson induzida pela injeção intraestriatal unilateral de 6-hidroxidopamina (6-OHDA) em ratos. O GM1 foi injetado em conjunto com 6-OHDA e sete dias após a cirurgia os cérebros foram coletados para análise. Os resultados bioquímicos mostraram que o tratamento com GM1 intraestrial atenua aspectos inflamatórios e reduz os indicadores de morte neuronal, tal como evidenciado pela manutenção dos níveis de GFAP, OX-42 e caspase-3 em níveis de controle. A melhoria no tratamento por GM1 foi também demonstrada com a preservação de um fator neurotrófico derivado do encéfalo (BDNF) e os níveis de tirosina hidroxilase após 6-OHDA. A análise comportamental corrobora os achados bioquímicos, demonstrando que o GM1 possui a capacidade de preservação dos movimentos, visto pelo teste de cilindro. Sugerimos que o GM1 exerce neuroproteção no modelo de 6-OHDA, quando administrado por uma via local. Isto poderia representar um meio viável para transpor as barreiras farmacocinéticos que afetam a entrega de uma concentração apropriada da droga para áreas do cérebro / Several evidences have characterized the beneficial effects of ganglioside GM1 in the treatment of neurological lesions. GM1 has also been studied for the treatment of neurodegenerative diseases, mainly in relation to its role in neuroplasticity and neuroprotection. The objective of this study was to analyze the possible effects of GM1 on a model of Parkinson\'s disease induced by unilateral intra-striatal injection of 6-hydroxydopamine (6-OHDA) in rats. The GM1 was injected together with 6-OHDA and seven days after surgery the brains were collected for analysis. Biochemical results showed that treatment with intra-striatal GM1 attenuates inflammatory aspects and reduces the indicators of neuronal death, as evidenced by maintaining levels of GFAP, OX-42 and caspase-3 at control levels. Improvement after GM1 treatment was also demonstrated by the preservation of a brain-derived neurotrophic factor (BDNF) and tyrosine hydroxylase levels after 6-OHDA. The behavioral analysis corroborates the biochemical findings, demonstrating that GM1 has the ability to preserve movements, as seen by the cylinder test. We suggest that GM1 exerts neuroprotection in the 6-OHDA model when administered by a local route. This could represent a viable means of overcoming the pharmacokinetic barriers affecting the delivery of an appropriate concentration of the drug to areas of the brain

Antidepressivos clássicos apresentam uma série de limitações na prática clínica, sendo uma das mais relevantes a latência de 4 a 8 semanas para indução de uma melhora significativa dos sintomas. Existem evidências que canabinóides, como o fitocanabinóide canabidiol (CBD) e o inibidor de degradação da anandamida URB597 (URB) geram efeitos comportamentais semelhantes aos antidepressivos. Canabinóides e antidepressivos podem, inclusive, apresentar mecanismos moleculares em comum. O presente estudo investigou os efeitos comportamentais e neuroplásticos de uma semana de tratamento com a combinação de uma dose do antidepressivo escitalopram (ESC) que gera efeitos comportamentais após 3 semanas de tratamento com doses sub-efetivas de canabinóides em camundongos estressados. Para isso, camundongos C57Bl6 machos foram submetidos ao protocolo de estresse crônico imprevisível (CUS) ou ao protocolo de estresse de derrota social (SDS) por 10 dias. Os animais foram divididos em 7 grupos experimentais (n=8-13; Controle (Não estressado); Veículo (Veí/Veí); ESC 10mg/kg (Esc/Veí); CBD 7,5 mg/kg (Veí/CBD); URB 0,1 mg/kg (Veí/CBD); ESC/CBD; ESC/URB) e foram tratados durante os 7 últimos dias do protocolo de estresse (via i.p.). O tratamento com a combinação de escitalopram e CBD gerou respostas preditivas de um efeito do tipo-antidepressivo no teste de suspensão pela cauda e de um efeito do tipo-ansiolítico no novelty suppressed feeding tanto no modelo de estresse homotípico (SDS) quanto no modelo de estresse heterotípico (CUS). Paralelamente às alterações comportamentais, foi observado que o grupo ESC/CBD apresentou uma maior expressão relativa de sinaptofisina no córtex pré-frontal, evidenciando um possível efeito pró-sinaptogênico da combinação. Esse mesmo tratamento promoveu aumento na expressão de sinaptotagmina e ?-actina no hipocampo. Os resultados encontrados no presente estudo evidenciam que a combinação com CBD pode otimizar a ação do antidepressivo escitalopram. / Despite their widespread use, antidepressant drugs show some limitations in the clinical practice, including a delayed onset of action. Cannabinoid drugs, such as canabidiol (CBD) and the anandamide degradation inhibitor URB597 (URB), have shown behavioral effects that are similar to those induced by antidepressants in preclinical studies. Antidepressants and cannabinoids might even share common mechanisms. This study aimed to evaluate the behavioral and neuroplastic effects of one week of treatment of stressed animals with the combination of sub-effective doses of cannabinoids with 10mg/Kg of escitalopram (ESC)- dose that prevented- stressinduced behavioural changes only after 3 weeks of treatment. Male C57Bl6 mice were subjected to a 10-day protocol of either social defeat stress (SDS) or chronic unpredictable stress (CUS). Animals were divided in 7 experimental groups (n=8-13; Control (Non-stressed); Vehicle (Veh/Veh); ESC 10mg/kg (Esc/Veh); CBD 7,5mg/kg (Veh/CBD); URB 0,1mg/kg (Veh/CBD); ESC/CBD; ESC/URB) and the treatment was conducted during the 7 last days of the stress protocol (via i.p.). The treatment with the combination of ESC and CBD produced responses that are considered predictive of antidepressant-like effects in the tail suspension test and of anxiolytic-like effects in the novelty suppressed feeding in both the homotypic stress (SDS) and the heterotypic stress (CUS) models. In paralel with the bevavioral outcomes, molecular analysis revealed that the ESC/CBD group showed a higher relative expression of synaptophysin in the PFC, suggesting a pro-synaptogenic effect of the combination. Increased relative expression of synaptotagmin and ?-actin in the hippocampus following ESC/CBD treatment were also reported. The results presented in this study provide evidence that the combination with CBD can optimize the action of the antidepressant escitalopram.

A lesão medular é uma injúria do sistema nervoso central que resulta em grande déficit funcional. É uma condição relacionada ao desenvolvimento industrial e tecnológico e acomete principalmente adultos jovens em idade produtiva. Apesar de algumas tentativas terapêuticas estarem sob investigação, ainda não há tratamento eficaz que garanta recuperação funcional. A maioria das estratégias utilizadas visa estimular eventos de neuroplasticidade. A cúrcuma é um composto dietético que tem potencial terapêutico por interferir em processos inflamatórios, oxidativos e imunológicos. O presente estudo investigou possíveis efeitos terapêuticos da cúrcuma após hemissecção medular em ratos. O protocolo experimental foi aprovado pelo Comitê de Ética em Uso de Animais da Escola de Artes, Ciências e Humanidades. Os animais foram submetidos à hemissecção medular após a medula espinhal ser exposta por laminectomia. Os animais foram divididos em 2 grupos experimentais: i) lesionado com cúrcuma (LC); ii) lesionado sem tratamento (LS). Os testes comportamentais BBB Score, Combined Behavior Score, plano inclinado e Beam Walking foram realizados 24h, 72h e 7 dias depois da lesão para avaliar o reaprendizado medular e a recuperação funcional. Os resultados demonstraram melhora do comportamento sensitivo-motor dos animais, provavelmente envolvendo neuroproteção das vias de tato, dor e pressão. As propriedades anti-inflamatórias e antioxidantes da cúrcuma podem ter levado à melhora funcional. Análises celulares e moleculares são necessárias para entendermos melhor os efeitos no epicentro da lesão depois do tratamento com a cúrcuma. Um dos possíveis efeitos prováveis é sobre a conversão de alguns ácidos graxos envolvidos na inflamação, como o ácido araquidônico, diminuindo sua ação e gerando ganhos funcionais. O uso da cúrcuma na fase aguda da hemissecção medular interferiu positivamente na recuperação sensitivo-motora deflagrando, portanto, eventos de neuroproteção e neuroplasticidade / The spinal cord injury is a condition that results in severe functional deficit. It is related to the industrial and technological development and affects mainly young adults. Despite some therapeutic trials are under investigation, there is no treatment that guarantees functional recovery. Most of those strategies for recovery involve neuroplasticity. Curcumin is a dietetic compound with known therapeutic potential, interfering on inflammatory, oxidative and immunological processes. The present study investigated the effects of the treatment with curcumin on acute phase of spinal cord hemi-section in rats. The protocol has been approved by Ethics Committee of School of Arts, Sciences and Humanities. The animals were submitted to hemi-section after laminectomy and were divided in two groups: i) injured with curcumin (LC); ii) injured without treatment (LS). The following behavioral tests were performed 24h, 72h and 7 days after lesion: BBB Score, Combined Behavior Score, inclined plane and Beam Walking test aiming to evaluate medular relearning and functional recovery. The tests indicated an improvement of the sensitive-motor behavior probably by neuroprotection of tactile, pain and pressure pathways. The anti antiinflammatory and antioxidant properties of curcumin could result in functional improvement. Cellular and molecular analysis are necessary to better understand the effects could be over the conversion of some fatty acids involved on inflammation, such as arachidonic acid, reducing its action and promoting functional gain. The use of curcumin in the acute phase of spinal cord hemi-section seems to interfere positively in sensorial-motor recovery triggering neuroprotection and plasticity

A dor crônica disseminada é o principal sintoma da fibromialgia. Com a ausência de tratamento específico, uma alternativa emergente para o tratamento de pacientes refratários é a estimulação do córtex motor (ECM), através de técnicas não-invasivas. Os mecanismos analgésicos de ECM são pouco conhecidos, estando provavelmente vinculados à neuroplasticidade na matriz da dor. Um modelo de fibromialgia foi induzido em ratos pela administração de reserpina (2 mg/kg por 3 dias consecutivos) e avaliada a sensibilidade mecânica. A ECM (1V, 210μs e 60Hz, 15 minutos por sessão) restaurou a sensibilidade mecânica no modelo de fibromialgia, com uma ou 5 sessões. No corno posterior da medula espinal, a ECM restaurou os níveis de BDNF diminuídos pelo modelo de fibromialgia, e diminuiu a fosforilação de TrkB. Na PAG, ECM aumentou GDNF, mas diminuiu GFAP e a fosforilação de AKT e ERK-1/2. No ACC, a ECM diminuiu a fosforilação de AKT, aumentou BDNF e manteve níveis normais de GFAP no modelo. Assim, o efeito antinociceptivo da ECM está associada a diversas alterações neuroplásticas. / Chronic widespread pain is the main symptom of fibromyalgia. Without specific treatment, an emerging alternative for the treatment of refractory patients is the motor cortex stimulation (MCS) through non-invasive techniques. The analgesic mechanisms of MCS are poorly understood, being linked to neuroplasticity in the pain matrix. A fibromyalgia model was induced in rats by administration of reserpine (2 mg/kg for 3 consecutive days) and mechanical sensitivity was assessed. The ECM (1V, 210μs and 60Hz, 15 minutes per session) restored the mechanical sensitivity in the fibromyalgia model, with one or 5 sessions. In the posterior horn of the spinal cord, ECM restored the BDNF levels decreased in the fibromyalgia model, and decreased the phosphorylation of TrkB. In the PAG, ECM increased GDNF but decreased GFAP and phosphorylation of AKT and ERK-1/2. In ACC, ECM decreased AKT phosphorylation, increased BDNF, and maintained normal GFAP levels in the model. Thus, the antinociceptive effect of ECM is associated with several neuroplastic alterations.

Apart from CFRD, low cognitive skill index (CSI) was also found in CF patients and was attributed the lacking of vitamin E. Since it is known that insulin plays a role in the learning and memory, decreased plasma insulin level in CF patients is an alternative mechanism for impaired cognitive function. Although numerous studies have found that insulin can improve learning and memory, the mechanism of it is not well understood. In this study, we investigated the effect of insulin on the expression of hippocampal early-phase long-term potentiation (E-LTP) in the immature rats. Hippocampal brain slices were acutely prepared from 10-12 days and 2 months old rats and field excitatory postsynaptic potentials (tEPSCs) were recorded from CA1 region by a multi-electrode in vitro recording system. In the control group, the hippocampal slices of neonatal rats showed no increase in the magnitude of fEPSC after conventional high frequency stimulation (HFS). After pretreatment of the slices with 0.08ng/ml insulin for over one hour, there was no significant change in the magnitude of E-LTP. However, when the insulin concentration increased to 0.8ng/ml, a significant increase in the magnitude of E-LTP was observed. On the contrary, any doses of insulin failed to affect the magnitude of E-LTP of mature rats. These results suggested that insulin could dose-dependently facilitate the production of E-LTP in the hippocampus of infant rats. Application of AG-1024, an inhibitor of insulin receptor, largely abolished the insulin-dependent E-LTP in immature rats rather than adult rats, indicating the involvement of insulin signaling pathway in the insulin effect. On the other hand, increasing the concentration of glucose from 11mM to 22 or 33 mM did not facilitate the E-LTP and application of indinavir, a blocker of insulin-sensitive glucose transporter-4, did not inhibit the effect of insulin. Therefore, it is unlikely that the facilitory action of insulin on E-LTP is via an indirect effect on glucose homeostasis or utilization. Pretreatment with the MAPK pathway inhibitor PD98059 blocked insulin-mediated E-LTP facilitation. Furthermore, the tetanic stimulation induced a significant increase in the level of phosphorylated p42MAPK in the insulin-treated hippocampus than that in the control group. In conclusion, our results suggested that insulin could facilitate the production of hippocampal E-LTP in infant rats, which may play an important role in modulating the expression of LTP in the developing brain and perhaps is an underlying mechanism for the improving effect of insulin on learning and memory. Since insulin plays an important role in the developing brain, perhaps the deficiency of insulin effect resulted from CF patients induces the impairment of cognitive function. / Cystic fibrosis (CF), which is caused by the deficiency of cystic fibrosis transmembrne conductance regulator (CFTR), is the most common autosomal recessive systemic disease with an incidence of 1: 2500 in Caucasians. Cystic fibrosis-related diabetes (CFRD), as one of the complications of CF patients, is regarded as one of the leading co-morbidity in CF patients. The mechanism ofCFRD is attributed to the reduced number of islets due to pancreatic fibrosis caused by the loss of CFTR in pancreatic duct. However, the above mechanism failed to explain the dynamics of insulin secretion induced by glucose tolerance test (GTT) in some CF patients and therefore, we were forced to re-consider the mechanism for the pathogenesis of CFRD. Interestingly, the following facts imply that perhaps there is another mechanism for the onset of CFRD: decreased insulin secretion and decreased plasma HCO3 - concentration was observed in the metabolic acidosis disease, plasma HCO3- level increased accompanied by the elevation of plasma insulin after food intake and CFTR accounted for HCO3 - transport in many epithelial cells. These facts promoted us to hypothesize that the loss of HCO3--induced insulin secretion resulting from the deficiency of CFTR is an alternative mechanism for the onset of CFRD. Our results showed that HCO3- could induce insulin secretion of isolated islets from rats. Ca2+ imaging revealed that HCO3- dose-dependently induced an increase in intracellular Ca2+ ([Ca2+] i) in RIN-5F cells, an insulin-secreting cell line. Removal of extracellular Ca2+ or addition of nifedipine, the blocker of L-type Ca 2+ channel, decreased the effect of HCO3- significantly, indicating the activation of L-type Ca2+ channel during HCO3- stimulation. The inhibitory effect of BaCl2 implied the involvement of K+ channel. The results that HCO3--induced increase in [Ca 2+]i was reduced by PKA inhibitor and sAC blocker demonstrated that the pathway of sAC-cAMP-PKA-ATP-sentitive K+ channel (K ATP channel) was responsible for the effect of HCO3 -. The reduction of extracellular Cl- or the inhibitor of anion exchanger (AE) inhibited the [Ca2+]i increase induced by HCO3- significantly but the omission of external Na+ failed. The facts that CFTR blocker decreased the effect of HCO3- markedly and the expression of CFTR in RIN-5F cells revealed by western blotting suggested the CFTR-mediated HCO3- transport. These results suggested that HCO 3- could induce insulin secretion in a CFTR-dependent manner, which provided a new insight into the understanding of pathogenesis of CFRD and paved the way for the therapy of CFRD. / Zhao, Wenchao. / "November 2010." / Advisers: Chang Chan; Wing Ho Yung. / Source: Dissertation Abstracts International, Volume: 73-04, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 115-138). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Intervenções ambientais, como a exposição precoce a estressores ou a dietas ricas em calorias, podem alterar a trajetória da maturação neural e influenciar na susceptibilidade a certas patologias a longo-prazo. Neste contexto, o objetivo do presente estudo foi investigar os efeitos de uma exposição ao isolamento social durante o período pré-pubere associado ou não ao consumo precoce e crônico de uma dieta hiperlipídica (HFD) sobre aspectos cognitivos e emocionais, e possíveis mecanismos neuroquímicos associados a essas alterações, no hipocampo, no córtex pré-frontal e no núcleo accumbens de ratos machos na idade adulta. Os resultados mostraram que os dois fatores, estresse e dieta (separadamente), induziram um comportamento do tipo depressivo nos animais na idade adulta. Além disso, os animais isolados apresentaram um déficit cognitivo associado à memória de curta-duração e de trabalho, enquanto que animais com acesso à HFD demonstraram prejuízo somente na memória de curta-duração. Curiosamente, a interação entre os fatores (estresse e dieta) causou uma reversão dos déficits na memória de curta-duração. Em relação às avaliações do comportamento alimentar hedônico, observamos que o grupo com consumo crônico de HFD apresentou uma menor motivação para obter diferentes tipos de alimentos palatáveis doces. Essa redução motivacional não parece ser associada a uma menor palatabilidade e/ou a uma maior saciedade induzida pela HFD. Em relação aos marcadores de plasticidade analisados no córtex pré-frontal, observamos interações entre os fatores estresse e dieta na atividade da enzima Na+K+-ATPase, nos níveis de BNDF e no imunoconteúdo das proteínas AKT e MAPK/ERK, sendo que os fatores quando aplicados isolados diminuem os níveis dos parâmetros analisados, porém quando associados, os níveis retornam ou aumentam em relação aos valores do grupo controle. O hipocampo foi a estrutura mais afetada pelas intervenções ambientais neste trabalho. Observamos que tanto o estresse, como a dieta hiperlipídica (separadamente) causaram uma redução da plasticidade sináptica hipocampal, por meio de diferentes mecanismos: o acesso crônico à HFD afeta proteínas relacionadas ao funcionamento das sinapses, enquanto o isolamento social parece afetar mais particularmente a via de sinalização do BDNF. Com relação aos achados neuroquímicos no núcleo accumbens, observamos uma redução dos receptores dopaminérgico-1 (D1) e canabinóide-1 (CB1) com o consumo de HFD, enquanto que os animais isolados na pré-puberdade apresentaram uma redução do metabolismo dopaminérgico nesta estrutura. Em suma, esta tese demonstra que tanto o isolamento social e como o consumo contínuo de HFD causam comportamento do tipo depressivo e outras alterações comportamentais, e reduzem marcadores de plasticidade importantes no córtex prefrontal e hipocampo. O acesso à HFD também causa uma menor motivação para o comportamento alimentar hedônico. Assim, tais eventos precoces podem afetar a plasticidade neural levando a importantes alterações comportamentais, e assim predispor a diferentes patologias durante a vida. / Environmental interventions, such as early exposure to stressors or high calorie-diets, can alter the trajectory of neural maturation and influence the susceptibility to some pathologies throughout life. In this context, the aim of the present study was to investigate the effects of exposure to social isolation, during the pre-pubertal period, associated or not with early and chronic consumption of a hyperlipid diet (HFD) on cognitive and emotional aspects, and possible mechanisms associated with these changes, in the hippocampus, the prefrontal cortex and the nucleus accumbens of male rats in adulthood. The results showed that both pre-pubertal social isolation and chronic access to a hyperlipidic diet induced a depressive-like behavior in animals during adulthood. In addition, isolated animals had a cognitive deficit associated with short-term and working memory, whereas animals with access to HFD demonstrated impairment only in short-term memory. Interestingly, the interaction between the factors (stress and diet) caused a reversal in relation to short-term memory, remaining similar to the control group. Regarding the evaluations of the hedonic eating behavior, we observed that HFD group presented a lower motivation to obtain different sweet palatable foods. This impaired motivation does not appear to be associated with less palatability and/or satiety induced by the high-fat diet. Concerning plasticity markers in the prefrontal cortex, we observed interactions between stress and diet on Na+ K+-ATPase activity, BNDF levels and AKT and MAPK/ERK immunocontents. These interactions follow a similar profile: when applied alone, the levels of the analyzed parameters decrease, but when associated, the levels return or increase in relation to the values of the control group. The hippocampus was the structure most affected by the environmental interventions. Both stress and HFD caused a reduction of hippocampal synaptic plasticity through different mechanisms: chronic access to HFD affects proteins related to synaptic function, while social isolation affects the BDNF signaling pathway more significantly. Regarding the neurochemical findings in the nucleus accumbens, we observed a reduction in dopaminergic-1 (D1) and cannabinoid-1 (CB1) receptors with chronic HFD intake, whereas isolated animals had a reduction of dopaminergic metabolism in this same structure. In summary, this thesis shows that both social isolation and chronic consumption of HFD lead to depressive-like behavior and to other behavioral changes; they reduce plasticity markers in prefrontal cortex and hippocampus. HFD access also induced a lower motivation for hedonic feeding. Therefore, these early interventions may affect neural plasticity, leading to important behavioral changes, and thus, predispose to different pathologies later in life.

Adult hippocampal neurogenesis—a unique form of plasticity in the dentate gyrus (DG)—is regulated by experience, and when manipulated can have specific effects on behavior. Different methods have been used over the years to study new neurons’ functional role in the hippocampus, many of which focus on ablating neurogenesis. While ablation methods can test the necessity of adult-born granule cells (abGCs) for behavior, these techniques remove all abGCs from the circuit and thus do not allow one to determine which properties of abGCs are required for behavior. Such information is required to understand the mechanism of their action. Thus, new strategies are needed to determine what properties of young abGCs allow them to distinguish themselves from their mature counterparts and uniquely impact behavior. Recent hypotheses have suggested that the enhanced synaptic plasticity exhibited by 4–6-week-old abGCs allows them to uniquely contribute to hippocampal circuit function, and thus behavior. The primary goal of this thesis was to explore the contribution young abGCs’ heightened synaptic plasticity makes to hippocampal function. This was achieved using a transgenic mouse approach that allowed for the conditional deletion of NR2B from abGCs. Overall, iNR2BNes mice generated the same number of new neurons in adulthood as control mice at baseline. These neurons survived and matured with only a slight reduction in dendritic complexity. However, a potentially important electrophysiological property of these neurons—their enhanced synaptic plasticity—had been eliminated. From an electrophysiological standpoint, iNR2BNes mice resemble mice with ablated neurogenesis, while from all other neurogenic standpoints examined they most closely resemble wild-type mice. Consequently, these mice provided a novel model to test the extent to which young abGCs’ enhanced plasticity contributes to hippocampal-dependent behaviors. The results reveal that eliminating NR2B-containing NMDA receptors from abGCs does not alter baseline anxiety or antidepressant (AD)-like behavior. However, iNR2BNes mice differed from controls in measures of cognitive function. These mice were able to learn in the contextual fear conditioning test, but were impaired in the more difficult contextual fear discrimination test. Mice also exhibited a decreased novelty exploration phenotype that impaired their performance in the novel object recognition test. Together, these results indicate that the NR2B-dependent heightened plasticity exhibited by 4–6-week-old abGCs is necessary for responses to novelty and fine contextual discrimination, but does not contribute to baseline anxiety or emotionality. AD treatment increases levels of adult neurogenesis in the hippocampus, and these newborn neurons have been shown to be necessary for some of the behavioral effects of ADs seen in rodents. In addition, the maturation timeline of adult neurogenesis correlates with the onset of behavioral responses to ADs. ADs also enhance a neurogenesis-dependent form of long-term potentiation (LTP) in the DG evoked by medial perforant path stimulation under intact GABAergic tone called ACSF-LTP. Thus, a potential mechanism by which abGCs may contribute to AD behavioral efficacy is by providing extra plastic units to the DG circuit. This theory was tested by once again using the mouse line in which NR2B can be conditionally deleted from abGCs in the DG. Here, we found that deletion of the NR2B subunit significantly attenuated a neurogenesis-dependent behavioral response to fluoxetine in the novelty suppressed feeding test, and additionally blocked fluoxetine’s ability to enhance young abGCs’ maturation and subsequent integration into the hippocampal network. This suggests that eliminating abGCs’ enhanced plasticity decreases their ability to influence DG output resulting in an AD response that is less robust than seen in control mice. Control experiments revealed the specificity of this effect, as NR2B deletion did not impact the effect of fluoxetine in a neurogenesis-independent behavioral assay (tail suspension test) or in an assay that was insensitive to fluoxetine in this strain of mice (elevated plus maze). Our efforts to isolate the contribution of abGCs’ unique physiology from the neurogenic effects of fluoxetine were not entirely successful as the results presented here also revealed slight group differences in neurogenesis between control mice and mice lacking NR2B in young neurons. Yet, this data still supports the idea that fluoxetine increases the ability of abGCs to participate in DG output by increasing the chance that new neurons will be activated during DG stimulation. This may be achieved either by increasing their overall number, increasing their potential to make synaptic connections, or increasing their ability to strengthen their connections. However, due to the close link between activity and maturation that appears to be enhanced with fluoxetine treatment, a different approach with greater temporal resolution is needed to separate the neurogenic effects of fluoxetine from the physiological contribution abGCs make to hippocampal output. With this in mind, a mouse line in which abGCs could be temporally inhibited was also generated. Cellular and behavioral characterization of mice conditionally expressing hM4Di—a mutated muscarinic acetylcholine receptor that is insensitive to endogenous acetylcholine, but can be activated by the biologically inert, highly bioavailable compound, clozapine N-oxide (CNO)—has begun. Results show that acute CNO treatment in mice expressing this designer receptor exclusively activated by a designer drug (DREADD) in DG granule cells can impair encoding of contextual fear memory. Chronically treating these mice had an anxiogenic effect in the open field test, but otherwise anxiety and emotionality in these mice were comparable to controls. Chronic CNO treatment in mice expressing hM4Di in young abGCs effectively decreased these cells’ dendritic complexity, but did not alter proliferation or early survival. Thus, hM4Di DREADDs represent a novel tool that can be used to modulate activity of neurons in a temporally restricted manner, allowing for both acute and chronic manipulations of hippocampal granule cells. The experiments put forth in this thesis will highlight the importance of abGCs enhanced plasticity. The utility as well as potential pitfalls of the mouse models used here to test theories of abGC function will also be explored. Hopefully this analysis will provide an improved framework in which future experiments can be developed with the aim of uncovering novel insights into the hippocampal circuitry that underlies learning and memory and discovering new strategies for the treatment of neurological and psychiatric disorders.

Antidepressivos clássicos apresentam uma série de limitações na prática clínica, sendo uma das mais relevantes a latência de 4 a 8 semanas para indução de uma melhora significativa dos sintomas. Existem evidências que canabinóides, como o fitocanabinóide canabidiol (CBD) e o inibidor de degradação da anandamida URB597 (URB) geram efeitos comportamentais semelhantes aos antidepressivos. Canabinóides e antidepressivos podem, inclusive, apresentar mecanismos moleculares em comum. O presente estudo investigou os efeitos comportamentais e neuroplásticos de uma semana de tratamento com a combinação de uma dose do antidepressivo escitalopram (ESC) que gera efeitos comportamentais após 3 semanas de tratamento com doses sub-efetivas de canabinóides em camundongos estressados. Para isso, camundongos C57Bl6 machos foram submetidos ao protocolo de estresse crônico imprevisível (CUS) ou ao protocolo de estresse de derrota social (SDS) por 10 dias. Os animais foram divididos em 7 grupos experimentais (n=8-13; Controle (Não estressado); Veículo (Veí/Veí); ESC 10mg/kg (Esc/Veí); CBD 7,5 mg/kg (Veí/CBD); URB 0,1 mg/kg (Veí/CBD); ESC/CBD; ESC/URB) e foram tratados durante os 7 últimos dias do protocolo de estresse (via i.p.). O tratamento com a combinação de escitalopram e CBD gerou respostas preditivas de um efeito do tipo-antidepressivo no teste de suspensão pela cauda e de um efeito do tipo-ansiolítico no novelty suppressed feeding tanto no modelo de estresse homotípico (SDS) quanto no modelo de estresse heterotípico (CUS). Paralelamente às alterações comportamentais, foi observado que o grupo ESC/CBD apresentou uma maior expressão relativa de sinaptofisina no córtex pré-frontal, evidenciando um possível efeito pró-sinaptogênico da combinação. Esse mesmo tratamento promoveu aumento na expressão de sinaptotagmina e ?-actina no hipocampo. Os resultados encontrados no presente estudo evidenciam que a combinação com CBD pode otimizar a ação do antidepressivo escitalopram. / Despite their widespread use, antidepressant drugs show some limitations in the clinical practice, including a delayed onset of action. Cannabinoid drugs, such as canabidiol (CBD) and the anandamide degradation inhibitor URB597 (URB), have shown behavioral effects that are similar to those induced by antidepressants in preclinical studies. Antidepressants and cannabinoids might even share common mechanisms. This study aimed to evaluate the behavioral and neuroplastic effects of one week of treatment of stressed animals with the combination of sub-effective doses of cannabinoids with 10mg/Kg of escitalopram (ESC)- dose that prevented- stressinduced behavioural changes only after 3 weeks of treatment. Male C57Bl6 mice were subjected to a 10-day protocol of either social defeat stress (SDS) or chronic unpredictable stress (CUS). Animals were divided in 7 experimental groups (n=8-13; Control (Non-stressed); Vehicle (Veh/Veh); ESC 10mg/kg (Esc/Veh); CBD 7,5mg/kg (Veh/CBD); URB 0,1mg/kg (Veh/CBD); ESC/CBD; ESC/URB) and the treatment was conducted during the 7 last days of the stress protocol (via i.p.). The treatment with the combination of ESC and CBD produced responses that are considered predictive of antidepressant-like effects in the tail suspension test and of anxiolytic-like effects in the novelty suppressed feeding in both the homotypic stress (SDS) and the heterotypic stress (CUS) models. In paralel with the bevavioral outcomes, molecular analysis revealed that the ESC/CBD group showed a higher relative expression of synaptophysin in the PFC, suggesting a pro-synaptogenic effect of the combination. Increased relative expression of synaptotagmin and ?-actin in the hippocampus following ESC/CBD treatment were also reported. The results presented in this study provide evidence that the combination with CBD can optimize the action of the antidepressant escitalopram.