The objective of the present study was to examine the effects of prenatal exposure to alcohol on sensorimotor coordination, emotionality, learning and memory in young adult Wistar rats. Most of the recent reports concerning behavioral effects of fetal alcohol exposure refer to the juvenile period of life and very few studies investigated different aspects of behavior simultaneously in the same subjects. In the current study, alcohol was delivered to the pregnant dams by intragastric infusions, throughout gestation days (GD) 7-20, at the dose of 6g /kg maternal body weight /day. This dose resulted in relatively high peak blood alcohol concentration (340 mg/dl) as assessed on GD 20. A pair-fed isocaloric and untreated control groups were included. Prenatal alcohol administration retarded dams&rsquo / weight gain significantly, and had an adverse effect on pups&rsquo / weight at birth but not in adulthood. No between-group differences were observed in the litter size and in the pups&rsquo / mortality. The adult brain weight was neither affected. Pups were subjected to a series of behavioural tests as young adults (at 2.5 months of age). In adulthood, rats prenatally treated with alcohol were not impaired in sensorimotor coordination and/or did not show muscle weakness as assessed by rotarod/accelerod tests. Their behavior in the open field and plus maze suggested alcohol-induced increase in iv anxiety level and some decrease in behavioral flexibility, but hyperactivity was not observed. In cognitive tasks, alcohol treated rats showed slightly slower rate of initial place learning in the water maze. However, memory retention tested after 1 and 10-day delay, reversal learning, rate of extinction of place preference, as well as working memory capacity appeared to be the same in alcohol exposed and control rats. The possible reasons of this negative result are discussed.

The two-hit hypothesis of schizophrenia proposes that the development of the illness involves an early neurodevelopmental stress component which increases vulnerability to later stressful life events, in combination leading to overt disease. This thesis describes a two-hit animal model, comprising of an early first hit in the form of 24 hours maternal deprivation on postnatal day 9, and a late second hit simulated by 2 weeks of corticosterone administration from 8 to 10 weeks of age in rats. The project included behavioural studies on prepulse inhibition (PPI) regulation, locomotor activity, and learning and memory, and neurochemical and molecular studies on dopaminergic parameters, brain-derived neurotrophic factor (BDNF) and glucocorticoid receptor (GR) expression. / In the two-hit animals, there was little effect on baseline PPI or locomotor activity. However, the effect of acute treatment with the dopaminergic stimulants, apomorphine, amphetamine and quinpirole, was markedly diminished. There were differential effects of either maternal deprivation or corticosterone administration on the action of these drugs. However, there was no change in any of the groups in the effect of the serotonin-1A receptor agonist, 8-OH-DPAT, on PPI, or the effect of amphetamine and phencyclidine on locomotor activity. (For complete abstract open document)

<p>It has long been appreciated that the process of learning might invoke a physical change in the brain, establishing a lasting trace of experience. Recent evidence has revealed that this change manifests, at least in part, by the formation of new connections between neurons, as well as the modification of preexisting ones. This so-called structural plasticity of neural circuits – their ability to physically change in response to experience – has remained fixed as a primary point of focus in the field of neuroscience. </p><p>A large portion of this effort has been directed towards the study of dendritic spines, small protrusions emanating from neuronal dendrites that constitute the majority of recipient sites of excitatory neuronal connections. The unique, mushroom-like morphology of these tiny structures has earned them considerable attention, with even the earliest observers suggesting that their unique shape affords important functional advantages that would not be possible if synapses were to directly contact dendrites. Importantly, dendritic spines can be formed, eliminated, or structurally modified in response to both neural activity as well as learning, suggesting that their organization reflects the experience of the neural network. As such, elucidating how these structures undergo such rearrangements is of critical importance to understanding both learning and memory. </p><p>As dendritic spines are principally composed of the cytoskeletal protein actin, their formation, elimination, and modification requires biochemical signaling networks that can remodel the actin cytoskeleton. As a result, significant effort has been placed into identifying and characterizing such signaling networks and how they are controlled during synaptic activity and learning. Such efforts have highlighted Rho family GTPases – binary signaling proteins central in controlling the dynamics of the actin cytoskeleton – as attractive targets for understanding how the structural modification of spines might be controlled by synaptic activity. While much has been revealed regarding the importance of the Rho GTPases for these processes, the specific spatial and temporal features of their signals that impart such structural changes remains unclear. </p><p>The central hypotheses of the following research dissertation are as follows: first, that synaptic activity rapidly initiates Rho GTPase signaling within single dendritic spines, serving as the core mechanism of dendritic spine structural plasticity. Next, that each of the Rho GTPases subsequently expresses a spatially distinct pattern of activation, with some signals remaining highly localized, and some becoming diffuse across a region of the nearby dendrite. The diffusive signals modify the plasticity induction threshold of nearby dendritic spines, and the spatially restricted signals serve to keep the expression of plasticity specific to those spines that receive synaptic input. This combination of differentially spatially regulated signals thus equips the neuronal dendrite with the ability to perform local biochemical computations, potentially establishing an organizational preference for the arrangement of dendritic spines along a dendrite. Finally, the consequences of the differential signal patterns also help to explain several seemingly disparate properties of one of the primary upstream activators of these proteins: brain-derived neurotrophic factor (BDNF). </p><p>The first section of this dissertation describes the characterization of the activity patterns of one of the Rho family GTPases, Rac1. Using a novel Förster Resonance Energy Transfer (FRET)- based biosensor in combination with two-photon fluorescence lifetime imaging (2pFLIM) and single-spine stimulation by two-photon glutamate uncaging, the activation profile and kinetics of Rac1 during synaptic stimulation were characterized. These experiments revealed that Rac1 conveys signals to both activated spines as well as nearby, unstimulated spines that are in close proximity to the target spine. Despite the diffusion of this structural signal, however, the structural modification associated with synaptic stimulation remained restricted to the stimulated spine. Thus, Rac1 activation is not sufficient to enlarge spines, but nonetheless likely confers some heretofore-unknown function to nearby synapses. </p><p>The next set of experiments set out to detail the upstream molecular mechanisms controlling Rac1 activation. First, it was found that Rac1 activation during sLTP depends on calcium through NMDA receptors and subsequent activation of CaMKII, suggesting that Rac1 activation in this context agrees with substantial evidence linking NMDAR-CaMKII signaling to LTP in the hippocampus. Next, in light of recent evidence linking structural plasticity to another potential upstream signaling complex, BDNF-TrkB, we explored the possibility that BDNF-TrkB signaling functioned in structural plasticity via Rac1 activation. To this end, we first explored the release kinetics of BDNF and the activation kinetics of TrkB using novel biosensors in conjunction with 2p glutamate uncaging. It was found that release of BDNF from single dendritic spines during sLTP induction activates TrkB on that same spine in an autocrine manner, and that this autocrine system was necessary for both sLTP and Rac1 activation. It was also found that BDNF-TrkB signaling controls the activity of another Rho GTPase, Cdc42, suggesting that this autocrine loop conveys both synapse-specific signals (through Cdc42) and heterosynaptic signals (through Rac1). </p><p>The next set of experiments detail one the potential consequences of heterosynaptic Rac1 signaling. The spread of Rac1 activity out of the stimulated spine was found to be necessary for lowering the plasticity threshold at nearby spines, a process known as synaptic crosstalk. This was also true for the Rho family GTPase, RhoA, which shows a similar diffusive activity pattern. Conversely, the activity of Cdc42, a Rho GTPase protein whose activity is highly restricted to stimulated spines, was required only for input-specific plasticity induction. Thus, the spreading of a subset of Rho GTPase signaling into nearby spines modifies the plasticity induction threshold of these spines, increasing the likelihood that synaptic activity at these sites will induce structural plasticity. Importantly, these data suggest that the autocrine BDNF-TrkB loop described above simultaneously exerts control over both homo- and heterosynaptic structural plasticity. </p><p>The final set of experiments reveals that the spreading of GTPase activity from stimulated spines helps to overcome the high activation thresholds of these proteins to facilitate nearby plasticity. Both Rac1 and RhoA, the activity of which spread into nearby spines, showed high activation thresholds, making weak stimuli incapable of activating them. Thus, signal spreading from a strongly stimulated spine can lower the plasticity threshold at nearby spines in part by supplementing the activation of high-threshold Rho GTPases at these sites. In contrast, the highly compartmentalized Rho GTPase Cdc42 showed a very low activation threshold, and thus did not require signal spreading to achieve high levels of activity to even a weak stimulus. As a result, synaptic crosstalk elicits cooperativity of nearby synaptic events by first priming a local region of the dendrite with several (but not all) of the factors required for structural plasticity, which then allows even weak inputs to achieve plasticity by means of localized Cdc42 activation. </p><p>Taken together, these data reveal a molecular pattern whereby BDNF-dependent structural plasticity can simultaneously maintain input-specificity while also relaying heterosynaptic signals along a local stretch of dendrite via coordination of differential spatial signaling profiles of the Rho GTPase proteins. The combination of this division of spatial signaling patterns and different activation thresholds reveals a unique heterosynaptic coincidence detection mechanism that allows for cooperative expression of structural plasticity when spines are close together, which in turn provides a putative mechanism for how neurons arrange structural modifications during learning.</p> / Dissertation

abstract: Cognitive function is multidimensional and complex, and research indicates that it is impacted by age, lifetime experience, and ovarian hormone milieu. One particular domain of cognitive function that is susceptible to age-related decrements is spatial memory. Cognitive practice can affect spatial memory when aged in both males and females, and in females alone ovarian hormones have been found to alter spatial memory via modulating brain microstructure and function in many of the same brain areas affected by aging. The research in this dissertation has implications that promote an understanding of the effects of cognitive practice on aging memory, why males and females respond differently to cognitive practice, and the parameters and mechanisms underlying estrogen's effects on memory. This body of work suggests that cognitive practice can enhance memory when aged and that estrogen is a probable candidate facilitating the observed differences in the effects of cognitive practice depending on sex. This enhancement in cognitive practice effects via estrogen is supported by data demonstrating that estrogen enhances spatial memory and hippocampal synaptic plasticity. The estrogen-facilitated memory enhancements and alterations in hippocampal synaptic plasticity are at least partially facilitated via enhancements in cholinergic signaling from the basal forebrain. Finally, age, dose, and type of estrogen utilized are important factors to consider when evaluating estrogen's effects on memory and its underlying mechanisms, since age alters the responsiveness to estrogen treatment and the dose of estrogen needed, and small alterations in the molecular structure of estrogen can have a profound impact on estrogen's efficacy on memory. Collectively, this dissertation elucidates many parameters that dictate the outcome, and even the direction, of the effects that cognitive practice and estrogens have on cognition during aging. Indeed, many parameters including the ones described here are important considerations when designing future putative behavioral interventions, behavioral therapies, and hormone therapies. Ideally, the parameters described here will be used to help design the next generation of interventions, therapies, and nootropic agents that will allow individuals to maintain their cognitive capacity when aged, above and beyond what is currently possible, thus enacting lasting improvement in women's health and public health in general. / Dissertation/Thesis / Ph.D. Psychology 2011

Neste trabalho estudamos os efeitos do exercício forçado diário em esteira rolante e da exposição diária ao estresse (porque o exercício forçado envolve certo grau de estresse) durante 2 ou 8 semanas em diferentes tipos de memória em ratos Wistar machos. Os testes de memória utilizados foram: habituação da exploração em um campo aberto, reconhecimento de objetos, e memória espacial no labirinto aquático de Morris. Após estes primeiros experimentos procuramos verificar também a capacidade do exercício físico em reverter o prejuízo da memória causado pela separação maternal, procedimento que causa um déficit de memória já descrito pela literatura, utilizando, também, o teste de esquiva inibitória. O estresse diário realçou a memória de habituação, os animais aprenderam após 2 mas não após 8 semanas; houve prejuízo de memória curta (MCD) e de longa duração (MLD) na tarefa do reconhecimento em 2 semanas mas somente de MCD após 8 semanas; e não houve nenhum efeito na memória espacial após 2 ou 8 semanas. O protocolo do exercício realçou também a memória de habituação no campo aberto após 2 mas não após 8 semanas; prejudicou MCD e MLD na tarefa do reconhecimento após 2 mas não após 8 semanas; e realçou uma medida importante da aprendizagem espacial após 8 semanas (latência de escape), mas não outras medidas. Em relação ao grupo de animais que foram submetidos à separação maternal verificou-se que o exercício crônico foi capaz de reverter o déficit da MCD e MLD na esquiva inibitória e da MCD no reconhecimento de objetos, mas não teve efeitos sobre o prejuízo da MLD nesta tarefa e sobre a memória espacial testada no Labirinto Aquático de Morris. Portanto, o exercício físico crônico tem uma influência positiva sobre amemória e, adicionalmente, pode ser visto como uma ferramenta terapêutica para reverter determinados déficits de memória. / Here we studied the effects of daily forced exercise in a treadmill and of daily stress (because forced exercise involves a degree of stress) during 2 or 8 weeks on different types of memory in male Wistar rats. The memory tests were: habituation of exploration in an open field, object recognition and spatial memory in Morris water maze. After these experiments we also tried to verify the physical exercise capacity to revert the memory deficit caused by maternal deprivation, procedure that causes a memory deficit already reported, by means of the inhibitory avoidance test. Daily footshock stress enhanced habituation learning after 2 but not after 8 weeks; it hindered both short- (STM) and long-term memory (LTM) of the recognition task after 2 weeks but only STM after 8 weeks; and had no effect on the spatial task after neither 2 or 8 weeks. The exercise protocol also enhanced habituation in the open field after 2 but not 8 weeks; it hindered STM and LTM in the recognition task after 2 but not at 8 weeks; and it enhanced one important measure of spatial learning after 8 weeks (latency to escape) but not other measures. In relation of the animals that was submitted to maternal deprivation we verified that the exercise is capable to revert the deficit of STM and LTM in inhibitory avoidance test and of STM in object recognition test, but don’t have any effect on the prejudice of LTM in object recognition and in spatial memory verify using the Morris water maze test. Thus, the physical exercise had a positive influence on memory and, additionally, it can be seen like one therapeutic strategy to reverts some memory deficits.

Neste trabalho estudamos os efeitos do exercício forçado diário em esteira rolante e da exposição diária ao estresse (porque o exercício forçado envolve certo grau de estresse) durante 2 ou 8 semanas em diferentes tipos de memória em ratos Wistar machos. Os testes de memória utilizados foram: habituação da exploração em um campo aberto, reconhecimento de objetos, e memória espacial no labirinto aquático de Morris. Após estes primeiros experimentos procuramos verificar também a capacidade do exercício físico em reverter o prejuízo da memória causado pela separação maternal, procedimento que causa um déficit de memória já descrito pela literatura, utilizando, também, o teste de esquiva inibitória. O estresse diário realçou a memória de habituação, os animais aprenderam após 2 mas não após 8 semanas; houve prejuízo de memória curta (MCD) e de longa duração (MLD) na tarefa do reconhecimento em 2 semanas mas somente de MCD após 8 semanas; e não houve nenhum efeito na memória espacial após 2 ou 8 semanas. O protocolo do exercício realçou também a memória de habituação no campo aberto após 2 mas não após 8 semanas; prejudicou MCD e MLD na tarefa do reconhecimento após 2 mas não após 8 semanas; e realçou uma medida importante da aprendizagem espacial após 8 semanas (latência de escape), mas não outras medidas. Em relação ao grupo de animais que foram submetidos à separação maternal verificou-se que o exercício crônico foi capaz de reverter o déficit da MCD e MLD na esquiva inibitória e da MCD no reconhecimento de objetos, mas não teve efeitos sobre o prejuízo da MLD nesta tarefa e sobre a memória espacial testada no Labirinto Aquático de Morris. Portanto, o exercício físico crônico tem uma influência positiva sobre amemória e, adicionalmente, pode ser visto como uma ferramenta terapêutica para reverter determinados déficits de memória. / Here we studied the effects of daily forced exercise in a treadmill and of daily stress (because forced exercise involves a degree of stress) during 2 or 8 weeks on different types of memory in male Wistar rats. The memory tests were: habituation of exploration in an open field, object recognition and spatial memory in Morris water maze. After these experiments we also tried to verify the physical exercise capacity to revert the memory deficit caused by maternal deprivation, procedure that causes a memory deficit already reported, by means of the inhibitory avoidance test. Daily footshock stress enhanced habituation learning after 2 but not after 8 weeks; it hindered both short- (STM) and long-term memory (LTM) of the recognition task after 2 weeks but only STM after 8 weeks; and had no effect on the spatial task after neither 2 or 8 weeks. The exercise protocol also enhanced habituation in the open field after 2 but not 8 weeks; it hindered STM and LTM in the recognition task after 2 but not at 8 weeks; and it enhanced one important measure of spatial learning after 8 weeks (latency to escape) but not other measures. In relation of the animals that was submitted to maternal deprivation we verified that the exercise is capable to revert the deficit of STM and LTM in inhibitory avoidance test and of STM in object recognition test, but don’t have any effect on the prejudice of LTM in object recognition and in spatial memory verify using the Morris water maze test. Thus, the physical exercise had a positive influence on memory and, additionally, it can be seen like one therapeutic strategy to reverts some memory deficits.

abstract: Neurotoxicology has historically focused on substances that directly damage nervous tissue. Behavioral assays that test sensory, cognitive, or motor function are used to identify neurotoxins. But, the outcomes of behavioral assays may also be influenced by the physiological status of non-neural organs. Therefore, toxin induced damage to non- neural organs may contribute to behavioral modifications. Heavy metals and metalloids are persistent environmental pollutants and induce neurological deficits in multiple organisms. However, in the honey bee, an important insect pollinator, little is known about the sublethal effects of heavy metal and metalloid toxicity though they are exposed to these toxins chronically in some environments. In this thesis I investigate the sublethal effects of copper, cadmium, lead, and selenium on honey bee behavior and identify potential mechanisms mediating the behavioral modifications. I explore the honey bees’ ability to detect these toxins, their sensory perception of sucrose following toxin exposure, and the effects of toxin ingestion on performance during learning and memory tasks. The effects depend on the specific metal. Honey bees detect and reject copper containing solutions, but readily consume those contaminated with cadmium and lead. And, exposure to lead may alter the sensory perception of sucrose. I also demonstrate that acute selenium exposure impairs learning and long-term memory formation or recall. Localizing selenium accumulation following chronic exposure reveals that damage to non-neural organs and peripheral sensory structures is more likely than direct neurotoxicity. Probable mechanisms include gut microbiome alterations, gut lining damage, immune system activation, impaired protein function, or aberrant DNA methylation. In the case of DNA methylation, I demonstrate that inhibiting DNA methylation dynamics can impair long-term memory formation, while the nurse-to- forager transition is not altered. These experiments could serve as the bases for and reference groups of studies testing the effects of metal or metalloid toxicity on DNA methylation. Each potential mechanism provides an avenue for investigating how neural function is influenced by the physiological status of non-neural organs. And from an ecological perspective, my results highlight the need for environmental policy to consider sublethal effects in determining safe environmental toxin loads for honey bees and other insect pollinators. / Dissertation/Thesis / Doctoral Dissertation Neuroscience 2016

It was long believed within the scientific community that the adult brain was unable to generate new neurons. In the end of the 1990s the consensus changed and it is since believed that the adult brain can and does generate new neurons after birth, a process referred to as adult neurogenesis. Adult neurogenesis takes place in two places in the adult brain: the subventricular zone (SVZ) in close proximity to the olfactory bulb and the subgranular zone (SGZ) in the hippocampus. The level of adult hippocampal neurogenesis (AHN) can be upregulated and one part of the aim was to examine the effect of voluntary chronic aerobic exercise (VCAE) on AHN. It is clear that voluntary chronic aerobic exercise reliably increases AHN. Still, the function of these new brain cells is under debate. Spatial learning and memory are among the main abilities that have been focused on. The other part of the aim was to examine the effect of VCAE and AHN on spatial learning and memory. The reviewed literature suggests that both AHN and spatial learning and memory increase together from VCAE, although it does not show causation, that an increase of AHN from VCAE causally effects spatial learning and memory. More studies are needed to investigate if a causal relationship exists.

Neste trabalho estudamos os efeitos do exercício forçado diário em esteira rolante e da exposição diária ao estresse (porque o exercício forçado envolve certo grau de estresse) durante 2 ou 8 semanas em diferentes tipos de memória em ratos Wistar machos. Os testes de memória utilizados foram: habituação da exploração em um campo aberto, reconhecimento de objetos, e memória espacial no labirinto aquático de Morris. Após estes primeiros experimentos procuramos verificar também a capacidade do exercício físico em reverter o prejuízo da memória causado pela separação maternal, procedimento que causa um déficit de memória já descrito pela literatura, utilizando, também, o teste de esquiva inibitória. O estresse diário realçou a memória de habituação, os animais aprenderam após 2 mas não após 8 semanas; houve prejuízo de memória curta (MCD) e de longa duração (MLD) na tarefa do reconhecimento em 2 semanas mas somente de MCD após 8 semanas; e não houve nenhum efeito na memória espacial após 2 ou 8 semanas. O protocolo do exercício realçou também a memória de habituação no campo aberto após 2 mas não após 8 semanas; prejudicou MCD e MLD na tarefa do reconhecimento após 2 mas não após 8 semanas; e realçou uma medida importante da aprendizagem espacial após 8 semanas (latência de escape), mas não outras medidas. Em relação ao grupo de animais que foram submetidos à separação maternal verificou-se que o exercício crônico foi capaz de reverter o déficit da MCD e MLD na esquiva inibitória e da MCD no reconhecimento de objetos, mas não teve efeitos sobre o prejuízo da MLD nesta tarefa e sobre a memória espacial testada no Labirinto Aquático de Morris. Portanto, o exercício físico crônico tem uma influência positiva sobre amemória e, adicionalmente, pode ser visto como uma ferramenta terapêutica para reverter determinados déficits de memória. / Here we studied the effects of daily forced exercise in a treadmill and of daily stress (because forced exercise involves a degree of stress) during 2 or 8 weeks on different types of memory in male Wistar rats. The memory tests were: habituation of exploration in an open field, object recognition and spatial memory in Morris water maze. After these experiments we also tried to verify the physical exercise capacity to revert the memory deficit caused by maternal deprivation, procedure that causes a memory deficit already reported, by means of the inhibitory avoidance test. Daily footshock stress enhanced habituation learning after 2 but not after 8 weeks; it hindered both short- (STM) and long-term memory (LTM) of the recognition task after 2 weeks but only STM after 8 weeks; and had no effect on the spatial task after neither 2 or 8 weeks. The exercise protocol also enhanced habituation in the open field after 2 but not 8 weeks; it hindered STM and LTM in the recognition task after 2 but not at 8 weeks; and it enhanced one important measure of spatial learning after 8 weeks (latency to escape) but not other measures. In relation of the animals that was submitted to maternal deprivation we verified that the exercise is capable to revert the deficit of STM and LTM in inhibitory avoidance test and of STM in object recognition test, but don’t have any effect on the prejudice of LTM in object recognition and in spatial memory verify using the Morris water maze test. Thus, the physical exercise had a positive influence on memory and, additionally, it can be seen like one therapeutic strategy to reverts some memory deficits.

This dissertation describes separate but related studies that explore visual spatial learning and memory in Fragile X Syndrome. Across all studies, either the performance of individuals affected by FXS and/or fmr1 KO mice was compared to comparison controls on seven H-W mazes of increasing difficulty levels. Study one employed the traditional configuration of the H-W mazes to evaluate performance variables that include latency to complete the maze and number of the errors. The results of study 1 revealed significant differences in performance for both FXS groups as compared to mental age-matched comparison individuals and wild type mice, respectively. In contrast to the FXS group, performance of the comparison group improved as indicated by significantly fewer errors across trials. A similar pattern of results was observed when latency across trials was analyzed. Taken together, the results of study one support the hypothesis that a selective deficit in spatial learning and memory characteristic of the FXS phenotype can be observed in the murine model of FXS, if equivalent tasks are employed in testing humans and mice. Study two expanded on these findings by adding landmarks to the maze environment to evaluate how these may impact spatial learning and memory in fmr1 KO mice. Contrary to our hypotheses, landmarks significantly impaired wild type control performance. In addition, results revealed that the performance of the fmr1 KO mice generally did not differ between landmark and non-landmark tasks, indicating that the presence of landmarks neither enhanced nor hindered mouse performance. Lastly, study three entailed a more in-depth behavior analysis of maze navigation performance for FXS individuals from study 1. Consistent with the hypotheses and findings from study 1, results revealed significant differences in performance variables between individuals, with FXS participants generally performing worse than the comparison group participants. Taken together, the results of study 3 generally supported the hypothesis that there was greater impairment in performance for individuals affected by FXS as compared to controls. This impairment was evident in the pattern of pathways taken to solve H-W mazes, consistent with the notion that affected individuals employed different behavioral strategies.