Cholinergic enhancement of perceptual learning : behavioral, physiological, and neuro-pharmacological study in the rat primary visual cortex

Les cortices sensoriels sont des régions cérébrales essentielles pour la perception. En particulier, le cortex visuel traite l’information visuelle en provenance de la rétine qui transite par le thalamus. Les neurones sont les unités fonctionnelles qui transforment l'information sensorielle en signaux électriques, la transfèrent vers le cortex et l'intègrent. Les neurones du cortex visuel sont spécialisés et analysent différents aspects des stimuli visuels. La force des connections entre les neurones peut être modulée par la persistance de l'activité pré-synaptique et induit une augmentation ou une diminution du signal post-synaptique à long terme. Ces modifications de la connectivité synaptique peuvent induire la réorganisation de la carte corticale, c’est à dire la représentation de ce stimulus et la puissance de son traitement cortical. Cette réorganisation est connue sous le nom de plasticité corticale. Elle est particulièrement active durant la période de développement, mais elle s’observe aussi chez l’adulte, par exemple durant l’apprentissage. Le neurotransmetteur acétylcholine (ACh) est impliqué dans de nombreuses fonctions cognitives telles que l’apprentissage ou l’attention et il est important pour la plasticité corticale. En particulier, les récepteurs nicotiniques et muscariniques du sous-type M1 et M2 sont les récepteurs cholinergiques impliqués dans l’induction de la plasticité corticale. L’objectif principal de la présente thèse est de déterminer les mécanismes de plasticité corticale induits par la stimulation du système cholinergique au niveau du télencéphale basal et de définir les effets sur l’amélioration de la perception sensorielle. Afin d’induire la plasticité corticale, j’ai jumelé des stimulations visuelles à des injections intracorticales d’agoniste cholinergique (carbachol) ou à une stimulation du télencéphale basal (neurones cholinergiques qui innervent le cortex visuel primaire). J'ai analysé les potentiels évoqués visuels (PEVs) dans le cortex visuel primaire des rats pendant 4 à 8 heures après le couplage. Afin de préciser l’action de l’ACh sur l’activité des PEVs dans V1, j’ai injecté individuellement l’antagoniste des récepteurs muscariniques, nicotiniques, α7 ou NMDA avant l’infusion de carbachol. La stimulation du système cholinergique jumelée avec une stimulation visuelle augmente l’amplitude des PEVs durant plus de 8h. Le blocage des récepteurs muscarinique, nicotinique et NMDA abolit complètement cette amélioration, tandis que l’inhibition des récepteurs α7 a induit une augmentation instantanée des PEVs. Ces résultats suggèrent que l'ACh facilite à long terme la réponse aux stimuli visuels et que cette facilitation implique les récepteurs nicotiniques, muscariniques et une interaction avec les récepteur NMDA dans le cortex visuel. Ces mécanismes sont semblables à la potentiation à long-terme, évènement physiologique lié à l’apprentissage. L’étape suivante était d’évaluer si l’effet de l’amplification cholinergique de l’entrée de l’information visuelle résultait non seulement en une modification de l’activité corticale mais aussi de la perception visuelle. J’ai donc mesuré l’amélioration de l’acuité visuelle de rats adultes éveillés exposés durant 10 minutes par jour pendant deux semaines à un stimulus visuel de type «réseau sinusoïdal» couplé à une stimulation électrique du télencéphale basal. L’acuité visuelle a été mesurée avant et après le couplage des stimulations visuelle et cholinergique à l’aide d’une tâche de discrimination visuelle. L’acuité visuelle du rat pour le stimulus d’entrainement a été augmentée après la période d’entrainement. L’augmentation de l’acuité visuelle n’a pas été observée lorsque la stimulation visuelle seule ou celle du télencéphale basal seul, ni lorsque les fibres cholinergiques ont été lésées avant la stimulation visuelle. Une augmentation à long terme de la réactivité corticale du cortex visuel primaire des neurones pyramidaux et des interneurones GABAergiques a été montrée par l’immunoréactivité au c-Fos. Ainsi, lorsque couplé à un entrainement visuel, le système cholinergique améliore les performances visuelles pour l’orientation et ce probablement par l’optimisation du processus d’attention et de plasticité corticale dans l’aire V1. Afin d’étudier les mécanismes pharmacologiques impliqués dans l’amélioration de la perception visuelle, j’ai comparé les PEVs avant et après le couplage de la stimulation visuelle/cholinergique en présence d’agonistes/antagonistes sélectifs. Les injections intracorticales des différents agents pharmacologiques pendant le couplage ont montré que les récepteurs nicotiniques et M1 muscariniques amplifient la réponse corticale tandis que les récepteurs M2 muscariniques inhibent les neurones GABAergiques induisant un effet excitateur. L’infusion d’antagoniste du GABA corrobore l’hypothèse que le système inhibiteur est essentiel pour induire la plasticité corticale. Ces résultats démontrent que l’entrainement visuel jumelé avec la stimulation cholinergique améliore la plasticité corticale et qu’elle est contrôlée par les récepteurs nicotinique et muscariniques M1 et M2. Mes résultats suggèrent que le système cholinergique est un système neuromodulateur qui peut améliorer la perception sensorielle lors d’un apprentissage perceptuel. Les mécanismes d’amélioration perceptuelle induits par l’acétylcholine sont liés aux processus d’attention, de potentialisation à long-terme et de modulation de la balance d’influx excitateur/inhibiteur. En particulier, le couplage de l’activité cholinergique avec une stimulation visuelle augmente le ratio de signal / bruit et ainsi la détection de cibles. L’augmentation de la concentration cholinergique corticale potentialise l’afférence thalamocorticale, ce qui facilite le traitement d’un nouveau stimulus et diminue la signalisation cortico-corticale minimisant ainsi la modulation latérale. Ceci est contrôlé par différents sous-types de récepteurs cholinergiques situés sur les neurones GABAergiques ou glutamatergiques des différentes couches corticales. La présente thèse montre qu’une stimulation électrique dans le télencéphale basal a un effet similaire à l’infusion d’agoniste cholinergique et qu’un couplage de stimulations visuelle et cholinergique induit la plasticité corticale. Ce jumelage répété de stimulations visuelle/cholinergique augmente la capacité de discrimination visuelle et améliore la perception. Cette amélioration est corrélée à une amplification de l’activité neuronale démontrée par immunocytochimie du c-Fos. L’immunocytochimie montre aussi une différence entre l’activité des neurones glutamatergiques et GABAergiques dans les différentes couches corticales. L’injection pharmacologique pendant la stimulation visuelle/cholinergique suggère que les récepteurs nicotiniques, muscariniques M1 peuvent amplifier la réponse excitatrice tandis que les récepteurs M2 contrôlent l’activation GABAergique. Ainsi, le système cholinergique activé au cours du processus visuel induit des mécanismes de plasticité corticale et peut ainsi améliorer la capacité perceptive. De meilleures connaissances sur ces actions ouvrent la possibilité d’accélérer la restauration des fonctions visuelles lors d’un déficit ou d’amplifier la fonction cognitive.

Frequency of infant stroking reported by mothers moderates the effect of prenatal depression on infant behavioural and physiological outcomes

Animal studies find that prenatal stress is associated with increased physiological and emotional reactivity later in life, mediated via fetal programming of the HPA axis through decreased glucocorticoid receptor (GR) gene expression. Post-natal behaviours, notably licking and grooming in rats, cause decreased behavioural indices of fear and reduced HPA axis reactivity mediated via increased GR gene expression. Post-natal maternal behaviours may therefore be expected to modify prenatal effects, but this has not previously been examined in humans. We examined whether, according to self-report, maternal stroking over the first weeks of life modified associations between prenatal depression and physiological and behavioral outcomes in infancy, hence mimicking effects of rodent licking and grooming. From a general population sample of 1233 first time mothers recruited at 20 weeks gestation we drew a stratified random sample of 316 for assessment at 32 weeks based on reported inter-partner psychological abuse, a risk to child development. Of these 271 provided data at 5, 9 and 29 weeks post delivery. Mothers reported how often they stroked their babies at 5 and 9 weeks. At 29 weeks vagal withdrawal to a stressor, a measure of physiological adaptability, and maternal reported negative emotionality were assessed. There was a significant interaction between prenatal depression and maternal stroking in the prediction of vagal reactivity to a stressor (p = .01), and maternal reports of infant anger proneness (p = .007) and fear (p = .043). Increasing maternal depression was associated with decreasing physiological adaptability, and with increasing negative emotionality, only in the presence of low maternal stroking. These initial findings in humans indicate that maternal stroking in infancy, as reported by mothers, has effects strongly resembling the effects of observed maternal behaviours in animals, pointing to future studies of the epigenetic, physiological and behavioral effects of maternal stroking.

Development of Clinical Decision Support Systems based on Mathematical Models of Physiological Systems

In the last years of research, I focused my studies on different physiological problems. Together with my supervisors, I developed/improved different mathematical models in order to create valid tools useful for a better understanding of important clinical issues. The aim of all this work is to develop tools for learning and understanding cardiac and cerebrovascular physiology as well as pathology, generating research questions and developing clinical decision support systems useful for intensive care unit patients. I. ICP-model Designed for Medical Education We developed a comprehensive cerebral blood flow and intracranial pressure model to simulate and study the complex interactions in cerebrovascular dynamics caused by multiple simultaneous alterations, including normal and abnormal functional states of auto-regulation of the brain. Individual published equations (derived from prior animal and human studies) were implemented into a comprehensive simulation program. Included in the normal physiological modelling was: intracranial pressure, cerebral blood flow, blood pressure, and carbon dioxide (CO2) partial pressure. We also added external and pathological perturbations, such as head up position and intracranial haemorrhage. The model performed clinically realistically given inputs of published traumatized patients, and cases encountered by clinicians. The pulsatile nature of the output graphics was easy for clinicians to interpret. The manoeuvres simulated include changes of basic physiological inputs (e.g. blood pressure, central venous pressure, CO2 tension, head up position, and respiratory effects on vascular pressures) as well as pathological inputs (e.g. acute intracranial bleeding, and obstruction of cerebrospinal outflow). Based on the results, we believe the model would be useful to teach complex relationships of brain haemodynamics and study clinical research questions such as the optimal head-up position, the effects of intracranial haemorrhage on cerebral haemodynamics, as well as the best CO2 concentration to reach the optimal compromise between intracranial pressure and perfusion. We believe this model would be useful for both beginners and advanced learners. It could be used by practicing clinicians to model individual patients (entering the effects of needed clinical manipulations, and then running the model to test for optimal combinations of therapeutic manoeuvres). II. A Heterogeneous Cerebrovascular Mathematical Model Cerebrovascular pathologies are extremely complex, due to the multitude of factors acting simultaneously on cerebral haemodynamics. In this work, the mathematical model of cerebral haemodynamics and intracranial pressure dynamics, described in the point I, is extended to account for heterogeneity in cerebral blood flow. The model includes the Circle of Willis, six regional districts independently regulated by autoregulation and CO2 reactivity, distal cortical anastomoses, venous circulation, the cerebrospinal fluid circulation, and the intracranial pressure-volume relationship. Results agree with data in the literature and highlight the existence of a monotonic relationship between transient hyperemic response and the autoregulation gain. During unilateral internal carotid artery stenosis, local blood flow regulation is progressively lost in the ipsilateral territory with the presence of a steal phenomenon, while the anterior communicating artery plays the major role to redistribute the available blood flow. Conversely, distal collateral circulation plays a major role during unilateral occlusion of the middle cerebral artery. In conclusion, the model is able to reproduce several different pathological conditions characterized by heterogeneity in cerebrovascular haemodynamics and can not only explain generalized results in terms of physiological mechanisms involved, but also, by individualizing parameters, may represent a valuable tool to help with difficult clinical decisions. III. Effect of Cushing Response on Systemic Arterial Pressure. During cerebral hypoxic conditions, the sympathetic system causes an increase in arterial pressure (Cushing response), creating a link between the cerebral and the systemic circulation. This work investigates the complex relationships among cerebrovascular dynamics, intracranial pressure, Cushing response, and short-term systemic regulation, during plateau waves, by means of an original mathematical model. The model incorporates the pulsating heart, the pulmonary circulation and the systemic circulation, with an accurate description of the cerebral circulation and the intracranial pressure dynamics (same model as in the first paragraph). Various regulatory mechanisms are included: cerebral autoregulation, local blood flow control by oxygen (O2) and/or CO2 changes, sympathetic and vagal regulation of cardiovascular parameters by several reflex mechanisms (chemoreceptors, lung-stretch receptors, baroreceptors). The Cushing response has been described assuming a dramatic increase in sympathetic activity to vessels during a fall in brain O2 delivery. With this assumption, the model is able to simulate the cardiovascular effects experimentally observed when intracranial pressure is artificially elevated and maintained at constant level (arterial pressure increase and bradicardia). According to the model, these effects arise from the interaction between the Cushing response and the baroreflex response (secondary to arterial pressure increase). Then, patients with severe head injury have been simulated by reducing intracranial compliance and cerebrospinal fluid reabsorption. With these changes, oscillations with plateau waves developed. In these conditions, model results indicate that the Cushing response may have both positive effects, reducing the duration of the plateau phase via an increase in cerebral perfusion pressure, and negative effects, increasing the intracranial pressure plateau level, with a risk of greater compression of the cerebral vessels. This model may be of value to assist clinicians in finding the balance between clinical benefits of the Cushing response and its shortcomings. IV. Comprehensive Cardiopulmonary Simulation Model for the Analysis of Hypercapnic Respiratory Failure We developed a new comprehensive cardiopulmonary model that takes into account the mutual interactions between the cardiovascular and the respiratory systems along with their short-term regulatory mechanisms. The model includes the heart, systemic and pulmonary circulations, lung mechanics, gas exchange and transport equations, and cardio-ventilatory control. Results show good agreement with published patient data in case of normoxic and hyperoxic hypercapnia simulations. In particular, simulations predict a moderate increase in mean systemic arterial pressure and heart rate, with almost no change in cardiac output, paralleled by a relevant increase in minute ventilation, tidal volume and respiratory rate. The model can represent a valid tool for clinical practice and medical research, providing an alternative way to experience-based clinical decisions. In conclusion, models are not only capable of summarizing current knowledge, but also identifying missing knowledge. In the former case they can serve as training aids for teaching the operation of complex systems, especially if the model can be used to demonstrate the outcome of experiments. In the latter case they generate experiments to be performed to gather the missing data.

Taiji practice attenuates psychobiological stress reactivity - A randomized controlled trial in healthy subjects

Background: Stress reducing effects of Taiji, a mindful and gentle form of body movement, have been reported in previous studies, but standardized and controlled experimental studies are scarce. The present study investigates the effect of regular Taiji practice on psychobiological stress response in healthy men and women. Methods: 70 participants were randomly assigned to either Taiji classes or a waiting list. After 3 months, 26 (8 men, 18 women) persons in the Taiji group and 23 (9 men, 14 women) in the waiting control group underwent a standardized psychosocial stress test combining public speaking and mental arithmetic in front of an audience. Salivary cortisol and α-amylase, heart rate, and psychological responses to psychosocial stress were compared between the study groups. (ClinicalTrials.gov number, NCT01122706.) Results: Stress induced characteristic changes in all psychological and physiological measures. Compared to controls, Taiji participants exhibited a significantly lower stress reactivity of cortisol (p = .028) and heart rate (p = .028), as well as lower α-amylase levels (p = .049). They reported a lower increase in perceived stressfulness (p = .006) and maintained a higher level of calmness (p = .019) in response to psychosocial stress. Conclusion: Our results consistently suggest that practicing Taiji attenuates psychobiological stress reactivity in healthy subjects. This may underline the role of Taiji as a useful mind–body practice for stress prevention.

A Measurement Model of Cortisol Reactivity of Healthy Older Adults

Research on the physiological adaptation process has found that stress is associated with the rate of cortisol secretion, the main hormone that reflects stress. However, considerable variation among subjects has been reported. Using a sample of older adults (N=46), we tested the hypothesis that cortisol reactivity is composed of (1) a situation-related component representing hypothalamic influence on cortisol secretion observed on three different occasions, and (2) a stable component representing a general trait responsible for cortisol responses observed from occasion to occasion. LISREL VIII was used to test this hypothesis. Results indicated that a homogeneous reliability model was not supported by the data. A congeneric measurement model represented a better fit to the data. Results suggest that subjects have consistent patterns of response during separate experimental occasions. However, results do not suggest a consistent pattern of response over time. The main implication of these results is that salivary cortisol measures are sensitive to experimental stress situations. As such, this noninvasive method may be useful in examining adaptive responses to stress.

Low social support and poor emotional regulation are associated with increased stress hormone reactivity to mental stress in systemic hypertension

CONTEXT: There is strong evidence for a physiological hyperreactivity to stress in systemic hypertension, but data on associated or potentially moderating psychological factors are scarce. OBJECTIVE: The objective of the study was to identify psychological correlates of physiological stress reactivity in systemic hypertension. DESIGN: This was a cross-sectional, quasi-experimentally controlled study. Study participants underwent an acute standardized psychosocial stress task combining public speaking and mental arithmetic in front of an audience. SETTING: The study was conducted in the population in the state of Zurich, Switzerland. SUBJECTS: Subjects included 22 hypertensive and 26 normotensive men (mean +/- sem 44 +/- 2 yr). MAIN OUTCOME MEASURES: We assessed the psychological measures social support, emotional regulation, and cognitive appraisal of the stressful situation. Moreover, we measured salivary cortisol and plasma epinephrine and norepinephrine before and after stress and several times up to 60 min thereafter as well as blood pressure and heart rate. RESULTS: We found poorer hedonistic emotional regulation (HER) and lower perceived social support in hypertensives, compared with normotensives (P < 0.01). Compared with normotensives, hypertensives showed higher cortisol, epinephrine, and norepinephrine secretions after stress (P < 0.038) as well as higher systolic and diastolic blood pressure (P < 0.001). Cortisol reactivity and norepinephrine secretion were highest in hypertensive men with low HER (P < 0.05). In contrast, hypertensives with high HER did not significantly differ from normotensives in both cortisol and norepinephrine secretion after stress. Epinephrine secretion was highest in hypertensives with low social support but was not different between hypertensives with high social support and normotensives. CONCLUSIONS: The findings suggest that both low social support and low HER are associated with elevated stress hormone reactivity in systemic hypertension.

Exercise and Mood: Exploring the Role of Exercise in Regulating Stress Reactivity in Bipolar Disorder

Bipolar Disorder (BD) is a recurrent and debilitating psychological disorder characterized by a chronic dysregulation of mood with fluctuations between extremely low (e.g., depression) and extremely elevated mood states (e.g., mania), and ranks as the 6th leading cause of disability in the world. Although research has consistently shown that exercise may have antidepressant and stress-attenuating benefits in other psychiatric illnesses (e.g., depression, anxiety), these benefits have not been directly investigated for BD. The current study represents the first known investigation to examine this relationship. Single-participant designs, with crossover and interaction treatment components (i.e., A/B/A/B/A, A/C/A/C/A, A/B/A/C/A, or A/C/A/B/A) were utilized to investigate the impact of participation in a prescribed regimen of exercise (EP) versus standard behavioral activation (SBA; i.e., non-exercise activity) has on stress perception and reactivity, and mood stability in a sample of individuals with BD. Individuals completed four total weeks of treatment, and psychophysiological measures of reactivity were recorded during a laboratory stress task (i.e., backward counting task) prior to and following each two-week intervention phase. No appreciable differences were found between levels of exercise participation between treatment groups. Interestingly, symptoms of depressed mood (BDI-II scores) decreased at similar rates following 4 weeks of treatment for all participants. BDI-II decreases were found to be most correlated with elective exercise participation, although this relationship was not significant. Regarding stress reactivity, elective participation in mild to moderate intensity exercise was found to reduce an individual’s perception of stress reactivity to an acute stressor, while participation in a prescribed program of exercise was more effective in reducing physiological response to the same task. Utilizing multiple forms of behavioral activation simultaneously was found to be most effective in decreasing perception of stress reactivity, and may also result in a positive change in the use of adaptive versus maladaptive coping strategies. Participation in a 4-week program of exercise appeared to provide the most benefit, consistent with exercise habituation theories. Overall, current findings provide preliminary support for the prophylactic benefits of including a prescribed and monitored program of exercise as an adjunct treatment for individuals with BD. Larger scale research is needed to more clearly determine the impact of exercise on stress reactivity and mood episode relapse in individuals with BD.

Electron transfer in acetohydroxy acid synthase as a side reaction of catalysis. implications for the reactivity and partitioning of the carbanion/enamine form of (alpha-hydroxyethyl)thiamin diphosphate in a "nonredox" flavoenzyme

Acetohydroxy acid synthases (AHAS) are thiamin diphosphate- (ThDP-) and FAD-dependent enzymes that catalyze the first common step of branched-chain amino acid biosynthesis in plants, bacteria, and fungi. Although the flavin cofactor is not chemically involved in the physiological reaction of AHAS, it has been shown to be essential for the structural integrity and activity of the enzyme. Here, we report that the enzyme-bound FAD in AHAS is reduced in the course of catalysis in a side reaction. The reduction of the enzyme-bound flavin during turnover of different substrates under aerobic and anaerobic conditions was characterized by stopped-flow kinetics using the intrinsic FAD absorbance. Reduction of enzyme-bound FAD proceeds with a net rate constant of k' = 0.2 s(-1) in the presence of oxygen and approximately 1 s(-1) under anaerobic conditions. No transient flavin radicals are detectable during the reduction process while time-resolved absorbance spectra are recorded. Reconstitution of the binary enzyme-FAD complex with the chemically synthesized intermediate 2-(hydroxyethyl)-ThDP also results in a reduction of the flavin. These data provide evidence for the first time that the key catalytic intermediate 2-(hydroxyethyl)ThDP in the carbanionic/enamine form is not only subject to covalent addition of 2-keto acids and an oxygenase side reaction but also transfers electrons to the adjacent FAD in an intramolecular redox reaction yielding 2-acetyl-ThDP and reduced FAD. The detection of the electron transfer supports the idea of a common ancestor of acetohydroxy acid synthase and pyruvate oxidase, a homologous ThDP- and FAD-dependent enzyme that, in contrast to AHASs, catalyzes a reaction that relies on intercofactor electron transfer.

Covariation and interference between physiological reflexes: Eye-blink startle cardiac defense, and skin conductance

Comparative studies of autonomic and somatic reflexes, such as cardiac defense and motor startle, are rare. However, examination of the pattern of covariation, independence, or interference among physiological reflexes may help to clarify their functional significance and elucidate their complex modulation by psychological factors. Here we report the results of a study that examined the pattern of interference of eye-blink startle on subsequent cardiac defense. Participants were 63 students (31 women) distributed into three groups according to the sensory modality of the eliciting stimulus during the startle trials: acoustic high intensity (105 dB), acoustic low intensity (65 dB), and visual modality. Startle trials consisted of 12 presentations of the eliciting stimulus with a duration of 50 ms, instantaneous risetime, and a variable inter-stimulus interval of 16 – 20 s.Defense trials began 20 s after the last startle trial and consisted, for all groups, of 3 presentations of the high intensity acoustic stimulus with a duration of 500 ms and an inter-stimulus interval of 215 s. Results showed a clear interference of the startle trials on the subsequent defense trials when both types of trials shared identical sensory modality (acoustic) independently of intensity: the expected pattern of cardiac defense in the first trial only appeared in the visual modality. Similar interference effects were observed in the skin conductance response. Subjective reactivity to the defense stimulus did not detect differences between conditions.

Biometric and physiological factors in human ocular perfusion

By addressing the vascular features that characterise myopia, this thesis aims to provide an understanding of the early structural changes associated with human myopia and the progression to co-morbidity with age. This thesis addresses three main areas of study: 1. Ocular perfusion features and autoregulatory mechanisms in human myopia; 2. Choroidal thickness at the macular area of myopic eyes; 3. Effect of chronic smoking on the ocular haemodynamics and autoregulation. This thesis demonstrated a reduced resting ocular pulse amplitude and retrobulbar blood flow in human myopia, associated with an apparent oversensitivity to the vasodilatory effects of hypercapnia, which may be due to anatomical differences in the volume of the vessel beds. In young smokers, normal resting state vascular characteristics were present; however there also appeared to be increased reactivity to hypercapnia, possibly due to relative chronic hypoxia. The systemic circulation in myopes and smokers over-reacted similarly to hypercapnia suggesting that physiologic differences are not confined to the eye. Age also showed a negative effect on autoregulatory capacity in otherwise normal eyes. Collectively, these findings suggest that myopes and smokers require greater autoregulatory capacity to maintain appropriate oxygenation of retinal tissue, and since the capacity for such regulation reduces with age, these groups are at greater risk of insufficient autoregulation and relative hypoxia with age.

Development of Effortful Control as a Moderator of the Longitudinal Relations of Negative Reactivity and Symptoms in Preschool

Thesis (Ph.D.)--University of Washington, 2016-08

Cortisol Reactivity and Observed Parenting among Mothers of Children with and without ADHD

Parenting is a robust predictor of developmental outcomes among children with ADHD. Early parenting predicts the persistence and course of ADHD and comorbid problems above and beyond risk associated with shared genetic effects. Yet, on average, mothers of children with ADHD are less positive and more negative in their parent-child interactions compared to mothers of non-disordered children. Little is known about psychobiological markers which may be associated with individual variations in maternal parenting in families of children with ADHD. Neurobiological models of parenting suggest that maternal cortisol levels following a stressor may be positively associated with hostile and intrusive parenting; however, to date no studies have examined maternal cortisol reactivity and parenting in school-age, or clinical samples of, children. Mothers’ regulation of physiological stress responses may be particularly important for families of children with ADHD, as parenting a child with chronically challenging behaviors represents a persistent environmental stressor. The current study sought to extend the existing literature by providing an empirical examination of the relationship between maternal cortisol reactivity following two laboratory stressors and parenting among mothers of children with and without ADHD. It was hypothesized that child ADHD group would moderate the relationship between cortisol reactivity and self-reported and observed parenting. Greater total cortisol output and greater increase in cortisol during the TSST were associated with decreased positive parenting and increased negative and directive parenting, with the exception of parental involvement, which was associated with increased cortisol output during the TSST. Conversely, cortisol output during the PCI was associated with increased positive parenting, increased parental involvement, and decreased negative parenting. In contrast to the TSST, a greater decrease in cortisol during the PCI indicated more positive parenting and parental involvement. These associations were specific to mothers of children with ADHD, with the exception of maternal directiveness, which was specific to comparison mothers. Findings add to our understanding of physiological processes associated with maternal parenting and contribute to an integrative biological, psychological, and cognitive process model of parenting in families of children with ADHD.

Effect Of Pitavastatin On Vascular Reactivity In Hypercholesterolemic Rabbits.

Pitavastatin is the newest statin available in Brazil and likely the one with fewer side effects. Thus, pitavastatin was evaluated in hypercholesterolemic rabbits in relation to its action on vascular reactivity. To assess the lowest dose of pitavastatin necessary to reduce plasma lipids, cholesterol and tissue lipid peroxidation, as well as endothelial function in hypercholesterolemic rabbits. Thirty rabbits divided into six groups (n = 5): G1 - standard chow diet; G2 - hypercholesterolemic diet for 30 days; G3 - hypercholesterolemic diet and after the 16th day, diet supplemented with pitavastatin (0.1 mg); G4 - hypercholesterolemic diet supplemented with pitavastatin (0.25 mg); G5 - hypercholesterolemic diet supplemented with pitavastatin (0.5 mg); G6 - hypercholesterolemic diet supplemented with pitavastatin (1.0 mg). After 30 days, total cholesterol, HDL, triglycerides, glucose, creatine kinase (CK), aspartate aminotransferase (AST), alanine aminotransferase (ALT) were measured and LDL was calculated. In-depth anesthesia was performed with sodium thiopental and aortic segments were removed to study endothelial function, cholesterol and tissue lipid peroxidation. The significance level for statistical tests was 5%. Total cholesterol and LDL were significantly elevated in relation to G1. HDL was significantly reduced in G4, G5 and G6 when compared to G2. Triglycerides, CK, AST, ALT, cholesterol and tissue lipid peroxidation showed no statistical difference between G2 and G3-G6. Significantly endothelial dysfunction reversion was observed in G5 and G6 when compared to G2. Pitavastatin starting at a 0.5 mg dose was effective in reverting endothelial dysfunction in hypercholesterolemic rabbits.

Impact Of Pregabalin Treatment On Synaptic Plasticity And Glial Reactivity During The Course Of Experimental Autoimmune Encephalomyelitis.

Multiple sclerosis (MS) is an autoimmune and neurodegenerative disease that affects young adults. It is characterized by generating a chronic demyelinating autoimmune inflammation in the central nervous system. An experimental model for studying MS is the experimental autoimmune encephalomyelitis (EAE), induced by immunization with antigenic proteins from myelin. The present study investigated the evolution of EAE in pregabalin treated animals up to the remission phase. The results demonstrated a delay in the onset of the disease with statistical differences at the 10th and the 16th day after immunization. Additionally, the walking track test (CatWalk) was used to evaluate different parameters related to motor function. Although no difference between groups was obtained for the foot print pressure, the regularity index was improved post treatment, indicating a better motor coordination. The immunohistochemical analysis of putative synapse preservation and glial reactivity revealed that pregabalin treatment improved the overall morphology of the spinal cord. A preservation of circuits was depicted and the glial reaction was downregulated during the course of the disease. qRT-PCR data did not show immunomodulatory effects of pregabalin, indicating that the positive effects were restricted to the CNS environment. Overall, the present data indicate that pregabalin is efficient for reducing the seriousness of EAE, delaying its course as well as reducing synaptic loss and astroglial reaction.

Mesenchymal Stem Cells Engrafted In A Fibrin Scaffold Stimulate Schwann Cell Reactivity And Axonal Regeneration Following Sciatic Nerve Tubulization.

The present study investigated the effectiveness of mesenchymal stem cells (MSCs) associated with a fibrin scaffold (FS) for the peripheral regenerative process after nerve tubulization. Adult female Lewis rats received a unilateral sciatic nerve transection followed by repair with a polycaprolactone (PCL)-based tubular prosthesis. Sixty days after injury, the regenerated nerves were studied by immunohistochemistry. Anti-p75NTR immunostaining was used to investigate the reactivity of the MSCs. Basal labeling, which was upregulated during the regenerative process, was detected in uninjured nerves and was significantly greater in the MSC-treated group. The presence of GFP-positive MSCs was detected in the nerves, indicating the long term survival of such cells. Moreover, there was co-localization between MSCs and BNDF immunoreactivity, showing a possible mechanism by which MSCs improve the reactivity of SCs. Myelinated axon counting and morphometric analyses showed that MSC engrafting led to a higher degree of fiber compaction combined with a trend of increased myelin sheath thickness, when compared with other groups. The functional result of MSC engrafting was that the animals showed higher motor function recovery at the seventh and eighth week after lesion. The findings herein show that MSC+FS therapy improves the nerve regeneration process by positively modulating the reactivity of SCs.