Title from title page of PDF (University of Missouri--St. Louis, viewed Mar. 3, 2010). Includes bibliographical references (p. 113-127).

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Das Rett Syndrom (RTT) gehört zu den tiefgreifenden Entwicklungsstörungen des Gehirns von dem fast ausschließlich Mädchen betroffen sind (ICD-10, F84.10). Ursächlich für die Pathogenese sind Mutationen im X-chromsomalen MECP2-Gen, welches für den Transkriptionsfaktor Methyl-CpG binding protein 2 (MeCP2) kodiert. Unterschiedliche neurologische Symptome treten zwischen 6 und 18 Monaten nach der Geburt auf, wobei schwere Rhythmussstörungen der Atmung für ein Viertel plötzlicher Todesfälle bei Rett-Patientinnen verantwortlich gemacht werden. Der neuronale Atmungsrhythmus bei Säugern wird in verschieden Regionen des ponto-medullären Hirnstammes generiert, wobei der Prä-Bötzinger Komplex als essentiell für die Rhythmogenese der Atmung angesehen wird. Mittels Genexpressionsstudien in der Ventralen Respiratorischen Gruppe (VRG), die den Prä-Bötzinger-Komplex einschließt, zeigte sich eine massiv erhöhte, pathologische Expression des Serotoninrezeptor 5B sowohl auf mRNA-, als auch auf Proteinebene bei MeCP2-defizienten Mäusen zum postnatalen Entwicklungstag P40. Der Serotoninrezeptor 5B (5-HTR5B) gehört zur Klasse der G-Protein-gekoppelten Rezeptoren. Durch detaillierte Analysen des 5-HTR5B-Proteins konnte eine natürliche Trunkierung des Rezeptors nachgewiesen werden. Des Weiteren wurde eine ungewöhnliche intrazelluläre Lokalisierung in Membranen von vesikulären und tubulären Kompartimenten beobachtet. Trotz dieser ungewöhnlichen Eigenschaften besitzt der Rezeptor weiterhin die Fähigkeit, das inhibitorische G-Protein Gαi3 konstitutiv zu aktivieren und somit den Anstieg von cAMP zu verhindern. Durch genetisches Ausschalten des 5-HTR5B Proteins (knockout) konnte gezeigt werden, dass die durch 5-HTR5B-verminderte cAMP-Konzentration in der VRG ursächlich für den gestörten Atmungsrhythmus MeCP2-defizienter Mäuse ist. Die sich aus diesen Ergebnissen ableitende pharmakologische Strategie, die cAMP Konzentration zu erhöhen, führte zu einem deutlich verbesserten Atmungsrhythmus. Die Ergebnisse dieser Arbeit implizieren neue Therapieansätze zur Behandlung der Atmungs-störungen von Rett-Patienten.

Certains gènes, modulant la sérotonine (5-hydroxytryptamine, 5-HT), ont été associés aux tempéraments liés à l'anxiété. Une limitation dans la plupart de ces études est que les études sont de nature transversale et l'anxiété a été évaluée à un seul point dans le temps. De plus, seules quelques études ont été réalisées chez les enfants. Le but de la présente étude était d'étudier le rôle des gènes HTR2A et TPH2 dans le développement des trajectoires d’anxiété durant l’enfance. Les associations entre ces gènes, ces trajectoires, le diagnostic d’anxiété à l'âge adulte et les différences entre les sexes ont été examinées dans l'Étude Longitudinale des Enfants de Maternelle au Québec, composée de 3185 enfants recrutés en 1986-1987. Leur anxiété a été cotée par leur professeur annuellement entre 6 et 12 ans. Ces cotes ont été modélisées en trajectoires comportementales. Les données genotypées de 5-HT, disponibles pour 1068 personnes, ont été analysées en utilisant les statistiques du Chi-carré, des régressions logistiques et des analyses de variance. Sur les 37 polymorphismes étudiés, plusieurs ont été associés à la trajectoire de forte anxiété, tels le 5-HTR2A (rs1328684, rs95534511, rs1745837, rs7984966, 7330636) et TPH2 (rs11179050, rs11179052, rs1386498). Bien que les trajectoires d’anxiété en enfance n’aient pas prédit le diagnostic d'anxiété à 21 ans, les relations ont été trouvées entre ce diagnostic, HTR2A et les polymorphismes du nucléotide simple (PNS) de TPH2. On remarque que les PNS associés à l’anxiété durant l’enfance et l’âge adulte ne sont pas les mêmes. La force d'association entre les gènes étudiés et l'anxiété diffère entre les garçons et les filles. Cette étude est la première à identifier une association entre les variantes TPH2, 5-HTR2A et les trajectoires d’anxiété en enfance. Les études futures devraient reproduire les résultats dans d'autres échantillons, enquêter sur l'interaction avec les facteurs de stress, et étudier la pertinence fonctionnelle de la PNS. / A number of genes known to modulate serotonin (5-hydroxytryptamine, 5-HT) have been associated with anxiety-related temperaments. A limitation in most of these studies is that the studies are cross-sectional and anxiety has been measured at a single point in time. Furthermore, only a few studies have been done in children. The aim of the present study was to investigate the role of the HTR2A and TPH2 gene in the development of trajectories of anxiety in childhood/ adolescence. Associations between these genes, anxiety trajectories in childhood and anxiety diagnoses in adulthood were also investigated. Finally, gender differences were explored. Research questions were investigated in the Quebec Longitudinal Study of Kindergarten Children, consisting of 3185 boys and girls, selected in 1986-1987. Children`s anxiety was rated by their teacher every year between the age of 6 and 12 years. The ratings were modeled into behavioral trajectories. 5-HT genotyping data were available for 1068 cohort members. Data were analyzed using Chi-square statistics, logistic regressions and ANOVAs. Out of 37 investigated polymorphisms, several polymorphisms, such as 5-HTR2A (rs1328684, rs95534511, rs1745837, rs7984966, 7330636) and TPH2 (rs11179050, rs11179052, rs1386498) were associated with a high anxiety trajectory. Though trajectories of high anxiety in childhood did not predict an anxiety diagnosis at age 21, relationships were found between HTR2A and TPH2 SNPs and anxiety diagnosis at age 21. We note that the SNPs associated with anxiety were different between adults and children. The strength of association between the investigated genes and anxiety differed between boys and girls. This is the first study reporting an association with some HTR2A and TPH2 variants and trajectories of anxiety in children. Future studies should replicate the findings in other samples, investigate the interaction with stressors, and study the functional relevance of the SNPs

Deep brain stimulation (DBS) has emerged as a potential intervention for treatment-resistant tardive dyskinesia (TD). Despite promising case reports, no consensus exists regarding optimal stimulation parameters, neuroanatomical target for DBS in TD, or mechanisms underlying its anti-dyskinetic effects. We used vacuous chewing movements (VCMs) in rats treated chronically with haloperidol (HAL) as a TD model to address some of these issues. We show that acute DBS applied to the subthalamic nucleus (STN) or the entopeduncular nucleus (EPN) suppresses VCMs without affecting locomotor activity. Using immediate early gene mapping with zif268 as an index of neuronal activity, we found that STN-DBS induced decreases in activity throughout the basal ganglia, whereas EPN-DBS increased activity in projection regions. While chemical inactivation of the STN or EPN with the GABAA agonist muscimol also suppressed VCMs, muscimol infusion did not mimic the changes in neuronal activity induced by DBS, suggesting that DBS is not equivalent to functional inactivation. We next examined the contribution of serotonin (5-HT) and dopamine (DA) to the anti-dyskinetic effects of DBS. Decreasing 5-HT transmission pharmacologically or with serotonergic lesions decreased VCMs. Using microdialysis and zif268 mapping, we determined that STN- but not EPN-DBS decreased 5-HT release and activity of raphe neurons. However, when the decrease in 5-HT induced by STN-DBS was prevented by pre-treating rats with fluoxetine or fenfluramine, we found that decreasing 5-HT is not necessary for the anti-dyskinetic effects of DBS. STN-DBS transiently increased striatal DA release in intact rats only, whereas EPN-DBS had no effect on DA release. Moreover, pharmacologically elevating DA levels did not suppress VCMs. Together these findings lead us to conclude that increased DA release does not contribute to the anti-dyskinetic effects of DBS. Finally, we compared depressive- and anxiety-like behaviours induced by chronic DBS of the EPN and STN, since adverse psychiatric effects of DBS have become a significant clinical concern. STN-DBS but not EPN-DBS induced depressive-like behaviour in a learned helplessness task. We established that the chronic HAL VCM model preparation may be used to explore mechanisms underlying anti-dyskinetic and psychiatric effects of DBS, and provided the first investigations into these mechanisms.

Evidence suggests that selective serotonin reuptake inhibitors (SSRIs, a class of antidepressant medications) may contribute to increased breast cancer risk by stimulating the secretion of prolactin, a potential tumour promoter. The main objective of this study was to determine breast cancer risk associated with the duration, dosage and timing of SSRI use among women, with control for a limited set of confounders. This thesis project, conducted within the context of a population-based two-stage case-control study, consisted of a record linkage study utilizing three Saskatchewan health services databases. Cases included 1,273 women with primary breast cancer diagnosed between January 1, 2003 and December 31, 2005, and controls consisted of 12,730 subjects randomly selected from the province’s population registry. Data on SSRI use was compiled from the Saskatchewan prescription drug plan database. Information on a limited set of established risk factors for breast cancer that may confound this relationship was ascertained from the population registry and the prescription database. Cases and controls were similar in terms of age, total number of consecutive years eligible for prescription coverage and indicators of socioeconomic status. Compared to controls, cases were more likely to be married and to have used hormone therapy and/or oral contraceptives. Compared to nonusers, results indicated that the use of SSRIs for three or more years (as estimated by having filled 36 or more prescriptions for all SSRIs combined during the main exposure window more than two years prior to index date) was not associated with an increased risk of breast cancer (OR= 1.08, 95% CI: 0.74-1.58), controlling for age, marital status, oral contraceptive and hormone therapy use. In addition, no suggestion of increased risk was detected for long-term exposures to individual SSRIs (24 or more prescriptions filled during the main exposure window) and in relation to total combined SSRI use 2-7 years and more than seven years prior to index date. However, these risk estimates may have been affected by potential sources of information bias and confounding. In summary, these results do not provide evidence to suggest that the risk of breast cancer is increased with the use of SSRIs. / Thesis (Master, Community Health & Epidemiology) -- Queen's University, 2008-01-08 13:51:38.74

Serotonin receptor subtypes 5-HT1A, 5-HT2A and 5-HT2C are expressed in motoneurons and modulate motoneuron excitability. Serotonergic neurons, which increase their discharge with motor activity, make numerous contacts with motoneurons; however, little is known about the adaptability of motoneuron serotonin receptor expression in response to exercise. The purpose of this study was to determine the effect of a 7-day treadmill exercise protocol on 5-HT1A, 5-HT2A and 5-HT2C receptor mRNA levels in rat lumbar motoneurons. Lumbar motoneurons of exercised and sedentary animals were collected via laser capture microdissection. RNA was isolated from these samples and real-time reverse transcription polymerase chain reactions were performed to determine differences in receptor mRNA levels between exercised and sedentary animals. It appears that 5-HT1A, 5-HT2A and 5-HT2C receptor mRNA levels are unaltered following 7 days of treadmill exercise; however, future research must be done to determine if an exercise effect exists when motoneurons are differentiated by type.

Deep brain stimulation (DBS) has emerged as a potential intervention for treatment-resistant tardive dyskinesia (TD). Despite promising case reports, no consensus exists regarding optimal stimulation parameters, neuroanatomical target for DBS in TD, or mechanisms underlying its anti-dyskinetic effects. We used vacuous chewing movements (VCMs) in rats treated chronically with haloperidol (HAL) as a TD model to address some of these issues. We show that acute DBS applied to the subthalamic nucleus (STN) or the entopeduncular nucleus (EPN) suppresses VCMs without affecting locomotor activity. Using immediate early gene mapping with zif268 as an index of neuronal activity, we found that STN-DBS induced decreases in activity throughout the basal ganglia, whereas EPN-DBS increased activity in projection regions. While chemical inactivation of the STN or EPN with the GABAA agonist muscimol also suppressed VCMs, muscimol infusion did not mimic the changes in neuronal activity induced by DBS, suggesting that DBS is not equivalent to functional inactivation. We next examined the contribution of serotonin (5-HT) and dopamine (DA) to the anti-dyskinetic effects of DBS. Decreasing 5-HT transmission pharmacologically or with serotonergic lesions decreased VCMs. Using microdialysis and zif268 mapping, we determined that STN- but not EPN-DBS decreased 5-HT release and activity of raphe neurons. However, when the decrease in 5-HT induced by STN-DBS was prevented by pre-treating rats with fluoxetine or fenfluramine, we found that decreasing 5-HT is not necessary for the anti-dyskinetic effects of DBS. STN-DBS transiently increased striatal DA release in intact rats only, whereas EPN-DBS had no effect on DA release. Moreover, pharmacologically elevating DA levels did not suppress VCMs. Together these findings lead us to conclude that increased DA release does not contribute to the anti-dyskinetic effects of DBS. Finally, we compared depressive- and anxiety-like behaviours induced by chronic DBS of the EPN and STN, since adverse psychiatric effects of DBS have become a significant clinical concern. STN-DBS but not EPN-DBS induced depressive-like behaviour in a learned helplessness task. We established that the chronic HAL VCM model preparation may be used to explore mechanisms underlying anti-dyskinetic and psychiatric effects of DBS, and provided the first investigations into these mechanisms.

In the absence of ligand, certain growth factor receptors can be activated via G protein-coupled receptor (GPCR) activation in a process termed transactivation. Serotonin (5-HT) receptors can transactivate the receptor tyrosine kinase (RTK) platelet-derived growth factor (PDGF) ?? receptors in smooth muscle cells, but it is not known if similar pathways occur in neuronal cells. Here, it is shown that 5-HT can transiently increase the phosphorylation of PDGF?? receptors in a time- and concentration-dependent manner in SH-SY5Y neuroblastoma cells. This transactivation pathway was pertussis-toxin sensitive, and was dependent on phospholipase C activity, intracellular calcium signaling and subsequent protein kinase C activation. Exogenous application of non-lethal concentrations of H2O2 induced the phosphorylation of PDGF?? receptors in a concentration-dependent fashion, similar to that observed with 5-HT. Further investigation revealed reactive oxygen species (ROS) production as a necessary component in the transactivation pathway, as scavenging ROS eliminated PDGF?? receptor phosphorylation. NADPH oxidase was determined to be the likely source of ROS given that the NADPH oxidase inhibitors diphenyleneiodonium chloride and apocynin abrogated PDGF?? receptor transactivation. The role of Src tyrosine kinase was also investigated, and its location in this signaling cascade was determined to be downstream of calcium signaling, but upstream of NADPH oxidase activity. In addition, the activation of ERK1/2 in this system was elucidated to be independent of PDGF?? receptor transactivation. Interestingly, 5-HT also transactivated TrkB receptors, another RTK whose function is implicated in clinical depression. Expectedly, the enzymes in this mechanism were consistent with those revealed in 5-HT-to-PDGF?? receptor signaling. This cross-talk between 5-HT and RTKs such as TrkB and PDGF?? receptors identifies a potentially important signaling link between the serotonergic system and neurotrophic factor signaling in neurons that could have implications in mental health disorders including depression. Furthermore, although transactivation pathways are commonly initiated by a GPCR, recent reports have demonstrated that selective serotonin reuptake inhibitors (SSRIs) were able to block 5-HT-induced transactivation of PDGF?? receptors, suggesting that in addition to GPCRs, monoamine transporters may also be involved in RTK transactivation. SH-SY5Y cells pretreated with the SSRI fluoxetine blocked 5-HT-induced transactivation of the PDGF?? receptors, but not PDGF-induced PDGF?? receptor activation. Upon further examination, it was discovered that during the pretreatment period, fluoxetine itself was transiently transactivating the PDGF?? receptor via 5-HT2 receptors. By the end of the pretreatment period, the effects of fluoxetine on PDGF?? receptor phosphorylation had returned to baseline, and a subsequent transactivating stimulus (5-HT) failed to ???re-transactivate??? the PDGF?? receptor. Additional investigations demonstrated that 5-HT pretreatment can block dopamine-induced PDGF?? receptor transactivation, but not PDGF-induced PDGF?? receptor activation. This is the first demonstration of the heterologous desensitization of an RTK via a transactivation pathway, and this phenomenon is specific for transactivation pathways because in all cases the PDGF?? receptor ligand PDGF-BB was able to directly stimulate receptor activity in spite of GPCR agonist pretreatment. Heterologous desensitization in transactivation signaling reveals a previously unknown short-term ???blackout??? period wherein no further transactivation signaling can occur to potentially exploit the mitogenic effects of RTK activation.

Serotonin stimulates reproduction and inhibits feeding/growth in the neuroendocrine brain of goldfish. The objective of this thesis is to study the effects of selective serotonin reuptake inhibitor pharmaceuticals (SSRIs) on these systems, as SSRIs, such as fluoxetine, are detected in effluent and bioconcentrate in the brain of wild fish. Genes of the serotonin system were cloned to identify molecular conservation, seasonal expression, and tissue distribution. The serotonin transporter, the target molecule of fluoxetine, was highly conserved and ubiquitously expressed in goldfish. Seasonal changes of hypothalamic gene expression of the serotonin transporter support a role in the seasonal modulation of both processes. Fluoxetine injection experiments were used to assess effects on reproductive endpoints and to identify molecular mechanisms in the neuroendocrine brain. Fluoxetine inhibited serum estradiol concentrations in female goldfish and decreased isotocin mRNA abundance in the hypothalamus and telencephalon. Isotocin injections stimulated circulating estradiol concentrations, providing a causal link. Evidence for an involvement of serotonin in isotocin regulation was investigated using immunocytochemistry and 5-HT1A receptor agonists and antagonists. A close proximity of serotonin fibers and isotocin cell bodies and fibers was found in the telencephalon and pituitary,respectively. Injection of a 5-HT1A receptor antagonist inhibited isotocin mRNA expression in the telencephalon. Identified gene targets were investigated in waterborne fluoxetine exposures,including environmental concentrations. Waterborne fluoxetine led to a reduction in basal and pheromone-stimulated milt volume in male goldfish. Gene expression evidence indicated a central inhibitory effect of fluoxetine through the decrease in mRNA abundance of follicle-stimulating hormone in the pituitary and isotocin in the telencephalon. Feeding rate and weight decreased in fluoxetine-injected goldfish, indicating an anorexigenic effect. Fluoxetine induced changes in the gene expression of the feeding peptides neuropeptide Y, corticotropin-releasing factor, and cocaine- and amphetamine-regulated transcript-I in the hypothalamus and telencephalon. Waterborne exposure to fluoxetine validated the anorexigenic effect in goldfish and was correlated with increased expression of corticotropin-releasing factor mRNA, an anorectic peptide. The thesis provides evidence for disrupting effects of fluoxetine on neuroendocrine control of reproductive function and feeding/growth in goldfish, partially at environmental concentrations. The thesis provides the framework for the investigation of existing aquatic contaminants which modulate the serotonin system.