Thesis (M.S.)--University of North Carolina Wilmington, 2007. / Includes bibliographical references (leaves: 67-68)

Selective serotonin (5-HT) reuptake inhibitors (SSRIs) particularly fluoxetine (FLX, Prozac®), are often the first-line of pharmacological treatment for affective disorders in pregnant women. Given that SSRIs readily cross the placenta, a fetus from a SSRI-treated pregnant woman is potentially at risk from the disruptive effects of the SSRIs-induced 5-HT actions during this highly plastic stage of development. One of the prominent roles of 5-HT that we will explore here is its involvement in the development and programming of the stress axis. Pharmaceuticals including FLX and other SSRIs reach aquatic ecosystems through sewage release, so fish may also be inadvertently exposed. We investigated the premise that early-life exposure to FLX induces a transgenerational disruption of the stress axis using the zebrafish (ZF) Danio rerio, as a research model to encompass both the environmental and human health concerns. The FLX concentrations studied were environmentally relevant (0.54 µg·L-1) or comparable to concentrations detected in the cord blood of FLX-treated pregnant women (54 µg·L-1). Exposure to FLX during the first 6 days of life induced a reduction of whole-body cortisol levels in adult ZF (filial generation 0; F0), an effect that persisted across 4 consecutive generations without diminution, even though the descendants (F1 to F4) were not directly exposed to FLX. This effect was more pronounced and persistent in males than females. The in vivo cortisol response of the interrenal cells (the fish ‘adrenal’) to an intraperitoneal injection of adrenocorticotropic hormone was also reduced in the F0 and F3 FLX-exposed males. RNA sequencing of the F0 and F3 male whole kidney containing the interrenal cells detected an array of differentially expressed genes (>500) altered by FLX treatment. Enrichment analysis of these genes revealed that early FLX exposure significantly modified numerous canonical pathways (>40) including key pathways related to steroidogenesis. These findings provide further insights on the underlying mechanism of the transgenerational disruption induced by FLX. We also showed that altered cortisol levels were linked to reduced exploratory behavior in adult males from the F0 to F2 FLX lineage. In contrast, females were susceptible to the effects of FLX-induced hypocortisolism during a different window of development. Exposure to FLX in the sex differentiation period (15 to 42 days post-fertilization) increased exploratory behavior in the adult females. Transcriptional profile of selected steroidogenic genes in the whole-larvae from the F0 varied in magnitude and direction in both treatments, despite the same low cortisol phenotype induced by both concentrations. We also found an up-regulation in the transcript levels of steroidogenic-related genes and a down-regulation of a gene involved in the inactivation of cortisol in the F3 larvae ancestrally exposed to the human-relevant concentration. These findings on the transcript levels of the selected genes in the larvae from F0 and F3 suggest that the larvae adopted specific coping mechanism(s) to the disruptive effects of FLX depending on the exposure concentration and the filial generation. The pigmentation patterns in some of the descendants of the exposed fish (F1 to F3) were reduced by the 6-day early-FLX treatment. In response to a 6-day embryonic exposure to a second antidepressant, venlafaxine, the F4 adult females that were ancestrally exposed (in the F0) to the human-relevant FLX concentration displayed an intensified reduction of cortisol levels. Therefore, FLX exposure of the great-great-grandparents (F0) permanently and most likely epigenetically shaped the response of future generations to other antidepressants. Collectively, our data are cause for concern, given the high-prescription rates of FLX to pregnant women and the potential long-term negative impacts on humans and aquatic organisms exposed to ever rising levels of SSRIs.

According to the literature, there is a decrease in glial cell number or hypofunction of glial cells in depression. It was also found that both antidepressants and atypical antipsychotics might target glial cells, and that they increase the release of glial-cell-line-derived neurotrophic factor (GDNF) from C6 rat glioma cells (C6 cells). In this project, C6 cells were used as a model for glial cells to investigate the effects of fluoxetine and quetiapine on proliferation and differentiation, and to investigate their effects on the release of GDNF. A combination of quetiapine and fluoxetine was used to study their potential synergistic effect on the release of GDNF from C6 cells. <p>C6 cells were treated with different concentrations of fluoxetine and quetiapine in both normal and serum starvation culture conditions. Under the serum present condition, fluoxetine (25 mM) decreased the number of C6 cells from 24 to 48 h, while quetiapine (25 mM) decreased the cell number only at 48h. Under serum starvation, it was found that fluoxetine (12.5 mM) increased the number of C6 cells from 24 to 48 h treatment; in contrast, quetiapine (25 mM) decreased the number of C6 cells after 48 h treatment. Both fluoxetine and quetiapine inhibited the proliferation of C6 cells under normal and serum starvation conditions. Fluoxetine (12.5 mM) decreased C6 cell death, while quetiapine had no significant effect. Fluoxetine, but not quetiapine, changed the morphology of C6 cells and increased the level of glial fibrillary acidic protein (GFAP), an astrocyte marker. Both fluoxetine (12.5, 25 mM) and quetiapine (25 mM) increased the release of GDNF from C6 cells, and an apparent additive effect was found between quetiapine and fluoxetine in the modulation of release of GDNF from these cells. <p>It was concluded that:<p>1. High concentration (25 mM) of fluoxetine and quetiapine decreased the number of C6 cells under the serum present condition and both drugs inhibited the proliferation of C6 cells.<p>2. Fluoxetine had a protective effect on the C6 cells under serum starvation, and affected the differentiation of C6 cells; this implies that fluoxetine may protect glial cells in vivo and affect their differentiation. <p>3. A high concentration of quetiapine decreased the number of C6 cells and inhibited the proliferation under serum starvation; even though it increased the release of GDNF from C6 cells as did fluoxetine.<p>4. Both quetiapine and fluoxetine increased the release of GDNF from <p>C6 cells under serum starvation. The combination of quetiapine and fluoxetine had an apparent additive effect in the modulation of GDNF release.<p>5. These effects on proliferation & GDNF release may underlie the benefit observed with these drugs in treating depression and schizophrenia.

According to the literature, there is a decrease in glial cell number or hypofunction of glial cells in depression. It was also found that both antidepressants and atypical antipsychotics might target glial cells, and that they increase the release of glial-cell-line-derived neurotrophic factor (GDNF) from C6 rat glioma cells (C6 cells). In this project, C6 cells were used as a model for glial cells to investigate the effects of fluoxetine and quetiapine on proliferation and differentiation, and to investigate their effects on the release of GDNF. A combination of quetiapine and fluoxetine was used to study their potential synergistic effect on the release of GDNF from C6 cells. <p>C6 cells were treated with different concentrations of fluoxetine and quetiapine in both normal and serum starvation culture conditions. Under the serum present condition, fluoxetine (25 mM) decreased the number of C6 cells from 24 to 48 h, while quetiapine (25 mM) decreased the cell number only at 48h. Under serum starvation, it was found that fluoxetine (12.5 mM) increased the number of C6 cells from 24 to 48 h treatment; in contrast, quetiapine (25 mM) decreased the number of C6 cells after 48 h treatment. Both fluoxetine and quetiapine inhibited the proliferation of C6 cells under normal and serum starvation conditions. Fluoxetine (12.5 mM) decreased C6 cell death, while quetiapine had no significant effect. Fluoxetine, but not quetiapine, changed the morphology of C6 cells and increased the level of glial fibrillary acidic protein (GFAP), an astrocyte marker. Both fluoxetine (12.5, 25 mM) and quetiapine (25 mM) increased the release of GDNF from C6 cells, and an apparent additive effect was found between quetiapine and fluoxetine in the modulation of release of GDNF from these cells. <p>It was concluded that:<p>1. High concentration (25 mM) of fluoxetine and quetiapine decreased the number of C6 cells under the serum present condition and both drugs inhibited the proliferation of C6 cells.<p>2. Fluoxetine had a protective effect on the C6 cells under serum starvation, and affected the differentiation of C6 cells; this implies that fluoxetine may protect glial cells in vivo and affect their differentiation. <p>3. A high concentration of quetiapine decreased the number of C6 cells and inhibited the proliferation under serum starvation; even though it increased the release of GDNF from C6 cells as did fluoxetine.<p>4. Both quetiapine and fluoxetine increased the release of GDNF from <p>C6 cells under serum starvation. The combination of quetiapine and fluoxetine had an apparent additive effect in the modulation of GDNF release.<p>5. These effects on proliferation & GDNF release may underlie the benefit observed with these drugs in treating depression and schizophrenia.

Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (leaves 100-120).

Thesis (Ph. D.)-- Florida State University, 2006. / Advisor: Cathy W. Levenson, Florida State University, College of Human Sciences, Dept. of Nutrition, Food, and Exercise Science. Title and description from dissertation home page (viewed Jan. 2, 2007). Document formatted into pages; contains xi, 83 pages. Includes bibliographical references.

Anti-depressants are commonly used to treat major depression and post-traumatic stress disorder. 17% of women experience major depression during pregnancy, where up to 10% of pregnant women use antidepressants. 20% these women use Prozac (fluoxetine) to treat major depressive symptoms, which crosses the placental barrier and is present in breast milk. Little is known about how exposure to developmental fluoxetine affects adulthood behaviors such as agonistic and submissive behaviors, especially in females. Furthermore, the effects of developmental fluoxetine exposure on aggression and avoidance in Syrian hamsters have not been studied. Therefore, we explored how prenatal and perinatal exposure to fluoxetine affects adulthood aggression and avoidance in male and female Syrian hamsters. Dams were given fluoxetine via drinking water 7 days prior impregnation. Fluoxetine administration continue until offspring reached postnatal day (PD) 12. The offspring were weaned and group-housed at PD 25 and single-housed at PD 60. Animals were handled one week prior to behavioral testing. The following week, animals were tested for aggression in a neutral arena with a non-aggressive stimulus hamster of the same sex. Another group of hamsters were tested for avoidance behavior in a neutral arena 24 hours after social defeat. Duration of aggression and avoidance were quantified. There was no main effect of sex or drug nor was there an interaction. Therefore, we reject our hypothesis of prenatal and perinatal exposure to fluoxetine will affect aggression and avoidance in male and female Syrian hamsters. These findings may be due to a ceiling effect in Syrian hamsters, where the subtle effects of developmental fluoxetine exposure were not observable.

Depression is a complex psychiatric illness that affects a large proportion of the population. Many researchers make use of preclinical animal models to study the behavioural and neurobiological characteristics of this disease. However, although a bias towards maladaptive thinking patterns and emotional responses is a cardinal symptom of depression, these symptoms have been rarely considered in preclinical models. One way to investigate maladaptive thinking is through the use of fear conditioning paradigms. Fear conditioning evaluates emotional memory by assessing a rodent’s ability to associate neutral cues with an aversive experience. It requires the activation of brain structures critically involved in emotion-related learning and memory processes, most notably the hippocampus and amygdala, to successfully learn the task. The primary goal of this dissertation was to gain a better understanding of the consequences of repeated corticosterone injections—a validated preclinical model of depression-- on emotionally driven behaviour, the involvement of the hippocampus and amygdala in mediating these behaviours, and whether the antidepressant, fluoxetine, can prevent the effects of corticosterone on these behaviours. To begin, in Chapter 2 I confirmed that the depressogenic effects of corticosterone in the forced swim test, which is a traditional behavioural assay for depression in rodents, are not due to procedural differences or non-specific motor effects. I then investigated the impact of repeated corticosterone injections on the learning and memory of delay and contextual fear conditioning. I examined whether altering the order in which rats recall context versus tone cued fear associations determines the magnitude of corticosterone’s effect on conditioned fear. I found that corticosterone dose-dependently increased freezing to contextual cues whereas freezing to tone cues was increased regardless of dose. Furthermore, the order of the presentation of context versus tone cues during recall determined whether corticosterone produced significant enhancements in freezing. In Chapter 4, I investigated whether neuronal activity in the hippocampus and amygdala after recall of contextual or tone cued fear was associated with the effects of corticosterone found in Chapter 3. Recall of contextual cues was associated with neuronal activity in specific sub regions of the amygdala without any observed changes in the hippocampus. In Chapter 5, I investigated whether repeated corticosterone injections would also enhance the learning and memory of trace fear conditioning, a task that is heavily reliant on the hippocampus. I found that corticosterone increased freezing during recall of trace cues and enhanced the acquisition of trace cues. The results from this chapter, taken together with the results from chapters 3 and 4, suggest that repeated corticosterone exposure readily enhances learning and memory processes that evoke emotional arousal. In Chapter 6, I asked whether repeated treatment with the antidepressant, fluoxetine, could prevent increased fear learning produced by repeated corticosterone injections. I found that fluoxetine decreased freezing behaviour in corticosterone rats during recall of tone cues. Overall, the results of this dissertation further our understanding of the effects of corticosterone on learning and memory tasks that evoke emotional arousal, support the use of fear conditioning as a measure of depression-like behaviour, and demonstrate that repeated corticosterone injections reliably produce a depressive phenotype in rats.

Syrian hamsters are a useful model for offensive aggression because males and females spontaneously engage in agonistic bouts. In hamsters, there is a large sex difference on aggression in the serotonin (5-HT) pathways. Male aggression is inhibited and female aggression increases with injections of a 5-HT agonist into the anterior hypothalamus (AH), but little is known if similar effects are seen in adult hamsters with repeated systemic administration of the selective serotonin reuptake inhibitor (SSRI), fluoxetine (FLX), which is one of the few approved pharmacological treatments for mood disorders in children and adolescents. The goal of this study is to determine if repeated intraperitoneal injections of FLX over 30 days in adolescent male and female hamsters has an effect on offensive aggression similar to site specific alterations of the 5-HT system in the AH. Our data suggest that systemic administration of FLX as adolescents over 30 days does not affect offensive aggression in males or females as adults.

In male golden hamsters, puberty is marked by dramatic changes in agonistic behavior. Attack frequency gradually decreases as agonistic behavior evolves from play fighting to adult aggression. Attack types change as targets of attack mature from play fighting to adult attacks. In adult hamsters, serotonin plays an inhibitory role in aggression. Thus, the decline in attack frequency during puberty could be associated with an up-regulation of the activity of the serotonergic system. In adults, acute Fluoxetine treatment inhibited aggressive behavior at all doses. In juveniles, only the highest dose reduced attack frequency. Interestingly, juveniles treated with the lowest dose showed an increase in aggressive behavior. Attack type was also affected as treatment with Fluoxetine accelerated the maturation of attack targets. This same effect had been observed in previous studies in response to chronic social stress and dexamethasone treatment. Consequently, the role of cortisol on the development of the serotonergic system was also investigated. Furthermore, the density of serotonin innervation in the anterior hypothalamus and medial amygdala was found to be higher in adults than juveniles and consistent with the inhibition of attacks by the high dose of Fluoxetine. However, the differential effects of Fluoxetine at the lower doses were investigated through analysis of different serotonin receptor subtypes. In adult hamsters, aggression can be facilitated by activation of 5-HT₃ receptors and inhibited by 5-HT[subscript 1A] receptors. During puberty, the density of immunoreactive 5-HT1A receptors increased in the anterior hypothalamus and medial amydala while 5-HT₃ receptor immunoreactivity did not change. Thus, it is possible that in these areas the ratio of 5-HT₃ to 5-HT[subscript 1A] receptors decreases during puberty. This change is consistent with the decline in the frequency of offensive responses during puberty. The functionality of 5-HT[subscript 1A] and 5-HT₃ receptors on offensive aggression in juveniles was tested via peripheral injections of a 5-HT[subscript 1A] receptor agonist and a 5-HT₃ receptors antagonist. At the high dose, both drug treatments inhibited attack frequency and attack repetition. Together, these data examine the role of the serotonergic system on the development of agonistic behavior. / text