Fluoxetine, a selective serotonin re-uptake inhibitor (SSRI) and the active ingredient in Prozac®, is found in the environment and disrupts feeding and metabolism in exposed fish. The objective of this research was to investigate the mechanisms involved in the feeding and metabolism disruption in the model goldfish (Carassius auratus). Two short-term waterborne fluoxetine exposures (7- and 14-days) were performed using two environmentally relevant doses of fluoxetine (0.5 and 1 μg/L) and metabolic effects at the level of the brain, liver, serum and bile in goldfish were investigated. Abundances of mRNA transcripts coding for six feeding neuropeptides were examined to determine which may be involved in the initial neural changes associated with decreased appetite in goldfish. The 7-day fluoxetine exposure at 1 μg/L caused corticotropin-releasing factor (CRF) mRNA levels to increase by 2-fold in female hypothalamus and telencephalon, indicating that CRF may be one of the first of the feeding neuropeptides to be altered. Six hepatic miRNAs were also evaluated in the goldfish liver that were previously associated with fluoxetine exposure in zebrafish (Danio rerio). Following the 7-day exposure at 1 μg/L, miR-22b, miR-140, miR-210, miR-301a and miR-457b levels increased in the female goldfish liver by 4-6 fold. The 14-day fluoxetine exposure at 1 μg/L caused 2-fold increases in miR-210, miR-301a, miR-457b and let-7d in male goldfish liver. These miRNAs were associated with the down-regulation of anabolic metabolic pathways in zebrafish, indicating a conservation of miRNA and fluoxetine effect between fish species. Serum and bile metabolite profiles of fluoxetine exposed goldfish were evaluated using ultra performance liquid chromatography coupled to quadrupole time of flight mass spectrometry. Following the 14-day exposure at 1 μg/L, the bile metabolite profiles of male goldfish were significantly different from controls as detected by cluster analysis and fluoxetine was tentatively identified in the serum. No other discriminant metabolites were identified as of yet. The data presented suggest that fluoxetine causes metabolic disruption in goldfish at multiple organ levels. Because of the widespread detection of fluoxetine and other emerging SSRIs in the aquatic environment, future research is required to firmly establish this pharmaceutical class as a metabolic and endocrine disrupting chemical.

Animal personality can be defined as a set of physiological and behavioral characteristics that differ between individuals, but are consistent over time and across situations. The evolution of individual differences in behavior that are consistent over time and situations is still not clear. Our understanding of why animals have personality can be improved by investigating the underlying physiological mechanisms of animal behavior. Serotonin is a key monoamine that serves as a physiological modulator of animal behavior. Selective serotonin reuptake inhibitors are a group of chemicals that increase levels of serotonin in the brain. Fluoxetine is one such chemical and is used to treat depression in humans. In the field cricket (Gryllus bimaculatus), increased levels of serotonin have been linked to higher activity and boldness, which are both personality traits. In the current study, the effects of induced serotonin on activity, exploration, boldness and aggression was investigated. My results show that injecting fluoxetine causes substantial changes in behavioral traits used to describe personality in field crickets. This result is opposite to previous studies, as serotonin induced individuals were less active, less explorative, and won less fights, compared to control individuals. This could be due to serotonin existing naturally within the circulatory system of the field cricket, whereas fluoxetine is a manufactured chemical intended for human receptors, or that fluoxetine has a similar effect in modulating personality in field crickets as in humans. Since fluoxetine acts similarly in field crickets as in humans, an increased understanding of the effects of induced serotonin on different behaviors in field crickets could be beneficial for treating psychological illnesses.

To assess the long-term effects of antidepressant medication on balance, equilibrium, and postural reflexes, we studied 30 patients, ages 20-76 years, who had a diagnosis of depressive disorder (as defined by DSM-III-R criteria) and had been treated with tricyclic antidepressants (TCAs) or selective serotonin reuptake inhibitors (SSRIs) for ≤1 year. They were assessed by a Balance Master System. The assessment included three tasks: static balance, rhythmic weight shift, and limits of stability. When compared with 30 nonhospitalized healthy controls (of comparable age and the same sex), patients who took TCAs showed impaired balance function in all main indices. The results suggest that the impairment of balance function includes motor coordination, fine-motor control, postural reflexes,maintaining equilibrium, and reaction time. No obvious impairment of balance function was observed in patients who took SSRIs.

Die saure Sphingomyelinase (ASM) stellt durch die Umwandlung von Sphingomyelin in Ceramid und Phosphorylcholin ein zentrales, fein reguliertes Enzym im Sphingolipidmetabolismus dar. Dadurch nimmt es Einfluss auf verschiedene zelluläre Mechanismen wie Signalvermittlung, Endo- und Exozytose und Zellaktivierung. Dementsprechend weitreichend ist auch die Bedeutung der ASM bei verschiedenen Krankheiten wie Arteriosklerose, Depression oder Neoplasien. Auch auf das Immunsystem, insbesondere auf die Signalvermittlung durch T-Zellen innerhalb des adaptiven Immunsystems, nimmt die saure Sphingomyelinase Einfluss. Aufbauend auf früheren Forschungsarbeiten zur pharmakologischen und genetischen Hemmung der ASM im Mausmodell untersuchten wir, welche Auswirkungen die Hemmung dieses Enzyms in humanen Zellkulturen auf die Population regulatorischer und konventioneller T-Zellen haben. Hierzu verwendeten wir die beiden selektiven Serotonin-Wiederaufnahmehemmer Sertralin und Citalopram; zwei antidepressiv wirksame Medikamente, die durch eine Verdrängung der ASM von der lysosomalen Membran eine hemmende Wirkung ausüben. Wir konnten zeigen, dass diese beiden Substanzen sowohl in Maus-T-Zellen, als auch in humanen T-Zellen, in der Lage sind, die Aktivität der sauren Sphingomyelinase zu inhibieren. Durch Kultivierung von Immunzellen der Maus zusammen mit den Inhibitoren konnte darüber hinaus eine Erhöhung der Treg-Zellfrequenz erreicht werden. Verschiedene Zellkulturexperimente mit humanen PBMCs zeigten weiterhin, dass unter gewissen Umständen so auch eine Vermehrung regulatorischer T-Zellen im Menschen möglich ist, und dass dies mutmaßlich durch Einbindung der ASM im CD3/CD28-Signalweg bedingt ist. In mit AntiCD3-Antikörper stimulierten experimentellen Ansätzen kam es jedoch nur bei einzelnen Individuen, die als Responder identifiziert werden konnten, zu einer Treg-Zellvermehrung. Umgekehrt kam es durch externe Zugabe von C6-Ceramid zu einer Verringerung des Anteils an regulatorischen T-Zellen. Des Weiteren wurden verschiedene Veränderungen im Expressionsverhalten von Treg- und Tconv-Zellen bezüglich CD25, CD69 und CTLA-4 in Anwesenheit der ASMInhibitoren beobachtet. Weiterhin bestätigte sich, dass die pharmakologische Hemmung der sauren Sphingomyelinase auch Auswirkungen auf die Effektorfunktion von T-Zellen hat. Während die Proliferation der Zellen weitgehend unbeeinträchtigt blieb, kam es zu einer verringerten Sekretion der Zytokine IFN-gamma, TNF, IL-5 und IL-10. In ihrer Gesamtheit sprechen diese Ergebnisse dafür, dass Inhibitoren der sauren Sphingomyelinase begünstigend auf Krankheitsgeschehen mit überschießender oder dysregulierter Aktivität des Immunsystems einwirken könnten. Immunmodulatorischen Wirkungen durch Inhibition der ASM erklären möglicherweise auch Einflüsse auf das Immunsystem, die für verschiedene Antidepressiva beschrieben wurden. Insgesamt ist die Bedeutung der sauren Sphingomyelinase innerhalb der Regulation des adaptiven Immunsystems jedoch noch ein weitgehend ungeklärtes Thema mit vielen offenen Fragen. Daher ist auch in Zukunft weitere klinische und experimentelle Forschung erforderlich, um zu klären, welchen Einfluss dieses Enzyms auf Immunzellen hat und wie sich dieser auch klinisch anwenden lässt. / By catalyzing the transformation of sphingomyeline into ceramide and phosphocholine, the acid sphingomyelinase (ASM) plays a central role in the metabolism of sphingolipids and is tightly regulated. Therefore it takes essential influence upon different cellular mechanisms like signal transduction, endo-/exocytosis and cell activation. Accordingly complex is the importance of the ASM in different diseases like atherosclerosis, depression or neoplastic diseases. The acid sphingomyelinase also greatly influences the signal mediation of T cells within the adaptive immune system. Based on previous research about the pharmacological and genetic inhibition of the ASM in mice we investigated, which impact an inhibition of this enzyme in human cell cultures may have on the populations of regulatory and conventional T cells. Therefore we mostly used the two selective serotonin reuptake inhibitors sertraline and citalopram. These two antidepressive drugs detach the ASM from the lysosomal membrane and thereby inhibit the enzyme. Here we show, that these two substances efficiently inhibit the ASM mice T cells as well as human T cells. Cultivating immune cells of mice together with the inhibitors led to an essential increase in the frequency of regulatory T cells. Various cell culture experiments with human PBMCs showed that under certain circumstances an increase in regulatory T cells is also possible in the human, most likely due to the involvement of the ASM in the CD3/CD28 signal pathway. Experimental approaches using � CD3-antibodies showed an increase in Treg cells in a fraction of the tested individuals. External addition of C6-ceramide led to a decrease in the frequency of regulatory T cells. In addition to that, we were able to observe diverse effects regarding the expression of CD25, CD69 and CTLA-4 in Treg and Tconv cells in the presence of the ASM-inhibitors. We were also able to confirm that the pharmacological inhibition of the acid sphingomyelinase has an impact on the effector functions of T cells. While there was no effect on cell proliferation, we observed a decreased secretion of the cytokines IFN-gamma, TNF, IL-5 and IL-10. Alltogether these results indicate that inhibitors of the acid sphingomyelinase might have positive effects in pathologies of overshooting or dysregulated activity of the immune system. Immunomodulatory effects after inhibition of the ASM might also explain observations of an influence of antidepressants on the immune system that have been described in the literature. Overall the importance of the acid sphingomyelinase within the regulation of the adaptive immune system is a new field of research with many open questions. Therefore further clinical and experimental research is needed to clarify, which impact this enzyme has on immune cells and how this impact might be used therapeutically.

Depression is a common neuropsychiatric illness with a lifetime prevalence of 17% in the United States. The disease can severely impact the daily living and quality of life in patients. The monoamine hypothesis of depression implicates the neurotransmitter serotonin as mediating the pathophysiology. Selective serotonin reuptake inhibitors (SSRIs), a popular and efficacious class of antidepressants, increase serotonin concentrations in the brain. However, full clinical benefit may not be obtained for four to six weeks. This period of waiting for SSRIs to work becomes quite daunting for patients. Research has focused on delineating the control mechanisms surrounding the dorsal raphé nucleus (DRN), the serotonergic control center located in the midbrain. Much evidence points to changes in several receptor systems as the underlying cause of the delay. One particular serotonin receptor, 5-HT 1A , has been established to play a role in affecting the time course of clinical effect. We have targeted another receptor as a possible contributor to the delay: the stimulatory 5-HT 2A heteroreceptors located on GABAergic interneurons of the DRN. The 5-HT 2A receptors of the GABAergic interneurons receive stimulatory input from serotonergic collaterals branching off the DRN serotonergic neurons. The resultant stimulation causes GABA release and inhibition of the serotonergic neurons via GABA A receptors of the DRN, completing a feedback loop. We hypothesize that the 5-HT 2A receptors desensitize under constant stimulation, as in the case with SSRI administration, and as a result contribute to the time delay in the onset of action of SSRIs. Using the microdialysis technique, various receptor agonists and antagonists were administered to examine receptor changes and its influence on serotonin release in male Wistar rats. Our results demonstrate that GABA A receptors exert a large inhibitory influence on serotonergic neurotransmission. Local GABA release results from 5-HT 2A receptor stimulation. Furthermore, serotonin appears to trend back towards basal levels, suggesting a possible desensitization process occurring under constant agonism of 5-HT 2A receptors. The development of our pharmacodynamic model quantitatively shows a slow desensitization process, which may also contribute to the time delay observed with the onset of action of SSRIs.

Panic disorder (PD) is a debilitating anxiety disorder that often reduces the quality of life and some of its symptoms are physical distress and fear. PD is often comorbid with other anxiety disorders and depressive disorders and also cardiovascular and respiratory illnesses. Pharmacotherapy and psychotherapy are the two most common treatment options for people with PD. A standard type of pharmacotherapy is selective serotonin reuptake inhibitors (SSRI) which in short work by increasing the level of serotonin in the brain and has been shown to be efficacious and safe. A vital brain structure that is closely linked to PD is the amygdala, and some of its functions are learning, emotional processing, and memory. There seems to be a functional and structural abnormality in the amygdala for people with PD compared to healthy individuals, for example, a smaller volume of gray matter and increased activity. The aim of the thesis is to conduct a systematic review on the effect of SSRIs on the functional alterations of the amygdala in patients suffering from PD. The present systematic review will try to answer the question: If SSRIs affect amygdala activation for PD patients compared to healthy individuals who are currently not undergoing any kind of pharmacotherapy. The results showed opposite findings; one study did not detect activation changes in the amygdala for PD patients using SSRIs, one detected higher activity in the right amygdala, whereas the other two showed a decrease in the left amygdala (one study did not specify left, bilateral, or right). More research regarding amygdala activation in PD patients using SSRIs is needed due to the small scale of studies currently available.

No description available.

Approximately 10% of pregnant women take antidepressants. Prenatal exposure to selective serotonin reuptake inhibitors (SSRIs), a class of antidepressants, has been shown to alter serotonergic signaling in the brain. However, the effects of SSRIs on peripheral serotonin (5HT) synthesis and/or signaling have largely been ignored. Serotonin in the gut is critical for intestinal function and dysregulation of this pathway is associated with intestinal disease. Therefore, the goal of this study was to determine the effects of perinatal exposure to the SSRI fluoxetine (Prozac®) on intestinal health in the offspring. Dams were given vehicle or fluoxetine hydrochloride (FLX 10 mg/kg/d; N=15) for 2 weeks prior to mating until weaning. We assessed markers of serotonergic signaling, inflammation, and composition of the gut microbiota in the offspring. Male offspring of fluoxetine-treated dams had significantly elevated serum levels of 5-HT and decreased expression of the 5HT2A receptor and MAO. In female offspring there was no effect of SSRI exposure to alter any components of serotonergic signaling. Although we did not find any evidence of increased inflammation following fluoxetine exposure, there were significant alterations in the composition of the gut microbiota in the exposed offspring. Male offspring of SSRIs-exposed mothers had changes in key components of the gut serotonergic system in association with elevated levels of serum 5-HT and alterations in the gut microbiota in adulthood. The impact of these changes on intestinal health and the reasons for the sex specific effects remain to be determined. / Thesis / Master of Science in Medical Sciences (MSMS)

10-15% of women take antidepressants during pregnancy. Selective serotonin reuptake inhibitors (SSRIs) are most commonly used for perinatal depression. Perinatal exposure to SSRIs has been shown to disrupt the development of serotonergic signaling pathways in the central nervous system (CNS); however, the effects on the developing enteric nervous system (ENS) remain relatively unexplored. We hypothesized that early life exposure to SSRIs would influence the structural development of the gastrointestinal (GI) tract. We further hypothesized that these structural changes could lead to clinically relevant functional outcomes, such as modifications in susceptibility to inflammation and altered GI motility. Female Wistar rats were given the SSRI, fluoxetine, or vehicle from 2 weeks prior to mating through gestation until weaning. At postnatal day 1 (P1), postnatal day 21 (P21; weaning) and 6 months of age (P6 months) intestines were harvested to assess for structural changes. At P6M, intestines were collected to assess motility in vitro and subsets of the offspring were treated with dextran sulfate sodium (DSS) to assess susceptibility to colitis. At P1, there was a significant decrease in serotonergic neurons in the female colon. At P21, there was a significant increase in serotonergic neurons of both sexes in the colon. At P6M, there was a significant increase in the frequency and velocity of long-distance contractions in the colon when both sexes were combined and an increase in ZO-1 in male colon. In conclusion, SSRI exposure in utero appears to have structural and functional consequences on the developing ENS in the SSRI exposed offspring. The structural consequences are seen in both sexes at P21 and although the structural changes to the ENS resolve by 6 months, motility in the colon continues to be significantly altered. There were no significant differences in chemical colitis, however, we did see difference of quantitative mRNA cytokines, chemokines and extracellular matrix components which may suggest differences in mucosal immune response. The mechanisms by which these changes occur remain to be explored. / Thesis / Master of Science (MSc)

Selective Serotonin Reuptake Inhibitors (SSRIs) are the most frequently prescribed class of drugs worldwide and are implemented in the treatment of depression and other psychiatric disorders. SSRIs relieve depressive symptoms by modulating levels of the neurotransmitter serotonin in the brain. SSRIs block the function of the serotonin transporter, thereby increasing concentrations of extracellular serotonin. However, serotonin levels in the neurons of the brain only account for 5% while the remaining 95% is present outside the brain. Serotonin receptors and transporter are located on bone resident cells (mesenchymal stem cells (MSCs)), osteoblasts and osteoclasts, and serotonergic activity is believed to affect bone homeostasis. Consequently, alterations in serotonin levels by SSRI treatment have the potential to alter bone formation and remodeling. Clinical reports correlate increase risk of bone fractures and delayed bone healing with SSRI use. Metallic implants are commonly used as orthopedic and dental implants to fix bony defects. Surface modifications have been used to increase the level of bone to implant contact by controlling the differentiation of MSCs into an osteoblastic linage and facilitate bone production. However, it is not known if SSRIs can affect MSCs osteoblastic differentiation and bone remodeling signaling in response to microstructured biomaterials. The aims of this study were: 1) Investigate the effects of SSRIs on MSCs differentiation on microstructured titanium (Ti), 2) Determine the effects of SSRIs on bone remodeling signaling and osteoclast activation, and 3) Elucidate the effects of SSRIs on serotonin receptors and their effect on bone remodeling. To investigate this, human MSCs were grown on tissue culture polystyrene (TCPS), smooth Ti (PT) or microstructured Ti (SLA) surfaces under exposure to therapeutic concentrations of commonly prescribed antidepressants (SSRIs (fluoxetine, sertraline, paroxetine), Selective Norepinephrine Reuptake Inhibitor (SNRI) (duloxetine) and other regularly prescribed antidepressants (bupropion)) during differentiation toward osteoblasts. Osteoblastic differentiation was assessed in MSCs after treatment with the drugs (0.1μM, 1μM, 10μM) by alkaline phosphatase activity and osteocalcin levels. Antidepressant treatment decreased levels of MSC differentiation markers on microstructured Ti surfaces. Furthermore, treatment dose-dependently decreased protein levels secreted by MSCs which are important for bone formation (BMP2, VEGF, Osteoprotegerin), and increased those involved in bone resorption (RANKL). To determine the effect of SSRIs on bone remodeling signaling and osteoclast activation, human osteoclasts were either directly exposed to antidepressants or conditioned media obtained from MSCs treated with antidepressants on Ti surfaces, after which, enzymatic tartrate-resistant acid phosphatase (TRAP) activity was assessed. Antidepressants increased TRAP activity both directly and through treated MSCs, with the highest levels evident after treatment with conditioned media from MSCs on microstructured Ti surfaces. To elucidate the effects of serotonin receptors and their effect on bone remodeling, receptors were pharmacologically inhibited. Surface roughness decreased gene expression of HTR2A, HTR1B, and HTR2B, and antidepressant treatment increased their expression. Inhibition of HTR2A decreased RANKL protein levels, while inhibition of other serotonin receptors had no effect on RANKL or OPG levels. These studies suggest that antidepressants inhibit MSCs differentiation on microstructured Ti surfaces and increase levels of proteins associated with bone resorption. Additionally, our results showed that RANKL is regulated by serotonin receptor HTR2A. Taken together, our results suggest that antidepressants have a negative effect on osteoblastic differentiation, compromising bone formation and enhancing bone resorption, which can be detrimental to patients under orthopedic and dental treatment.