No description available.

No description available.

<p>Several classes of psychotropic medications are known to produce neurological side effects. It has long been recognized that antipsychotic drugs classically block the D₂ subtype of DA receptors inducing a range of acute and subacute extrapyramidal syndromes (EPS), including parkinsonism and akathisia, as well as chronic syndromes such as tardive dyskinesia. More recently, SSRI-type drugs, which, as the name suggests, inhibit the serotonin transporter (SERT), and have been found to induce a similar profile of EPS. It is unclear how medications with such different pharmacological actions can produce similar neurological side effects. The goal of this thesis was to study the neurochemical alterations induced by antipsychotic and SSRI medications, with a specific focus on the nigrostriatal pathway, the causative location of parkinsonism.</p> <p>Environmental enrichment and exercise (EE) has been shown to have protective effects in various neurological settings. In the first experiment, we studied the changes induced by SERT inhibition compared to those induced by a non-pharmacological form of therapy, namely, environmental enrichment with exercise. The SSRI, fluoxetine (FLX) significantly reduced the levels of tyrosine hydroxylase (TH) and phosphorylated glycogen synthase kinase-3β (pGSK-3β-inactive), while increasing phosphorylated TH (pTH) in the striatum (STR). EE also reduced TH and increased pTH, but contrary to FLX, it significantly increased striatal pGSK-3β protein expression.</p> <p>Microglia, the brain’s primary immune cells, have been implicated in several neuroinflammatory conditions, including Parkinson’s disease. The purpose of the second experiment was to explore the modulatory effects of microglia on neuroleptic-induced changes in the nigrostriatal system. The typical antipsychotic, haloperidol (HAL), did not affect the overall levels of TH, though it did induce a robust increase in pTH. The microglial NADPH oxidase inhibitor, apocynin (APO), significantly attenuated this increase in pTH. HAL also induced a significant increase in striatal pGSK-3β, while apocynin, rather surprisingly, induced a stark decrease in pGSK-3β protein expression.</p> <p>The results of this thesis indicate that both pTH and pGSK-3β are intriguing markers to study in the context of dopamine neurotransmission. In addition, EE proved to be a valuable modality in which to compare the downstream effects of pharmacological treatment. It is also clear that microglia fulfill an undefined, but fascinating role as modulators of neural transmission.</p> / Master of Science in Medical Sciences (MSMS)

Introduction: The role of short-chain fatty acids (SCFAs) in colonic motility is controversial. Germ free (GF) mice are unable to produce SCFAs and serve as a model to study how their absence affects colonic motility. GF transit is slower than controls and colonization of these mice improves gastrointestinal (GI) transit and serotonin (5-HT) levels. Our aim was to determine the role SCFAs play in improving transit, and whether this is dependent on mucosal 5-HT signaling. Methods: Motility was assessed in GF mice via spatiotemporal mapping with intraluminal perfusion of either PBS or SCFA cocktail. Outflow from the colon was recorded to quantify propulsive contractions. Motility was then assessed in TPH1-KO mice with PBS, butyrate and then propionate. GPR43 and 5-HT staining was performed in control and GF colons. Mice were then given chow diet or high sugar diet (HSD) and motility was recorded. Fecal pellets were taken at baseline and just prior to motility experiments and SCFA levels were measured with mass spectrometry. Results: GF mice exhibit significantly lower proportion of propulsive contractions, lower volume of outflow per contraction and slower velocity of contractions compared to controls. SCFAs changed the motility patterns to that of the controls in all parameters. Butyrate administration significantly increased the proportion of propulsive contractions in controls, yet failed to in TPH1 KO mice. Propionate significantly inhibited propulsive contractions in both mice. HSD-fed mice were not different from chow-fed mice in any parameter. No SCFA was significantly reduced, but the change in butyrate concentration was significantly associated with LDC frequency. Conclusions: Our results reveal significant abnormalities in the propulsive nature of colon motor patterns in GF mice, explaining the decreased transit time in in vivo studies. We show that butyrate, not propionate, activates propulsive motility and that this requires mucosal 5-HT, possibly released by ECs. / Thesis / Master of Science (MSc)

Breast cancer therapy resistance and disease recurrence are driven by an infrequent population of stem-like tumor cells, termed breast cancer stem cells or tumor-initiating cells (BTIC). Whereas drugs that target BTIC could be combined with conventional therapies to provide durable remissions, identifying such agents has been difficult. To achieve the latter, our lab screened more than 35,000 compounds for their capacity to reduce the activity of BTIC-enriched mouse mammary tumorspheres, wherein we identified numerous antagonists of multiple serotonin receptors (HTRs). The serotonergic antagonist that prevented sphere formation with the highest potency is a highly selective antagonist of HTR5A, SB-699551. We subsequently demonstrated that this agent affects BTIC activity in breast tumor cell lines representative of all clinical and molecular subtypes of breast cancer. Whereas the primary target of SB-699551 is known, the downstream signaling pathways responsible for its anti-BTIC effect remains enigmatic. The goal of this thesis work was to elucidate the signaling pathways downstream of HTR5A in human breast tumor cell lines. We used a phospho-proteomic approach to establish that treatment of human SB-699551 affects the phosphorylation of proteins involved in the Gi-coupled and the PI3K/AKT/mTOR signaling axes. Moreover, we demonstrated that selective antagonists of PI3K, AKT, and mTOR phenocopied the effect of SB-699551 in tumorsphere forming assays. Taken together, our data suggests that SB-699551 elicits its effect through the PI3K/AKT/mTOR signaling pathways downstream of HTR5A. / Thesis / Master of Health Sciences (MSc) / Accumulating data suggests that the progression of breast cancer is driven by a rare population of breast tumor-initiating cells (BTIC). BTIC lie dormant during conventional therapy and initiate recurrence after such therapies are withdrawn. Hence, there is an urgent need to develop drugs that target BTIC that can be combined with the current standard of care to improve the durability of remission. With the latter objective in mind, our lab previously determined that antagonists of serotonin signaling target BTIC. One of the agents that we identified in our screen inhibits the activity of serotonin receptor 5A (HTR5A). The exact signaling mechanism whereby inhibition of HTR5A leads to a loss in BTIC activity was enigmatic. Hence, this thesis aims to elucidate the signaling pathways downstream of HTR5A in breast cancer. Knowledge of the latter will help identify a plausible mechanism in addition to identifying biomarkers of therapy efficacy.

No description available.

This study examined the relationship between selective serotonin reuptake inhibitor (SSRI) medication and auditory measures in clinically depressed women. Experimental subjects were tested in both a medicated and unmedicated condition. Experimental subjects were compared to a normal control group; additionally intrasubject comparison was made within the experimental group. Test measures included: audiometry, tympanometry, otoacoustic emissions, uncomfortable loudness level, masking level difference, SCAN-A, Synthetic Sentence Identification (SSI), and the low predictability section of the Revised Speech in noise (RSPIN). The unmedicated group scored significantly less favorably than the control group on the following tests; SCAN-A (composite, filtered words, and auditory figure ground), R-SPIN (0MCR condition in both the right and left ears). Additionally, the unmedicated group scored significantly less favorably than the medicated group on the SSI (-20MCR condition right ear only) and of the R-SPIN (0MCR condition right ear only). Other test measures indicated consistent trends but did reach significance.

Schizophrenia is a chronic psychotic illness affecting ~21 million people globally. Currently available antipsychotic agents act through a dopamine D2 receptor mechanism, and produce extrapyramidal or metabolic side effects. Hence, there is a need for novel targets and agents. The mGlu2/5-HT2A receptor heteromer has been implicated in the action of antipsychotic agents, and represents a novel and attractive therapeutic target for the treatment of schizophrenia. A long-term goal of this project is to synthesize bivalent ligands where a 5-HT2A receptor antagonist is tethered to an mGlu2 PAM via a linker. The goals of the investigation were to study the SAR of risperidone (an atypical antipsychotic agent) at 5-HT2A receptors using a “deconstruction-reconstruction-elaboration” approach to determine the minimal structural features of risperidone that contribute to its 5-HT2A receptor affinity and antagonism, and to determine where on the “minimized risperidone” structure an mGlu2 PAM can be introduced. Additional goals included studying the binding modes of various mGlu2 PAMs and identifying where on an mGlu2 PAM a risperidone “partial” structure could be introduced. Biological studies of deconstructed/elaborated analogs of risperidone suggest that the entire structure of risperidone is not necessary for 5-HT2A receptor affinity and antagonism, and that a fluoro group contributes to 5-HT2A binding. 6-Fluoro-3-(4-piperidinyl)-1,2-benz[d]isoxazole that has only half the structural features of risperidone retains 5-HT2A receptor affinity and antagonist activity, and represents the “minimized risperidone” structure with the piperidine nitrogen atom representing a potential linker site for eventual construction of bivalent ligands. Molecular modeling studies at 5-HT2A receptors suggest that risperidone and its analogs have more than one binding mode. Modeling studies to evaluate binding modes of various PAMs at mGlu2 receptors, coupled with known SAR information, were used to identify a PAM (JNJ-40411813), and the pyridone nitrogen atom of JNJ-40411813 as a potential linker site. Additionally, potential synthetic routes for JNJ-40411813 were explored that might be of value in the synthesis of bivalent ligands. Based on the structural features of 6-fluoro-3-(4-piperidinyl)-1,2-benz[d]isoxazole, a new pharmacophore for 5-HT2A receptor antagonists, consisting of one aromatic region, a basic protonated amine and hydrogen bond acceptors, has been proposed.

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.

INTRODUÇÃO: Apesar dos Inibidores Seletivos da Recaptura da Serotonina (ISRSs) serem a primeira escolha no tratamento do Transtorno de Estresse Pós-Traumático (TEPT) seu mecanismo de ação não é completamente compreendido. Possivelmente, um aumento na resiliência ao estresse esteja envolvido. Como a serotonina (5HT) ajuda a mediar as respostas ao estresse em outros transtornos ansiosos, o paradigma de Depleção de Triptofano Aguda (DTa) foi usado para diminuir a 5HT central em Pacientes com TEPT remitido com ISRSs. MÉTODOS: Dez pacientes com TEPT (diagnosticados pela Mini Entrevista Neuropsiquiátrica Internacional) que tiveram resposta completa com um ISRS (Escala de Impressões Clínicas Globais de Melhora 1-2 por pelo menos 3 meses) foram selecionados para o experimento. Os pacientes foram testados em duas ocasiões diferentes separadas por uma semana nas quais os pacientes receberam uma mistura contendo grandes aminoácidos neutros ou com (Depleção de Triptofano Falsa [DTf]; dia controle) ou sem triptofano (dia DTa). Auto relatos de ansiedade e humor, bem como medidas cardiovasculares, foram obtidos ao longo dos testes. Cinco horas e meia após a ingestão da mistura os pacientes foram re-expostos aos seus traumas através do procedimento de imaginação guiada de Pitman. RESLTADOS: Esses procedimentos provocaram elevados escores nas medidas avaliadas em ambos os dias, com respostas significativamente mais intensas no dia DTa conforme avaliado pelas Escalas Visuais Analógicas (DTa 47,57 [21,75] -v- DTf 20,71 [18,4]; p=0,001), Escala de Trauma de Davidson (29,4 [12,7] -v- 15,7 [7,79]; p=0,001), Inventário de Ansiedade de Spielberger versão Estado (28,9 [11,03] -v- 18,5 [10,13]; p=0,066, e Perfis de Estados de Humor (p<0,001). CONCLUSÕES: Esses dados são os primeiros a demonstrar que a depleção de 5HT piora as respostas subjetivas a re-experimentação de memórias traumáticas no TEPT e sugere que o aumento na função da 5HT induzida por ISRSs diminui os sintomas de TEPT, especialmente sob provocação, i.e. 5HT ajuda a mediar a resiliência ao estresse. Além de fornecer insights sobre o como os ISRSs funcionam no TEPT, esses dados também oferecem uma abordagem de potenciais novos tratamentos para esse transtorno / INTRODUCTION: Although Selective Serotonin Reuptake Inhibitors (SSRIs) are the first-line Posttraumatic Stress Disorder (PTSD) treatments their mechanism of action is unclear, but possibly improvement of stress resilience is involved. As serotonin (5HT) helps regulate stress responses in other anxiety disorders, the acute tryptophan depletion (aTD) technique was used to lower brain 5HT in SSRSs-remitted PTSD patients. METHODS: Ten patients with PTSD (Mini-International Neuropsychiatric Interview diagnosed) who had made a full recovery on SSRIs (Clinical Global Impressions Improvement Scale 1-2 for at least 3 months) were enrolled in the experiment. Patients were tested on 2 separate occasions a week apart - each session they received a drink containing large neutral amino acids either with (Sham Depletion [SD]; control day) or no tryptophan (aTD day). Self reports of anxiety and mood, as well as cardiovascular measures, were obtained throughout the tests. At 5.5 hours after the drink subjects were reexposed to their trauma using a modification of Pitmans imagery guided method. RESULTS: These procedures provoked elevated ratings on both days, with significantly more marked responses on the aTD day according to Visual Analogue Scales (aTD 47.57 [21.75] -v- SD 20.71 [18.4]; p=0.006), Davidson Trauma Scale (29.4 [12.7] -v- 15.7 [7.79]; p=0.001), Spielberger State Anxiety Inventory (28.9 [11.03] -v- 18.5 [10.13]; p=0.066, and Profile of Mood States (p<0.001). CONCLUSIONS: These data are the first to show that 5HT depletion worsens the subjective responses to reliving traumatic memories in PTSD and suggest that that SSRI-induced increases in 5HT function restrains PTSD symptoms, especially under provocation, i.e. 5HT helps mediate resilience to stress. As well as giving insights into how SSRIs work in PTSD, these data may also offer a translational approach to potential new treatments for this disorder