In der Behandlung neuropathischer und anderer chronischer Schmerzen werden trizyklische Antidepressiva bereits mit Erfolg eingesetzt, die nebenwirkungsärmeren SSRI zeigen jedoch nur einen mäßigen Erfolg. In dieser Studie gingen wir der Frage nach, inwieweit 5-HTT -/- Mäuse, die als Modell einer lebenslangen Behandlung mit SSRI gelten, in einem chronisch entzündlichen Schmerzmodell ein anderes Schmerzverhalten zeigen als Wild-typen und ob sich auf neuronaler Ebene durch das Ausschalten des 5-HT Transporters Ursachen für ein geändertes Schmerzverhalten finden lassen. Von besonderem Interesse war dabei auch, welche Rolle 5-HT in der peripheren Schmerzvermittlung zukommt. Mit standardisierten Testverfahren wurden die 5-HTT -/- Mäuse und Wildtypmäuse nach i.pl. Injektion von CFA auf zwei Schmerzqualitäten hin untersucht. Die Schmerzschwelle für taktile Reize wurde mit von Frey Haaren bestimmt, zur Testung der Hitzehyperalgesie wurde eine Infrarotwärmequelle benutzt. Anschließend wurden an dem Gewebe immunhistochemische Analysen durchgeführt und mittels HPLC der Gehalt an 5-HT in verschiedenen Gewebeproben bestimmt. Es konnte gezeigt werden, dass Mäuse mit dem Genotyp 5-HTT -/- gegenüber dem Wildtyp von einer durch CFA-Injektion induzierten Hitzehyperalgesie weitgehend unbeeinträchtigt bleiben. Gleichzeitig bestand bei den KO-Mäusen im Vergleich zu den Wildtypen eine deutlichere Abnahme der Hautinnervation sowie eine stärker ausgeprägte Verletzung von DRG-Neuronen, entsprechend einer erhöhten neuronalen Vulnerabilität gegenüber CFA. Im Gewebe der KO-Mäuse fand sich durchweg weniger 5-HT als bei Wildtypen, in DRG-Neuronen der KO-Mäuse war weiterhin weniger BDNF detektierbar. Wir postulieren, dass für die reduzierte Hitzehyperalgesie bei den KO-Mäusen unter anderem der geringere Gewebespiegel von 5-HT und damit folglich in einer Art Ursachen-Wirkungskette auch die geringeren Gewebespiegel von BDNF und 5-HIAA mit ihren entsprechenden Auswirkungen verantwortlich sind. 5-HTT -/- Mäuse als Modell für eine lebenslange Behandlung mit SSRI sind also nicht nur wie kürzlich beschrieben im neuropathischen Schmerzmodell, sondern auch in einem chronisch entzündlichen Schmerzmodell weitgehend vor einer Hitzehyperalgesie geschützt. Unter der Berücksichtigung dieser Daten sollte daher der Einsatz von SSRI in der Behandlung chronischer Schmerzen erneut überprüft werden. / Mice lacking the serotonin transporter (5-HTT-/- mice) develop reduced thermal hyperalgesia after nerve injury, concomitant with reduced serotonin (5-HT) levels in nervous tissue. Here we investigated pain behaviour in 5-HTT-/- mice compared to their wild type littermates after hind paw inflammation induced by complete Freund’s adjuvant (CFA). We used standard tests for pain behaviour, high performance liquid chromatography for measurement of 5-HT, and immunohistochemistry of hind paw skin tissue and L5 dorsal root ganglia (DRG) to measure local inflammation and nerve injury. After intraplantar CFA injection, hyperalgesia to heat was attenuated in 5 HTT-/- mice compared to wild type mice. Their 5-HT levels in nervous and adrenal tissue were reduced. An intraplantar injection of 5-HT four days after CFA transiently brought withdrawal latencies of 5-HTT-/- mice down to the level of wild type mice, thus rescuing the phenotype and supporting the role of 5-HT in the development of CFA-induced thermal hyperalgesia. The density of intraepidermal nerve fibres in plantar skin after CFA injection was reduced to a higher degree in 5-HTT-/- mice than in wild type mice, suggesting greater peripheral nerve injury in the knock-out mice during hind paw inflammation. Accordingly, a higher number of injured DRG neurons was identified by activating transcription factor 3 (ATF3) staining in 5 HTT-/- mice after CFA. We conclude that the phenotype of 5 HTT-/- mice leads to reduced inflammatory pain due to reduced tissue 5-HT levels and to greater peripheral nerve injury after inflammation. Human variants of the 5-HTT genotypes might be part of the factors determining the extent of nerve injury and hyperalgesia in inflammation.

Tübingen, Univ., Diss., 2002.

Recent approaches in depression therapeutics include triple reuptake inhibitors, drugs that target three monoamine systems. Using in vivo electrophysiological and microdialysis techniques, the effects of 2- and 14-day treatments of escitalopram, nomifensine and the co-administration of these two drugs (TRI) were examined in male Sprague-Dawley rats. Short- and long-term TRI administration decreased NE firing and had no effect on DA neurons. Normal 5-HT firing rates were maintained after 2-day TRI administration compared to the robust inhibitory action of selective serotonin reuptake inhibitors (SSRIs). Escitalopram treatment enhanced the tonic activation of the 5-HT1A receptors given the increase in firing observed following WAY100635 administration. Nomifensine treatment enhanced tonic activation of the α2–adrenoceptors following idazoxan administration. TRI treatment caused a robust increase in extracellular DA levels that was in part mediated by a serotonergic contribution. Therapeutic effects of the drugs examined in this study may be due to the enhancement of 5-HT, NE and/or DA neurotransmission.

This study compared auditory behavioral and physiologic measures in normal control subjects and subjects prescribed with a selective serotonin reuptake inhibitor (SSRI) who were yet to take the drug and those currently taking an SSRI. Test measures used were pure tone averages (PTA), acoustic reflex thresholds, uncomfortable loudness levels (UCL), otoacoustic emissions, masking level difference, temporal integration, amplitude resolution, and Beck Depression Inventory-II (BDI-II) scores. Results indicated that there was a significant difference in the amplitude resolution of the unmedicated group when compared to the medicated and the control group. There was also a significant positive correlation between dynamic range (difference between UCL and PTA) and amplitude resolution. The BDI-II revealed a significant difference between the scores of the unmedicated and the control group as well as the medicated and the control group. Although other test measures indicated differences between the groups, the differences were not statistically significant.

Recent approaches in depression therapeutics include triple reuptake inhibitors, drugs that target three monoamine systems. Using in vivo electrophysiological and microdialysis techniques, the effects of 2- and 14-day treatments of escitalopram, nomifensine and the co-administration of these two drugs (TRI) were examined in male Sprague-Dawley rats. Short- and long-term TRI administration decreased NE firing and had no effect on DA neurons. Normal 5-HT firing rates were maintained after 2-day TRI administration compared to the robust inhibitory action of selective serotonin reuptake inhibitors (SSRIs). Escitalopram treatment enhanced the tonic activation of the 5-HT1A receptors given the increase in firing observed following WAY100635 administration. Nomifensine treatment enhanced tonic activation of the α2–adrenoceptors following idazoxan administration. TRI treatment caused a robust increase in extracellular DA levels that was in part mediated by a serotonergic contribution. Therapeutic effects of the drugs examined in this study may be due to the enhancement of 5-HT, NE and/or DA neurotransmission.

Recent approaches in depression therapeutics include triple reuptake inhibitors, drugs that target three monoamine systems. Using in vivo electrophysiological and microdialysis techniques, the effects of 2- and 14-day treatments of escitalopram, nomifensine and the co-administration of these two drugs (TRI) were examined in male Sprague-Dawley rats. Short- and long-term TRI administration decreased NE firing and had no effect on DA neurons. Normal 5-HT firing rates were maintained after 2-day TRI administration compared to the robust inhibitory action of selective serotonin reuptake inhibitors (SSRIs). Escitalopram treatment enhanced the tonic activation of the 5-HT1A receptors given the increase in firing observed following WAY100635 administration. Nomifensine treatment enhanced tonic activation of the α2–adrenoceptors following idazoxan administration. TRI treatment caused a robust increase in extracellular DA levels that was in part mediated by a serotonergic contribution. Therapeutic effects of the drugs examined in this study may be due to the enhancement of 5-HT, NE and/or DA neurotransmission.

The discovery of stem and progenitor cells capable of ongoing neurogenesis in the adult mammalian brain has raised hope that we will one day be able to harness their intrinsic regenerative capacity following injury. Development of such therapeutic strategies relies on a comprehensive understanding of the underlying regulation of the neurogenic process. To this end, I show, in this thesis, that cultured post-natal hippocampal neural progenitor cells (NPCs) express a specific repertoire of connexins (Cx), a family of channel forming proteins critical for communication prior to the development of functional chemical synapses. I show that this pattern of Cx expression, specifically Cx43 and Cx45, is modulated by interaction with the extracellular matrix component laminin providing evidence of extracellular matrix-cell interaction in the regulation of intrinsic Cx expression and function in postnatal NPCs. In adult brain, I show, for the first time, that Cx45 localizes to all cell types of the neuronal lineage with the exception of the type 3 doublecortin (DCX)-positive NPCs. Using a loss of function approach, I show that this expression is required for the normal proliferation of type 1 nestin and glial fibrillary acidic protein-positive stem like NPCs but not for the differentiation or survival of their progeny in the adult hippocampus. With respect to exogenous pharmacological cues that influence hippocampal neurogenesis, this thesis also demonstrates that chronic treatment with a sub-set of selective serotonin reuptake inhibitor antidepressants, fluoxetine and escitalopram, increases the proliferation but not the survival of adult NPCs in healthy, non-depressed mice. Further, standard post-operative analgesia with the opiate buprenorphine inhibits the proliferation of DCX-positive adult NPCs and increases the survival of their progeny. Finally, over the course of the research for this thesis, it became clear that exposing research animals to even very subtle environmental changes can influence the basal neurogenic process. Ultimately this work further highlights the exquisite sensitivity of the regulation of what is already recognized to be a highly dynamic process and provides important insight into the neurogenic process that can be used to inform future therapeutic development and application.

Das Verordnungsvolumen von Antidepressiva in Deutschland hat sich in den letzten zehn Jahren etwa verdoppelt. Gleichzeitig liegen zahlreiche Untersuchungen über erhöhte Blutungstendenzen unter der Therapie mit serotonergen Antidepressiva vor. Die aktuelle Studienlage deutet darauf hin, dass es unter anderem über das serotonerge System zu Beeinflussungen der Thrombozyteneigenschaften und in Folge dessen zu Veränderungen der Blutgerinnung kommen könnte. Ziel der vorliegenden Arbeit war es, den Zusammenhang zwischen der Serumkonzentration serotonerger Antidepressiva und der Blutgerinnung zu untersuchen. Im Gegensatz zur Dosis bietet die Serumkonzentration exakte Informationen über die tatsächlich wirkende Antidepressivamenge und berücksichtigt neben der Patientenadhärenz die interindividuelle Variabilität der pharmakokinetischen Eigenschaften. Die Beurteilung der Blutgerinnung erfolgte unter Zuhilfenahme von Gerinnungsparametern (Thrombozytenzahl, mittleres Plättchenvolumen, Quick, INR, partielle Thromboplastinzeit). Es wurde die Hypothese aufgestellt, dass mit steigender Serumkonzentration Veränderungen der Blutgerinnung und in Folge dessen auch der Gerinnungsparameter entstehen können. Darüber hinaus sollte untersucht werden unter welchen Antidepressiva potentielle Veränderungen auftreten. Es wurden Antidepressiva unterschiedlicher Wirkungsgruppen analysiert: Amitriptylin, Doxepin, Es‑Citalopram, Mirtazapin und Venlafaxin. Besonders selektive Serotonin-Wiederaufnahmehemmer standen auf Grund der aktuellen Studienlage im Verdacht Einfluss auf die Gerinnung zu nehmen. Um Antidepressiva spezifische Aussagen treffen zu können, war das Vorliegen einer antidepressiven Monotherapie grundlegendes Selektionskriterium. Alle potenziell gerinnungsbeeinflussenden sowie serotonerg wirkenden Arzneimittel wurden ausgeschlossen. Die Daten wurden retrospektiv erhoben und stammten von stationär therapierten Patienten der Klinik für Psychiatrie, Psychosomatik und Psychotherapie am Universitätsklinikum Würzburg. Die Untersuchungen ergaben für das trizyklische Antidepressivum Amitriptylin signifikante Ergebnisse. Die interindividuelle Analyse zeigte signifikant positive Korrelationen zwischen der partiellen Thromboplastinzeit (PTT) und dem Metabolitenspiegel (Nortriptylin‑Konzentration, rs=0,564; p=0,010, N=20) sowie dem Summenspiegel von Amitriptylin (Amitriptylin- und Nortriptylin‑Konzentration, rs=0,477; p=0,033, N=20). Darüber hinaus stellten sich im Rahmen der intraindividuellen Analyse signifikante Unterschiede zwischen der Thrombozytenzahl unter niedriger und hoher Amitriptylin‑Konzentration dar (Z= ‑2,867; p=0,004, N=45). Ergänzend wurde im Rahmen von explorativen Untersuchungen der Zusammenhang zwischen der verabreichten Dosis und der Serumkonzentration der Antidepressiva analysiert. Die Ergebnisse zeigten Schwankungen um den Faktor 3 bis 11, die im Vergleich zu anderen Studien geringer ausfielen. Der Verdacht, dass besonders selektive Serotonin-Wiederaufnahmehemmer einen erhöhten Einfluss auf die Gerinnungsparameter haben, wurde in der aktuellen Arbeit nicht bestätigt. Ebenso waren unter Doxepin, Mirtazapin und Venlafaxin keine Zusammenhänge zur Serumkonzentration zu beobachten. Die signifikanten Ergebnisse unter Amitriptylin lassen vermuten, dass nicht nur die Inhibition von Serotonintransportern, wie bei selektiven Serotonin-Wiederaufnahmehemmern, sondern zusätzlich auch die Hemmung von Serotoninrezeptoren, wie dem 5‑HT2A‑Rezeptor, eine Rolle im Hinblick auf Veränderungen von Thrombozyteneigenschaften spielen. Dennoch lagen im Rahmen dieser Untersuchung 98% der Gerinnungsparameter aller analysierten Antidepressiva im Normbereich. Die Ergebnisse legen die Vermutung nahe, dass das Risiko immer wieder berichteter Blutungskomplikationen unter der Behandlung mit Antidepressiva trotz zunehmender Verordnungszahlen überschaubar scheint. Entsprechend aktueller Publikationen ist vermutlich erst bei zusätzlicher Einnahme von nichtsteroidalen Antirheumatika sowie antikoagulativen Arzneimitteln von einem erhöhten Blutungsrisiko auszugehen. Besonders gastrointestinale Blutungen spielen bei Kombination dieser Medikamente auf Grund der gesteigerten Magensäuresekretion eine Rolle. Ob die Serumkonzentration der Antidepressiva bei entsprechender Komedikation ebenfalls eine Rolle im Hinblick auf Veränderungen der Gerinnungsparameter spielt, sollte im Rahmen weiterführender Längsschnittstudien genauer untersucht werden. Ergänzend wären Untersuchungen zur Klärung des Kausalzusammenhangs wünschenswert, um das Blutungsrisiko im Zusammenhang mit Antidepressiva in Zukunft weiter minimieren zu können. / Introduction: The prescription of antidepressants has increased worldwide in recent years. Treatment with serotonergic antidepressants has been associated with enhanced risk of bleeding. Correlations to serum concentrations of antidepressants have not been investigated in detail. Methods: Serum concentrations of amitriptyline (AMI), doxepin (DOX), escitalopram (ESC), mirtazapine (MIR) and venlafaxine (VEN) as well as coagulation parameters in 507 patients were retrospectively evaluated in the Department of Psychiatry, Psychosomatics and Psychotherapy at the University Hospital of Würzburg. The coagulation parameters assessed were: platelet count (PLC), mean platelet volume (MPV), prothrombin time (PT), international normalized ratio (INR) and partial thromboplastin time (PTT). The main inclusion criterion was an antidepressant monotherapy. Results: In interindividual analysis significant correlations were observed between PTT and NOR (p=0.010) as well as between PTT and AMI+NOR (p=0.033). Intraindividual analyses showed significant differences of PLC between low and high concentrations of AMI+NOR (p<0.01). For DOX, ESC, MIR and VEN, no statistical significances were found. Discussion: The majority of publications about changes in coagulation during antidepressant drug therapy only considers selective serotonin reuptake inhibitors (SSRI). Nevertheless, as AMI has serotonin transporter and receptor inhibiting properties, significant correlations with PTT and PLC were found. However, since coagulation parameters in all samples were within the normal range, a rather low increase of bleeding risk by antidepressant monotherapy is assumed. The results of our study support the assumption that the documented bleeding events of recent studies are mainly due to the combined use of antidepressants, non-steroidal anti-inflammatory drugs and platelet aggregation inhibitors.

Post-traumatic stress disorder (PTSD) is a psychological disorder that can cause great social/economic hardship. Progress towards treating PTSD has been slow due to a lack of understanding of its pathogenesis. This dissertation aimed to address this issue by investigating the involvement of the astrocytic glutamate reuptake transporter, GLT-1, and regional differences in expression of NMDA receptor subtypes in the development of a rat model of PTSD. We hypothesized that impaired astrocytic glutamate reuptake inhibits long-term memory processes, and that concurrent presence of glucocorticoids (GCs) during situational trauma selectively inhibits fear extinction memory processes in the prefrontal cortex, but not of conditioned fear memory processes in the amygdala, due to differences between these brain regions in expression of NMDA receptor subtypes. The effect of GLT-1 manipulation was studied in vivo. Utilizing the Single Prolonged Stress (SPS) model of PTSD, rats were either exposed to SPS or not. Within these groups, rats were administered a saline sham, a GLT-1 facilitator (ceftriaxone (CEF)), or a GLT-1 inhibitor (dihydrokainic acid (DHK)). Using Classical Fear Conditioning (CFC) and Fear Extinction (EXT) paradigms, retention of fear extinction memories was measured to determine the effect of GLT-1 manipulation on SPS-induced behavior (i.e., impaired fear extinction retention). From the brain of each rat, the amygdala, hippocampus, and prefrontal cortex (PFC) were collected and expression of GLT-1, p-CREB (a molecular indicator of long-term memory), and glucocorticoid receptor (GR, a molecular indicator of a PTSD-like state) were quantified. Analysis of the behavioral data showed that SPS exposure alone reduced the retention of extinction memories, but CEF and DHK both eliminated this effect. Analysis of the brain tissues revealed that SPS induced an increase in GR expression in the hippocampus. SPS also increased GLT-1 expression, but not p-CREB, in the PFC and amygdala. To evaluate the involvement of regional differences in NMDA receptor subtype expression ex vivo, tissue sections of amygdala, hippocampus, and PFC were taken from SPS and non-SPS exposed rats. Synaptic transmission was stimulated in these tissues using bicuculline in the presence of glucocorticoids, NVP-AA077 (a NR2A NMDA receptor subtype inhibitor), or Ro-25 (a NR2B NMDA receptor subtype inhibitor). P-CREB was measured in the tissues treated with GCs to determine if GCs exert greater inhibition of long-term memory in the PFC (a region reported to express high NR2A) than in the amygdala (a region reported to express high NR2B). P-CREB was also measured in the tissues treated with NVP or Ro-25 to determine if these reported receptor profile differences could be demonstrated, and if they changed following SPS exposure. Contrary to the stated hypothesis, analysis of non-SPS exposed rats revealed that GCs, NVP, and Ro-25 decreased p-CREB in all three regions with no differences between regions. However, in the SPS exposed group, p-CREB was not decreased in PFC and hippocampal tissues treated with GCs, amygdalar and PFC tissues treated with NVP, and PFC tissue treated with Ro-25. Overall, the results of the in vivo experiment did not convincingly demonstrate a role of glutamate spill-over in the pathogenesis of PTSD, but did show that modulation of glutamate reuptake can mitigate some of the behavioral consequences of exposure to situational trauma. The results of the ex vivo experiment did not reveal evidence that regional differences in NMDA receptor profiles exist across the three regions analyzed, nor did they show that GCs exert a region specific inhibition of long-term memory formation. However, it was demonstrated that SPS may affect long-term memory by altering expression of synaptic NMDA receptors. This study provides evidence that glial cells may play a role in the pathogenesis of PTSD, and thus may serve as targets for future therapy. / Ph. D.

This thesis aims to review if there is an association between antidepressants and caries in children and adolescents. Previous established evidence exhibits that adults prescribed tricyclic antidepressants have an increased risk of caries. Simultaneously, a global trend of increased prescriptions of antidepressant medications is seen. In Sweden during 2018, 0–17-year old’s on antidepressant medication represented 1,6% percent of the total population. It is of utmost relevance to investigate the association between antidepressants and caries as the increasing population of medicating children may lead to an increased caries prevalence. A systematic literature review was performed in accordance with PRISMAs guidelines. The title-abstract and keywords searches were conducted in the following seven bibliographic databases: PubMed, EMBASE, CINAHL, Scopus, Web of Science, PsycINFO and MedLine. The search consisted of blocks based on “caries”, “children” and “antidepressants”. Unique articles were reviewed from title and abstract. Articles that met the criteria were reviewed in full text. The search generated 1829 unique articles, 1891 were excluded from the predefined criteria. 10 articles were reviewed in full text. None of the articles were eligible within the criteria of inclusion. The conclusion is that further research is needed in this area to assess the possible association between antidepressants and caries in children and adolescents. / Uppsatsen syftar till att sammanställa forskningsläget för sambandet mellan antidepressiv medicinering och karies hos barn och ungdomar. Tidigare evidens visar att vuxna som medicinerar med tricykliska antidepressiva har ökad kariesrisk. Samtidigt kan man globalt se en generell förskrivningsökning av antidepressiva. I Sverige under 2018, utgjorde användarna av antidepressiva i åldersgruppen 0–17 år 1,6% av totalpopulationen. Det är av högsta relevans att undersöka om det finns en potentiell association mellan antidepressiva och karies finns då den ökande populationen av medicinerande barn kan medföra ökad kariesprevalens. En systematisk litteraturöversikt genomfördes enligt PRISMAs riktlinjer. Titel- sammanfattnings och nyckelordssökningen utnyttjade följande sju elektroniska databaser: PubMed, EMBASE, CINAHL, Scopus, Web of Science, PsycINFO och MedLine. Sökningen utfördes i block utifrån “karies”, “barn” och “antidepressiva”. Unika artiklar granskades utifrån titel och abstrakt. Artiklar som uppfyllde förutbestämda kriterier för inklusion granskades i fulltext. Utifrån sökningen påträffades 1829 unika artiklar, varav 1819 exkluderades utifrån från titel och abstrakt. 10 artiklar granskades i fulltext och vi konstaterade att ingen artikel uppfyllde kriterierierna. Slutsatsen för studien är att fler studier och mer forskning behövs inom området. Detta för att kunna svara på om det finns ett samband mellan antidepressiva och karies hos barn.