Irritable bowel syndrome (IBS) är en av de vanligaste diagnostiserade GI-tillstånden idag och är en störning av gastrointestinalkanalen (GI-kanalen). Det finns inget botemedel mot IBS på grund av att patogenesen är oklar och därför är fokusen symtomlindring vid behandling.  De vanligaste symtom som förekommer är buksmärta, obehag i buk, uppblåsthet, utspänd buk och förändring av avföringens konsistens och frekvens. Patofysiologin är inte fullt klarlagd men en rubbning i tarm-hjärn-axeln kan leda till förändring i GI-rörelser. Neurotransmittorerna noradrenalin och serotonin (5-HT) är troligen viktiga faktorer för patofysiologin kopplad till tarm-hjärn-axeln. Syftet var att undersöka effektiviteten och säkerheten för de antidepressiva läkemedlen vid behandling av IBS. De antidepressiva som undersöktes i arbetet var tianeptin, amitriptylin, escitalopram, venlafaxin, vortioxetin och mirtazapin. De fem artiklarna som användes i detta arbete upptäcktes med hjälp av databaserna Pubmed och Onesearch. Sökord som användes var ”IBS” AND ”antidepressants” och ”IBS” AND ”SSRI”.  Alla antidepressiva visade en signifikant förbättring för livskvalitén hos deltagarna i studierna. Tianeptin, amitriptylin, escitalopram, venlafaxin och mirtazapin undersökte förändring av buksmärta och alla hade en signifikant förbättring förutom escitalopram. Escitalopram jämfördes mot rektal ballongutvidgning vid behandling hos IBS med förstoppning (IBS-C). Ballongutvidgningen visade bättre resultat än escitalopram och denna jämförelse gör det svårt att dra någon slutsats om escitalopram i arbetet. Amitriptylin, tianeptin och mirtazapin undersökte förändring av avföringskonsistensesn och frekvensen och visade en signifikant förbättring hos IBS med diarré (IBS-D). Venlafaxin visade signifikant förbättring för både lös och hård avföringsfrekvens och studerade ingen specifik IBS-grupp. Vortioxetin undersökte alla IBS-grupper och endast förändring av livskvalitén, depression och ångest vilket också gör det svårt att dra slutsats om effekt hos IBS. Det var inga av de depressiva medlen som gav allvarliga biverkningar, dock kan vissa biverkningar tolkas som mer obehagliga än andra. För vissa antidepressiva var det deltagare som avslutade studien på grund av biverkningar. Amitriptylin, tianeptin, venlafaxin vortioxetin och mirtazapin visade alla god effekt och säkerhet. Om effektiviteten ock säkerheten jämförs bland dessa har tianeptin det bästa resultatet. / Irritable bowel syndrome (IBS) is one of the most diagnosed conditions in the gastrointestinal (GI) tract today and is a disorder of the GI tract. There is no cure for IBS, which is probably due to the fact that the pathogenesis is unclear, and therefore the focus has been a symptom-relieving treatment. The most common symptoms that occur are abdominal pain, abdominal discomfort, bloating, distension of the abdomen, and change in the consistency and frequency of the stool. The pathophysiology is not fully understood, but a disorder of the gut-brain axis can lead to a change in GI movements. The neurotransmitters norepinephrine and serotonin (5-HT) are probably important factors for pathophysiology and linked to the gut-brain axis.  The aim was to investigate the effectiveness and safety of antidepressants used in IBS treatment. The antidepressants examined in this literature were tianeptine, amitriptyline, escitalopram, venlafaxine, vortioxetine, and mirtazapine. The five articles on which current litter tour work is based were obtained using the PubMed and OneSearch databases. Keywords used were "IBS" AND "antidepressants" and "IBS" AND "SSRI."  All the antidepressants examined showed a significant improvement in the participants' quality of life in the studies. The studies also examined changes in abdominal pain using tianeptine, amitriptyline, escitalopram, venlafaxine, and mirtazapine. All participants showed a significant improvement and reduced abdominal pain except when ingesting escitalopram. Intake of escitalopram was compared against rectal balloon enlargement as a treatment for IBS with constipation (IBS-C). The balloon expansion showed better results than escitalopram, and this comparison makes it difficult to draw any conclusion about escitalopram and its actual effect in different types of IBS. Amitriptyline, tianeptine, and mirtazapine investigated stool consistency and stool frequency changes and showed a significant improvement in these symptoms in IBS with diarrhea (IBS-D). Venlafaxine showed significant improvement for both loose and hard stool frequency; however, no specific IBS group was studied in this study. When ingesting vortioxetine, all different IBS groups and changes in quality of life, depression, and anxiety were examined, making it difficult to conclude about the effect of the drug in IBS. None of the antidepressant medicines produced severe side effects. However, some side effects can be interpreted as more unpleasant than others, and hence there was some loss during some studies.  Amitriptyline, tianeptine, venlafaxine vortioxetine, and mirtazapine showed good efficacy and safety. If the effectiveness and safety were to be compared between these drugs, tianeptine would be the first choice in treating IBS.

Serotonin gilt als Hauptangriffsstelle gängiger Antidepressiva bei schweren Depressionen, wie bspw. selektive Serotonin-Wiederaufnahmehemmer (SSRI), und -Enhancer (SSRE). Es bleibt offen, ob SSRI / E ausschließlich über die Manipulation des Serotoninspiegels wirken, oder ob alternative Signalwege daran beteiligt sind. Ansatzpunkte hierfür sind beispielsweise die neurotrophen Signalwege (spez. Brain derived neurotophic factor, BDNF) oder die Hypothalamus-Hypophysen-Nebennieren- (HPA) – Signalwege des Stressachsensystems. Ebenfalls wurde in Nagetiermodellen beobachtet, dass mit der Dysregulation des zentralen Serotoninsystems bei schweren Depressionen, ein Rückgang der Neurogenese im Gyrus dentatus des Hippocampus einhergeht. Ziel dieser Arbeit war, das Zusammenspiel von Serotonin, BDNF, adulter Neurogenese und der Stressachse zu untersuchen. Zentrum der Studien ist ein Mausmodell, mit einer genetischen Depletion des zentralen Serotonin-synthetisierenden Enzyms Tryptophanhydroxylase 2 (sog. Tph2-/- Mäuse). Es wurden die physiologische Reaktionen auf die Behandlung mit gängigen Antidepressiva abhängig von der Abwesenheit von Serotonin untersucht, um mögliche alternative Signalwege aufzeigen zu können. Die bekannte Zunahme der Neurogenese nach SSRI/SSRE-Behandlung wurde in Wildtyptieren beobachtet, während die Therapie in Tph2-/- Mäusen keine direkte kausale Wirkung zeigte. Im Gegensatz dazu waren die BDNF-Spiegel in depressionsrelevanten Hirnregionen in Tph2-/- Mäusen nach SSRI, signifikant verringert. Auch zeigen die Studien eine neurobiologische Relevanz von Serotonin im ZNS, bei den antidepressiven Mechanismen einer Elektrokonvulsiven Krampftherapie. Ebenfalls deuten erhöhte Neurogeneseraten bei lebenslanger Abwesenheit von Serotonin im ZNS, Therapiemethoden-unabhängig, möglicherweise auf eine modulierte Stressreaktion hin. Untersuchungen der Parameter des HPA-Stressachsensystems, wiesen auf einen grundlegend veränderten Stresshormonspiegel in Tph2-/- Mäusen hin. / Serotonin, the "molecule of happiness" is an important target for antidepressants. The mainly prescribed drugs in major depression are selective serotonin re-uptake inhibitors (SSRI); but recently, SSR-enhancer (SSRE) have also attracted clinical attention. However, only a quarter of patients responds to treatment. It needs to be determined, whether SSRI/E act solely via manipulating serotonin levels or whether other pathways are involved, e.g. neurotrophic signaling (brain-derived neurotrophic factor, BDNF) or the hypothalamus-pituitary-adrenal (HPA)-axis. Furthermore, in major depression, dysregulation of central serotonin signaling is accompanied with a decline in hippocampal neurogenesis, as has been observed in rodent models. At the center of this thesis is a mouse model deficient in the central serotonin-synthesizing enzyme, tryptophan hydroxylase 2 (Tph2-/- mice). I have investigated physiological responses to antidepressant treatment in the absence of brain serotonin, and the possible role of alternative pathways. I observed the typical increase in neurogenesis upon SSRI treatment in WT mice, while it had no effect in Tph2-/- mice. In contrast, BDNF levels were significantly decreased in Tph2-/- mice after treatment with no effect in WT control mice. Furthermore, my results show a critical role of brain serotonin in the neurobiological effects of electroconvulsive seizure. Surprisingly, in animals lacking central serotonin, increased neurogenesis was observed independently of the treatment. The gathered data indicated an altered stress response; therefore, parameters of the HPA-axis have been studied, indicating a downregulated HPA system in Tph2-/-animals in baseline state, but showed no difference in treatment or feedback control. This thesis gives insight into the mechanisms of antidepressant action and reveals ideas for novel pathways involved in the process that could be used as targets in therapeutic approaches and further research in major depression.