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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Neuroendocrine control of maternal behaviour

Caughey, Sarah Dawn January 2011 (has links)
Maternal behaviour during the peri-partum period, albeit in differing forms, can be observed in all mammals, thus it must serve an important evolutionary purpose in enabling the successful raising of offspring. Maternal behaviour is comprised of a large suite of behaviours; in rodents these are generally defined as lactation, pup retrieval, maternal aggression and pup grooming. The maternal behaviour circuitry involves many brain regions including the hypothalamus and the limbic system which work together to regulate the motor, motivational and emotional demands of the lactation period. The main aim of this thesis is to understand how different neuromodulators, specifically oxytocin (OXT), vasopressin (AVP), allopregnanolone (AP) and GABA, influence the expression of maternal behaviour, especially maternal aggression, and where in the brain they act to control this. Maternal aggression in rats changes dramatically throughout pregnancy, parturition and lactation. This expression is highly influenced by pups and during early lactation, pup cues are essential in maintaining it. Towards the end of lactation pup cues appear to result in the down regulation of maternal aggression. The maternal aggression circuitry is highly complex and involves many of the brain regions highlighted to be involved in maternal behaviour. The neuropeptides, OXT and AVP, are observed to have significant changes in their systems that correlate with maternal aggression, specifically within the BnST and PVN. This leads to the proposal they work oppositely to control maternal aggression by regulating fear and anxiety in the lactating rat. There is also evidence the OXT system mediates the motor output of maternal aggression. AP and GABA are also important in maternal behaviour, especially in relation to fear; whether this in context with OXT to enable maternal aggression or if they are a back up mechanism for OXT secretion malfunctioning remains to be determined. By understanding the complex maternal behaviour neural circuitry and how neuromodulators work to control it, enables the development of potential therapies for disorders a woman may experience during the peri-partum period. Prevention of these disorders is not only beneficial to the mother and her immediate family but is also crucial for her offspring’s development in prevention of adulthood disorders stemming from their childhood experience which can impact their own paternal or maternal care ability.
2

The effects of neurosteroids and neuropeptides on anxiety-related behavior

Engin, Elif 11 1900 (has links)
Anxiety disorders are the most prevalent of all psychiatric conditions. However, current pharmacological treatments for anxiety disorders are characterized by one or more of the following deficiencies: 1) unwanted side effects, 2) partial efficacy, 3) addictive potential, and 4) delayed onset of therapeutic effects. These therapeutic liabilities motivate the search for better pharmacological treatments. This research effort has been concentrated in three broad, neuropharmacological domains: 1) Sub-unit specific GABAA receptor agonists, 2) Neurosteroids, and 3) Neuropeptides. The general purpose of this thesis was to advance our understanding of the putative anxiolytic potential of neurosteroids and neuropeptides, and their neural mechanisms of action, as revealed by intracerebral infusion studies in animal models of anxiety. Chapter 1 of this thesis will provide a systematic review of what is now known about the behavioral effects of intra-cerebrally infused agonists and antagonists of anxiolytic compounds in animal models of anxiety. A theoretical context in which to view the empirical work is also outlined. Chapter 2 will provide a brief introduction to neurosteroids and neuropeptides, and their potential as anxiolytic drugs as suggested by the current literature. In Chapter 3, the anxiolytic-like effects of the neurosteroid allopregnanolone were examined in the amygdala, the hippocampus or the medial prefrontal cortex. Allopregnanolone had site- and test-specific anxiolytic effects, causing anxiolysis following infusion into the amygdala and the medial prefrontal cortex. In Chapter 4, the anxiety-related effects of two receptor antagonists of the neuropeptide arginine vasopressin were investigated in the hippocampus. Anxiolytic effects were specific to both receptor sub-type and by infusion site. In chapter 5, the putative anxiolytic and antidepressant effects of the neuropeptide somatostatin were investigated. Intracerebroventricular microinfusion of somatostatin produced anxiolytic-like and antidepressant-like signatures in distinct domains. In chapter 6, selective agonists for each of the 5 G-protein coupled somatostatin receptors were administered to rats. Intracerebroventricular administration of an sst2 agonist produced anxiolytic-like effects, whereas an antidepressant-like effect was observed following the administration of both sst2 and sst3 agonists. In summary, the present thesis provides important clues to the neurochemical correlates of anxiety, and its potential treatment with alternative compounds such as neuropeptides.
3

The effects of neurosteroids and neuropeptides on anxiety-related behavior

Engin, Elif Unknown Date
No description available.
4

Allopregnanolone and mood : studies of postmenopausal women during treatment with progesterone

Andréen, Lotta January 2006 (has links)
Introduction. Allopregnanolone and pregnanolone (neuroactive metabolites of progesterone) act as positive modulators of the GABAA receptor system which is the major inhibitory system in CNS. Contradictory results on the effect of GABAA receptor modulators are reported. Beneficial properties such as anaesthesia, sedation, and anxiolysis are reported as well as adverse, anxiogenic and aggressive effects. It has been suggested that GABAA receptor agonists have bimodal effects. Low concentrations increase an adverse, anxiogenic effect, whereas higher concentrations show beneficial, calming properties. Aims. To investigate if progesterone treatment induces adverse mood in postmenopausal women and if the severity in mood symptoms is related to progesterone, allopregnanolone or pregnanolone serum concentrations. To evaluate differences in steroid concentrations induced by different doses and routes of administration of progesterone. Methods. Two randomised, placebo-controlled, double-blind crossover studies of postmenopausal women were performed. Subjects were treated with estradiol continuously. Different doses of progesterone, given vaginally or orally, were added sequentially during the last 14 days of each treatment cycle. Daily symptom ratings were kept using a validated rating scale. Blood samples for progesterone, allopregnanolone and pregnanolone analyses were collected during each treatment cycle. A study regarding the pharmacokinetics after ingestion of low-dose oral progesterone was conducted with postmenopausal women. Blood samples for the analyses of progesterone, allopregnanolone and pregnanolone were collected and pharmacokinetic parameters were calculated. Results. Certain postmenopausal women on sequential HT with vaginal and oral progesterone experience mood deterioration during the progesterone phase while on a low dose of progesterone but not on higher doses or the placebo. Negative mood symptoms occurred when the serum concentration of allopregnanolone was similar to endogenous luteal phase levels, whereas lower and higher concentrations had no effect on mood. Pharmacokinetic analyses show that low-dose oral progesterone can be used as a prodrug to allopregnanolone when the aim is to achieve physiological concentrations of allopregnanolone. Conclusions. A bimodal association between allopregnanolone concentration and adverse mood is observed in postmenopausal women treated with progesterone. The addition of low-dose progesterone to estradiol induces adverse mood in postmenopausal women, whereas higher doses and placebo have no mood-deteriorating effect.
5

GABA-steroid effects in healthy subjects and women with polycystic ovary syndrome / GABA-steroid effects : in healthy subjects and women with polycystic ovary syndrome

Hedström, Helena January 2011 (has links)
Background: The progesterone metabolite allopregnanolone is involved in several clinical conditions in women, e.g. premenstrual dysphoric disorder. It is a very potent GABA-steroid with GABA-A receptor effects similar to other GABA-agonists, e.g. benzodiazepines, and it causes sedation. An objective way to examine effects on the GABA-A receptor in humans is to measure saccadic eye velocity (SEV), which is reduced by GABA-agonists, e.g. allopregnanolone. Animal studies suggest that allopregnanolone is involved in the regulation of gonadotropin secretion via the GABA-A receptor, but this has not been studied in humans. Polycystic ovary syndrome (PCOS) is the most common endocrine disturbance among women of fertile age (5–10%), characterized by polycystic ovaries, menstrual dysfunction, hyperandrogenity, and 50% have obesity. Studies have shown higher allopregnanolone levels in overweight people. PCOS women have increased levels of androstanediol, an androgen metabolite which is an GABA-A receptor agonist. Tolerance often occurs when persons are exposed to high levels of GABAergic modulators. It has not been studied whether GABA-A receptor sensitivity in PCOS women is changed. Another progesterone metabolite, isoallopregnanolone, is the stereoisomere of allopregnanolone but has not been shown to have any GABA-A receptor effect of its own. Instead it has often been used to control steroid specificity to allopregnanolone. Aims: To compare the effects of allopregnanolone and isoallopregnanolone on gonadotropin secretion. To compare allopregnanolone levels, GABA-A receptor sensitivity to allopregnanolone and effects on gonadotropin secretion in both cycle phases and PCOS conditions. To examine pharmacokinetics and pharmacodynamic properties for isoallopregnanolone. Method: In the follicular phase healthy women were examined for the effect of allopregnanolone or isoallopregnanolone on gonadotropin secretion. PCOS women and healthy women in both cycle phases were given allopregnanolone and the differences in effects on SEV were examined, as well as changes in serum levels of gonadotropins and allopregnanolone at baseline and during the test day. Pharmacokinetics and GABA-A receptor sensitivity using SEV were explored for isoallopregnanolone in healthy women. Results: Allopregnanolone decreases gonadotropin serum levels in healthy controls in both cycle phases, but has no effect on gonadotropin secretion in women with PCOS. PCOS women have higher baseline serum levels of allopregnanolone than follicular phase controls, but lower levels than luteal phase controls. PCOS women show greater reduction in SEV to allopregnanolone than controls. Isoallopregnanolone has no effect on gonadotropin secretion. There is an effect of isoallopregnanolone on SEV, explained by a metabolism of isoallopregnanolone into allopregnanolone. Conclusion: There are significant differences in the GABA-A receptor response to a GABA-steroid in different endocrine conditions in women of fertile age examined with saccadic eye velocity. The GABA-steroid allopregnanolone decreases gonadotropin serum levels in healthy women but not in PCOS women. The lack of effect on gonadotropins by isoallopregnanolone suggests an involvement of the GABA-A receptor.
6

Characterization of novel mitochondrial modulators for the development of neuroprotective strategies / Caractérisation de nouveaux modulateurs mitochondriaux pour le développement de stratégies neuroprotectrices

Lejri, Imane 27 September 2016 (has links)
Ce travail de thèse a permis la caractérisation de deux familles de modulateurs mitochondriaux: les analogues de l’alloprégnanolone et les nouveaux ligands synthétiques de la protéine de translocation mitochondriale ou translocator protein (TSPO) impliquée dans la neurostéroidogenèse. Nos résultats clés ont montré que: i) in vitro, BR297, un analogue de l'alloprégnanolone atténue les déficits bioénergétiques liés à la maladie d'Alzheimer et présente un effet protecteur contre le stress oxydatif, en réduisant les espèces réactives de l'oxygène et la mort dans un modèle cellulaire de la maladie d'Alzheimer, avec une plus grande efficacité comparé à l’allopregnanolone; ii) in vivo, premièrement l’effet protecteur de BR297 a été confirmé dans un modèle de souris transgénique de la maladie d’Alzheimer en atténuant les déficits mitochondriaux,puis deuxièmement, BR297 et BR351 ont démontré des effets neuroprotecteurs sur les dysfonctionnements mitochondriaux liés à l'âge par l'amélioration de bioénergétique cellulaire et des activités des complexes mitochondriaux; et iii) in vitro, les ligands TSPO représentent des molécules prometteuses qui sont capables d'augmenter bioénergétique cellulaire avec des effets comparable ou plus important que des molécules de référence dans un modèle cellulaire de la maladie d'Alzheimer. / This PhD work allowed the characterization of two families of mitochondrial modulators: novel analogues of allopregnanolone, and novel synthetic ligands of translocator protein (TSPO) implicated in the neurosteroidogenesis. Our key findings showed that: i) in vitro, BR297, an analog of allopregnanolone alleviated Alzheimer’s disease-related bioenergetics deficits and exhibited protective effects against oxidative stress by reducing reactive oxygen species and decreasing death in a cellular model of Alzheimer’s disease,with a higher effectiveness compared to allopregnanolone; ii) in vivo, firstly the protective effect of BR297 was confirmed in the transgenic Tg2576 mouse model by alleviating the mitochondrial deficits, secondly BR297and another analog BR351 demonstrated neuroprotective effects on age-related mitochondrial dysfunctions via enhancement of cellular bioenergetics and complex activities; and iii) in vitro, TSPO ligands represent promising molecules which are able to increase cellular bioenergetics with similar/ or higher effects compared to different reference molecules in a cellular model of Alzheimer’s disease.
7

Multidisciplinary analysis of biological effects of novel analogs of the neurosteroid allopregnanolone : evidence for a proliferative, neurogenic and neuroprotective action / Analyse multidisciplinaire des effets biologiques de nouveaux analogues du neurostéroïde alloprégnanolone : mise en évidence d'une action prolifératrice, neurogénique et neuroprotectrice

Karout, Mona 30 September 2015 (has links)
Ce travail de thèse a permis de caractériser avec succès des analogues structuraux de l´allopregnanolone présentant pour certains d'entre eux des effets bénéfiques et des avantages par rapport à la molécule de référence. En particulier, l'analogue O-allyl-AP, qui stimule in vitro la prolifération des cellules progénitrices, la différenciation neuronale et protège les cellules souches neurales adultes contre l'apoptose induite par le peptide Aβ42, est aussi efficace in vivo pour contrecarrer le déclin de la neurogenèse lié à l'âge et améliorer les performances cognitives au cours du vieillissement. De façon intéressante, les effets proliférateur et neuroprotecteur de l´O-allyl-AP semblent impliquer différents mécanismes d'action. Des expériences supplémentaires sont nécessaires pour conclure sur la capacité de l´O-allyl-AP à stabiliser le déclin de l'activité neurologique et à réduire les caractéristiques physiopathologiques de la Maladie d'Alzheimer (MA) chez les souris Tg2576. Nos résultats ouvrent des perspectives intéressantes pour l'application de l´O-allyl-AP dans le développement de stratégies thérapeutiques contre la MA et les maladies neurodégénératives. / This PhD work allowed us to successfully characterize structural analogs of allopregnanolone. Some of these analogs showed beneficial effects and advantages with respect to the molecule of reference. In particular, the analog O-allyl-AP stimulates proliferation of progenitor cells in different neural in vitro models, neuronal differentiation and protects adult neural stem cells against Aβ-induced apoptosis. In addition, O-allyl-AP is effective in counteracting the decline in neurogenesis related to age and in improving cognitive performance during aging. Interestingly, proliferative and neuroprotective effects seem to involve different mechanisms of action. Additional experiments are needed to confirm our preliminary data about the ability of O-allyl-AP to attenuate the decrease of neurogenic activity and to reduce pathophysiological hallmarks of Alzheimer disease (AD) in Tg2576 mice. Our findings provide interesting perspectives for using O-allyl-AP in the development of therapeutic strategies against AD and other neurodegenerative diseases.
8

Avaliação da Tolerabilidade, do Perfil Hormonal e dos Efeitos Endometrais Secundário à Administração Vaginal do Gel e de Allopregnanolona à Mulheres na Pós-Menopausa, em Uso de Estrogenioterapia: Estudo Fase 2. / Evaluation of the tolerability, hormonal profile and endometrial effects of allopregnanolone, administered in the form of a gel by the vaginal route to postmenopausal women on oral estrogen therapy: phase II study.

Navarro, Paula Andrea de Albuquerque Salles 31 July 2000 (has links)
Objetivos: Avaliar a tolerabilidade e obter dados preliminares referentes aos efeitos endometriais da allopregnanolona, administrada sob a forma de gel, por via vaginal, a pacientes na pós-menopausa em uso de estrogenioterapia oral, ao longo de 2 ciclos de tratamento, assim como obter dados preliminares do efeito da droga de estudo, nos níveis séricos de gonadotrofinas, estradiol e progesterona. Pacientes e métodos: Foram incluídas no presente estudo 13 pacientes na pós-menopausa, divididas em 2 grupos: grupo 1: primeiras 7 pacientes incluídas no estudo (mediana de idade = 52 anos; mediana de tempo de amenorréia = 2 anos ) e grupo 2: 6 últimas pacientes (mediana de idade = 55,5 anos; mediana de tempo de amenorréia = 4,3 anos ). Todas as pacientes foram submetidas a 2 ciclos consecutivos de tratamento, cada qual com 28 dias de duração, utilizando 2 mg ao dia de valerato de estradiol, por via oral, continuamente, associado ao gel de allopregnanolona a 8%, por via vaginal, nos 10 últimos dias de um único ciclo (grupo 1) ou dos 2 ciclos (grupo 2). Todas as pacientes foram avaliadas quanto à caracterização dos efeitos adversos e sangramento genital. Coleta de sangue para dosagens hormonais e biópsias de endométrio foram realizadas no 28o e no 56o dia de tratamento, nas pacientes do grupo 1 e, apenas, no 56o, nas do grupo 2. Resultados: A taxa de aderência ao tratamento foi de 100% nas pacientes de ambos os grupos. A mastalgia foi o efeito adverso mais freqüente (4 casos), seguido pela cefaléia e pela dor abdominal (2 casos cada), todos estes relacionados ao uso do valerato de estradiol. Uma paciente referiu prurido vulvar durante o uso do gel de allopregnanolona. Todos os efeitos adversos foram leves e não interferiram na utilização das medicações prescritas. Não houve diferença significativa (P =1,0) entre as proporções de sangramento genital por deprivação hormonal após um (23,1%) ou dois ciclos de utilização da allopregnanolona (33,3%). Não encontramos diferença significativa (P = 0,27) entre as proporções de endométrio secretor e proliferativo após um (57,1% e 42,9%, respectivamente) ou dois ciclos (16,7% e 66,6%) de uso da allopregnanolona. Contudo há uma aparente redução da percentagem de endométrio secretor após 2 meses de utilização da allopregnanolona, quando comparada a um único ciclo de uso desta droga. Não houve diferença estatisticamente significante entre os níveis séricos de FSH, LH, estradiol ou progesterona após um ciclo com valerato de estradiol exclusivamente, quando comparados a um ou dois ciclos de uso da allopregnanolona. Conclusões: Observamos boa tolerabilidade à administração vaginal do gel de allopregnanolona a mulheres na pós-menopausa, em uso de estrogenioterapia oral com valerato de estradiol, refletida pela baixa incidência de efeitos adversos e pela boa aceitabilidade à terapêutica. Aparentemente, a allopregnanolona não interfere nos níveis séricos de gonadotrofinas, estradiol e progesterona. Estudos com maiores casuística e tempo de seguimento são necessários para se determinar os efeitos endometriais desta nova droga, e, conseqüentemente, da sua possível utilização futura, nos diversos esquemas de terapia de reposição hormonal vigentes. / Objectives: To evaluate the tolerability and to obtain preliminary data regarding the endometrial effects of allopregnanolone, administered in the form of a gel by the vaginal route to postmenopausal women on oral estrogen therapy, along two cycles of treatment, and to obtain preliminary data about the effect of the drug under study on serum gonadotropin, estradiol and progesterone levels. Patients and methods: Thirteen postmenopausal women were divided into 2 groups: group 1: the first 7 patients admitted to the study (median age = 52 years; median time of amenorrhea = 2 years), and group 2: last 6 patients (median age = 55.5 years; median time of amenorrhea = 4.3 years). All patients were submitted to 2 consecutive treatment cycles of 28 days each continuously taking 2 mg estradial valerate a day by the oral route in combination with 8% allopregnanolone gel by the vaginal route during the last 10 days of a single cycle (group 1) or of 2 cycles (group 2). All patients were evaluated in terms of adverse effects and genital bleeding. Blood samples were collected for hormonal measurements and endometrial biopsies were taken on the 28th and 56th days of treatment in group 1 patients and only on the 56th day in group 2 patients. Results: The rate of compliance with treatment was 100% for the patients of both groups. Mastalgia was the most frequent adverse effect (4 cases), followed by headache and by abdominal pain (2 cases each), all of them related to the use of estradiol valerate. One patient reported vaginal pruritus during the use of the allopregnanolone gel by the vaginal route. All adverse effects were mild and none of them interfered with the use of the prescribed medications. There was no significant difference (P = 1.0) between the proportions of genital bleeding due to hormonal deprivation after one (23.1%) or two cycles of allopregnanolone (33.3%). Also, no significant difference (P = 0.27) was found between the proportions of secretory and proliferative endometrium after one (57.1% and 42.9%, respectively) or two cycles (16.7% and 66.6%) of allopregnanolone. However, there was an apparent reduction in the percentage of secretory endometrium after 2 months of allopregnanolone compared to a single cycle of this drug. There was no significant difference between serum FSH, LH, estradiol or progesterone levels after one cycle with estradiol valerate exclusively, compared to one or two cycles of allopregnanolone. Conclusions: We observed good tolerability of vaginal administration of allopregnanolone gel to menopausal women on oral estrogen treatment with estradiol valerate, as shown by the low incidence of adverse effects and by the good acceptability of treatment. Apparently allopregnanolone does not interfere with serum gonadotrophin, estradiol or progesterone levels. Studies on a larger series and with a longer follow-up time are needed to determine the endometrial effects of this new drug and consequently the possibility of its future use in the different schemes of hormonal replacement therapy currently available.
9

Neuroactive steroids and rat CNS

Birzniece, Vita January 2004 (has links)
Several studies suggest profound effects on mood and cognition by neuroactive steroids. Estrogen alone or in combination with antidepressant drugs affecting the serotonin system has been used to treat mood disorders. On the other hand, progesterone is related to negative effects on mood and memory. A major part of the progesterone effects on the brain can be mediated by its metabolite allopregnanolone, which is also de novo synthesized in the brain, and affects the GABAA receptors. It would be of great importance to find a substance that antagonize allopregnanolone adverse effects. To investigate how long term supplementation of estradiol and progesterone, resembling postmenopausal hormone replacement therapy, affects serotonin receptors in different brain areas important for mood and memory functions, we used ovariectomized female rats. After 2 weeks of supplementation with 17β-estradiol alone or in combination with progesterone, or placebo pellets, estradiol alone decreases but estradiol supplemented together with progesterone increases 5HT1A mRNA expression in the hippocampus. Estradiol decreases the 5HT2C receptor gene expression, while estradiol in combination with progesterone increases the 5HT2A mRNA expression in the ventral hippocampus. Thus, estradiol alone has opposite effects compared to the estradiol/progesterone combination. To detect if acute tolerance develops to allopregnanolone, an EEG method was used where male rats by continuous allopregnanolone infusion were kept on anesthesia level of the silent second (SS). After different time intervals (first SS, 30 min or 90 min of anesthesia) several GABAA receptor subunit mRNAs were measured for detecting if changed expression of any GABAA receptor subunits is involved in development of acute tolerance. There is development of acute tolerance to allopregnanolone and brain regions of importance are hippocampus, thalamus and hypothalamus. The GABAA receptor alpha4 subunit in thalamus and alpha2 subunit in the dorsal hippocampus are related to development of acute tolerance. For assessing allopregnanolone behavioral effects, we studied how this neurosteroid affects spatial learning in the Morris water maze task Allopregnanolone inhibits spatial learning short after the injection and shows a specific behavioral pattern with swimming close to the pool wall. The steroid UC1011 can inhibit the increase in chloride ion uptake induced by allopregnanolone. UC1011 decreases allopregnanoloneinduced impairment of spatial learning in the water maze, as well as the specific behavioral swim pattern. In conclusion, the present work demonstrates that neuroactive steroids affect the 5HT and GABA systems in a brain region specific way. GABAA receptor subunit changes in hippocampus and thalamus are related to acute allopregnanolone tolerance. Allopregnanolone induces cognitive deficits, like spatial learning impairment and UC1011 can inhibit allopregnanolone-induced effects in vitro and in vivo. Key words: Estradiol, progesterone, HRT, allopregnanolone, UC1011, serotonin receptor, GABAA receptor, mRNA, Morris water maze, silent second, tolerance.
10

Sex and stress steroid modulation of GABA mediated chloride ion flux in rat CNS

Strömberg, Jessica January 2007 (has links)
Background: Sex and stress steroids are metabolized to 3a-hydroxy-pregnane-steroid metabolites such as allopregnanolone (Allo) and tetrahydrodeoxycorticosterone (THDOC). Allo and THDOC are neuroactive steroids that are metabolized in the brain and act in brain as potent positive GABAA receptor function modulators. Allo as well as THDOC levels increase during stress. Allo has been associated with a number of symptoms and malfunctions such as impaired memory function and negative mood symptoms in a subgroup of individuals both for animals and humans. Pregnane steroids with 3b-hydroxy-configuration (3b-steroids) have been shown to reduce the Allo enhanced GABA effect. Aims: The aims for the present thesis were to investigate the effect of 3b-steroids on the GABA mediated GABAA receptor function in presence of positive GABAA receptor modulators. Further, the regional variances between the 3b-steroids as well as the mechanism of the effect were studied. Finally, the effect of stress steroid metabolites on the GABAA receptor function was investigated. Results: 3b-OH-5a-pregnane-20-one reduced the Allo enhanced GABA mediated chloride ion uptake into cortical microsacs. The 3b-isomer reduced the efficacy of Allo without shift the concentration response curve. It is therefore suggested that the 3b-isomer has a non-competitive effect. Further, it was shown that the 3b-isomer reduced the Allo effect in a selective way since the 3b-isomer did not interact with other positive modulators or with GABA itself. Five tested 3b-steroids reduced the Allo enhanced GABA mediated chloride ion uptake in cerebral cortex and hippocampus as well as the Allo prolongation on spontaneous inhibitory postsynaptic currents (sIPSCs) in preoptic nucleus. In cerebellum on the other hand the 3b-steroids showed to have weaker or no effect compared to the other tested regions. Interestingly, in absence of Allo, two of the 3b-steroids positively modulated the GABA stimulated GABAA receptor function. In absence of Allo, 5b-pregnane-3b,20(R)-diol increased the desensitization rate of current response. In contrast to the reducing effect on the Allo induced prolongation on sIPSCs, the effect of the 3b-steroid on GABA application, was not altered in presence of Allo. The mechanism of the 3b-steroid is therefore suggested being desensitization dependent in contrast to Allo, which has been suggested to decrease the GABA unbinding rate. In contrast to the enhanced effect of Allo, glucocorticoid metabolites reduced the GABA mediated chloride ion uptake in a concentration dependent way. The results in present thesis indicate that both sex and stress steroid metabolites interact with the GABAA receptor function. The knowledge that diversity of endogenous steroids interact with the GABAA receptor function is of importance for further understanding of different sex and stress steroid related symptoms and syndromes.

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