| 1. |
- Granholm, Linnea
(författare)
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Neurobiological Consequences of Social Conditions and Alcohol Exposure in Adolescent rats
- 2015
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Adolescence represents a time of extensive reorganisation and maturation of brain circuits involved in emotions, motivation and cognition and it is a period particular sensitive for external stimuli. External stimuli can be both socio-environmental factors and exposure to exogenous compounds such as drugs of abuse (e.g. alcohol). If these stimuli are of an adverse nature the probability of develop neuropsychiatric diseases or addiction is increased. To study the neurobiological consequences of adverse events during adolescence animal models are crucial since they give the opportunity of providing an environment where the exposure of the stimuli is controlled and also enable a detailed analysis of the effects in the brain. The overall aim of in this thesis was to investigate how environmental factors, social conditions or alcohol exposure, during adolescence affect the brain and/or drug-taking in rats. Rats are very sensitive for dis- turbances in their social conditions and to induce an adverse social environment, early adolescent rats where single-housed for either a short or prolonged time. A short period of single housing induced an acute stress response and increased levels of nociceptin/orphanin FQ in brain areas associated with stress. Prolonged single housing reduced the levels of Met-enkephalin-Arg6Phe7 in several brain areas. Rats exposed to alcohol during adolescence had an altered dopamine response in dorsal striatum after an am- phetamine challenge but displayed similar amphetamine intake-behaviour as water controls. However, animals exposed to a combination of adolescent alcohol exposure and subsequent amphetamine intake had a more efficient removal of dopamine in dorsal striatum after an amphetamine challenge. This thesis demonstrates how two different environmental stimuli are able to alter the neurobiology in adolescent rats. The results further support the notion that environmental conditions are of importance for normal brain maturation and provide new evidence that endogenous opioids are severely affected by social dis- turbances during adolescence. Furthermore, additional information is provided to the existing literature of how alcohol exposure during adolescence affects dopamine dynamics and drug-taking behaviour. In the literature, the majority of the studies of adolescent alcohol exposure have focused on the nucleus accum- bens, a brain area important in the processing of rewards. The results herein provide evidence that dorsal striatum, a brain area involved in the transition into habitual drug use is also affected by adolescent alco- hol exposure. An altered drug response in dorsal striatum may affect habit formation and contribute to a heightened susceptibility for high drug consumption later in life.
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| 2. |
- Lundberg, Stina
(författare)
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Examining Female Resilience to Early Environmental Influences : Short- and long-term consequences on behaviour, HPA axis activity and alcohol intake after prolonged maternal separation
- 2017
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Early-life experiences are an important factor influencing further development of the individual. Adverse experiences early in life, such as various kinds of abuse or neglect, are types of early-life stress that can adversely affect an individuals health, as well as contribute to the development of an array of disorders later in life. Most prominent is the increased risk for psychiatric disorders, primarily depression, anxiety-related and substance use disorders. Many of the implicated disorders also exhibit sex-dependent differences in prevalence and severity. Thus, it is important to consider sex-dependent effects when modeling early-life stress and its consequences. A common animal model for early-life stress is prolonged maternal separation (MS). MS is an umbrella term for different manipulations of the early environment of rodent pups. In this thesis, a prolonged MS condition with separation of rat litters from their dams for six hours per day during the first three weeks of life (MS360) was used. In male offspring MS360 have been associated with early-life stress and negative effects apparent during both adolescence and adulthood. The literature regarding female offspring is not as substantial as for the males, but it seems that females’ exhibit less pronounced or no effect after prolonged MS independent of separation time. In addition, the studies that have examined female offspring have done so in adulthood and thus, short-term consequences of prolonged MS possibly present during adolescence have not been investigated. The aim of this thesis is to provide a broad investigation into the consequences of prolonged MS in female offspring, in both adolescence and adulthood. As stated above, MS360 was used as the adverse rearing condition in this thesis. As control, daily short MS (15 min; MS15) was used; this ensured that all animals were handled equally, except for the length of separation. Any detected differences are thus due to the length of separation only. Three categories of assessments were used to evaluate short- and long-term consequences: 1) hypothalamus-pituitary-adrenal (HPA) axis assessments, 2) behavioral assessments and 3) assessment of voluntary alcohol consumption. HPA axis reactivity was assessed in adolescent and adult offspring by blood sampling before and after challenge. HPA activity was also evaluated after long-term alcohol consumption by measurement of the fecal corticosterone content. Behavior was assessed in adolescence by registration of social play behavior and in adulthood by generation of behavioral profiles in the multivariate concentric square fieldTM (MCSF). Alcohol consumption was evaluated using the modified intermittent alcohol access schedule with the two- (20% alcohol) and three- bottle (5% and 20% alcohol) free-choice paradigms. Female offspring did not differ depending on rearing condition in HPA reactivity in adolescence or adulthood. However, after the long-term alcohol intake, MS360 females had increased levels of corticosterone in their feces compared to MS15 females. No difference was detected in adolescent social play among female offspring and only a minor alteration was detected in the adult behavioral profile, where MS360 females had increased risk assessment compared to MS15 females. No effect of rearing condition was seen during the two-bottle choice paradigm of alcohol intake, while whole- group differences over time were discovered. Alcohol intake and preference were highest the first week of access and directly after a two-week deprivation period, apart from those time-points, intake and preference were maintained on a stable level. In the three-bottle choice, an interaction with rearing condition was revealed for the total alcohol preference, however this only translated to a minor group-dependent difference. In conclusion, females reared under a prolonged MS paradigm exhibited no or only minor basal changes in HPA axis reactivity, behavior and alcohol consumption. However, after long-term alcohol intake females subjected to prolonged MS had increased corticosterone excretion into feces. That differences only emerge after long-term perturbation can be a sign that females have higher buffering capabilities than males after early-life adversity, as modeled through prolonged MS, and thus require additional challenges before consequences become apparent. This thesis highlights the importance of considering sex when studying the impact of early-life stress, and that the choice of animal model needs to be considered carefully in relation to the research question posed.
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| 3. |
- Zayny, Ahmad
(författare)
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Vitamin D metabolism in osteoblast-like cells : effects of drugs on inactivation by CYP24A1
- 2018
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Vitamin D is essential for bone function, and deficiency in active vitamin D hormone can lead to bone disorders. Long-term treatment with glucocorticoids and antiretroviral drugs used to treat HIV infection, results in osteoporosis and increased risk of fractures. Much remains unclear regarding the effects of these compounds in bone cells. In the current study, human osteosarcoma Saos-2 cells and primary human osteoblasts were found to express mRNA for the vitamin D receptor as well as activating and deactivating enzymes in vitamin D3 metabolism. These bone cells exhibited CYP24A1-mediated 24-hydroxylation, involved in deactivation of the active vitamin form. However, bioactivating vitamin D3 hydroxylase activities were not detected in either of these cells, indicating that local vitamin D bioactivation is not significant in osteoblasts.Several glucocorticoids and antiretroviral drugs, including prednisolone, efavirenz and ritonavir, down regulated CYP24A1 mRNA expression. Prednisolone and ritonavir also down regulated CYP24A1-mediated 24-hydroxylase activity in both Saos-2 and primary human osteoblasts.Also, prednisolone significantly suppressed a human CYP24A1 promoter-luciferase reporter gene in Saos-2 cells co-transfected with the glucocorticoid receptor. Thus, the results of the present study show suppression by glucocorticoids on CYP24A1 mRNA, CYP24A1-mediated metabolism and CYP24A1 promoter activity in human osteoblast-like cells. Interestingly, ritonavir markedly potentiated the induction of CYP24A1 mRNA expression by 1,25-dihydroxyvitamin D3 suggesting that ritonavir may have different regulatory effects depending on the vitamin D3 metabolite levelsAs part of this study, we examined if glucocorticoids are formed locally in Saos-2 cells. The experiments indicate formation of 11-deoxycortisol, a steroid with glucocorticoid activity, which can bind the glucocorticoid receptor. Our findings showing effects of glucocorticoids and antiretroviral drugs on CYP24A1 expression in human osteoblasts indicate a previously unknown mechanism for effects of glucocorticoids and antiretroviral drugs in human bone, where effects of these drugs may lead to altered levels of active vitamin D3.
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