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Study of opioid receptors
Cechová, Kristína ; Hudeček, Jiří (advisor) ; Holáň, Vladimír (referee)
1 ABSTRACT In this Thesis, we studied properties of μ-, δ-, and κ-opioid receptors in lymphocytes isolated from rat spleen. This splenocytes were exposed to mitogen concanavalin A or opiate morphine and cultivated for 48 hours. Under physiological conditions, level of opioid receptors in immune cells is very low. Due to various factors such as presence of opioids, mitogens, long-term exposition to stress, expression of these receptors can be amplified. In this study we demonstrated, that concanavalin A causes up-regulation of μ-, δ- and κ-opioid receptors in lymphocytes isolated from rat spleen. In control cells no significant signal of μ- or δ-receptors was observed. In contrast, κ-opioid receptors were detected already in control cells. Concanavalin A stimulation caused a 2.4 - fold increase of these receptors. In lymphocytes treated with morphine only μ-opioid receptors were up-regulated, whereas in control cells, there was no signal for these receptor type. δ-opioid receptors were not detected in control or morphine treated cells. κ-opioid receptors were determined in control and also in morphine affected lymphocytes but the amount of these receptors wasn't changed by morphine. Detection of μ-, δ- and κ-opioid receptors using Western blot technique in lymphocytes isolated from rat spleen, that were...
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Modulatory effect of monovalent ions on δ-opioid receptors
Vošahlíková, Miroslava ; Svoboda, Petr (advisor) ; Jakubík, Jan (referee) ; Kršiak, Miloslav (referee)
The exact role of opioid receptors in drug addiction and modulatory mechanism of action of monovalent cations on these receptors are still not fully understood. Our results support the view that the mechanism of addiction to morphine is primarily based on desensitization of μ- and δ-opioid receptors. Desenzitization of agonist response proceeds already at the level of G protein functional activity. Long-term exposure of rats to morphine resulted in increase of number of δ-opioid receptors and change of their sensitivity to sodium ions. Analysis of the effect of different monovalent ions on agonist binding in δ-OR- Gi1α (Cys351 -Ile351 )-HEK293 cell line confirmed the preferential sensitivity of δ-opioid receptor to sodium ions. We have distinguished the high- and low-affinity Na+ sites. Biophysical analysis of interaction of lithium, sodium, potassium and cesium ions with plasma membranes isolated from HEK293 cells with the help of fluorescent probes indicated that monovalent ions interact, in low-affinity manner, with the polar, membrane-water interface of membrane bilayer. Key words: morphine, forebrain cortex, opioid receptors, G proteins, monovalent ions, plasma membrane, fluorescence spectroscopy.
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Changes in opioid signalisation during the ontogenesis.
Hoľuková, Martina ; Hejnová, Lucie (advisor) ; Škrabalová, Jitka (referee)
Opioid receptors interact with opiate compounds, causing the inhibition of neuroexcitability. The activation of signaling pathway of opioid receptors plays crucial role in the treatment of chronic and cancer pain. Summary of the general knowledge about opioid receptors and about the development of tolerance is in the first part of this work. Next part of the thesis concerns on ontogenesis of opioid receptors and other components related to the opioid signaling pathways as age seems to have an immense influence on molecules within and related to the opioid signaling. Finally, last part of this work collects data about the influence of morphine during ontogenesis as morphine is one of the most used opiate compound used in clinical treatment. Key words Opioid receptor, signalization, ontogenesis, addiction, tolerance, morphine
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Conformational states of the opiod receptors
Provazníková, Adéla ; Hudeček, Jiří (advisor) ; Entlicher, Gustav (referee)
This Thesis elucidates the relationships between structure and function of opioid receptors. The mechanism of opioid receptor function could be better understood on the basis of the recent knowledge of their three-dimensional structure. In the first part of the Thesis, methods for membrane protein crystallization and X-ray structural analysis are reviewed with a special focus on in meso crystallization. Next, the three opioid receptor subtype crystal structures are described and analysed, starting with their general architecture and proceeding to the detailed description including the binding pocket for opioid ligands with the help of visualization with the PyMol software. In its third part, this Thesis re-examines the structure-function correlations predicted on the basis of site-directed mutagenesis (Décaillot F.M. et al, Nature Structural Biology 10, 629, 2003) in the light of now available crystal structure. This analysis is pointing to the potentially important contacts of aspartate D128, suggesting that ligand binding and receptor activation might involve changes in its interaction with tyrosine Y308.
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Functional activity of opioid receptors in membrane domains
Cechová, Kristína ; Hudeček, Jiří (advisor) ; Mrízová, Iveta (referee)
7 ABSTRACT In this Thesis, we examined the influence of morphine administration to the laboratory rats on the amount of µ-opioid receptors and caveolins in their cerebral cortex. Effect of morphine is known to be caused by its binding to opiod receptors, in particular to the µ subtype, and a long-term exposure to morphine reduces the functionality and number of these receptors as part of the resulting tolerance and addiction. Caveolins are proteins essential for formation of the membrane microdomains of caveolae, although it is known today that presence of these proteins is not limited to caveolae and their function is probably independent of these domains (they may participate in the regulation of cell signaling pathways, lipid transport, etc.). The function of caveolins in brain cells is not precisely known yet. In the experimental part of this work, we used the Western blot method to estimate the presence of caveolin-1 and caveolin-2 in the cerebral cortex of the rats after ten-days morphine application and in control animals. A significant increase of caveolin-1 was observed after morphine treatment as compared to control animals; a smaller, non-significant increase of caveolin-2 was also found. The amount of μ-opioid receptors in morphine affected animals was significantly decreased compared to...
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Methadone Maintenance Treatment - The pharmacokinetics and the pharmacodynamics as a basis.
Pajorová, Júlia ; Hejnová, Lucie (advisor) ; Melkes, Barbora (referee)
The aim of this study was to summarize the pharmacokinetic and pharmacodynamic knowledge about methadone, and to compare it with morphine on both molecular and clinical level. Methadone and morphine are μ opioid agonists, and therefore their effect on the organism is similar. However, the existence of fundamental differences between them, is decisive for their use in clinical practice. It was discovered that on a molecular level, methadone has a higher efficiency to internalise μ receptors than morphine, moreover it's potential to form addiction and tolerance is lower. From a pharmacokinetic point of view, methadone in contrary to morphine has a much longer elimination half-life, which brings a lots of benefits and lots of disadvantages. One of the benefits is longer effect, which together with the lower potential for tolerance and addiction development, predetermined methadone to be used for maintenance therapy for patients addicted to opiates. Maintenance therapy is based on the replacement of an illegal drug (mainly heroine), for an opiate of similar nature, which on the other hand has more favourable effects on the patient (methadone). The purpose of it is to ease the development of withdrawal symptoms during therapy's first stages, and with gradual lowering of methadone dosage, to lead the...
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Effect of morphine on the resistance of the heart to ischemia
Mošovská, Linda ; Neckář, Jan (advisor) ; Žurmanová, Jitka (referee)
2. Abstract Opioids are considered as dangerous and addictive substances, mainly due to synthetic opioids such as heroin. It was discovered, that these substances can play an important role in myocardial ischemia because they can limit the damage of the heart tissue that occurs during a heart attack. Since that heart attack is the most common cardiovascular disease, the protective effect is significant. Cardioprotective effect is mainly mediated through δ opioid receptors, but the few studies have shown cardioprotective effect mediated through κ opioid receptors. The protective effect occurs by activation of opioid receptors by their agonists (eg. morphine or TAN-67), either before ischemia (opioid preconditioning) or before reperfusion (opioid postconditioning). The signaling pathway of cardioprotection include mitochondrial KATP channel, Gi/o proteins, protein kinase C, tyrosine kinases and reactive oxygen species.
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Importance of particular regions of CNS in the development of opioid addiction
Vyvadilová, Tereza ; Hejnová, Lucie (advisor) ; Roubalová, Lenka (referee)
Opiods are used as the most powerful painkillers in the medicine. The mechanism of their effect is determined by binding to the opioids receptors located in the central nervous system and peripheral nervous system. The opioids have high potential to develop addiction. Significance of psychical addiction belongs to losing control above using and compulsive desire to obtain drug of abuse to achieve certain psychical state. The somatic part is increase tolerance demonstrating need of dose increasing to achieve required effect. This thesis summarizes knowledge about particular regions of the central nervous system which participate on developing of addiction as ventral tegmental area, nucleus accumbens, locus coeruleus, ventral pallidum and amygdala. It seems that main role in developing of addiction acts the mesolimbic reward system which relates with increased release of dopamine resulting in stimulation of the brain reward system.
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Effect of chronic morphine treatment of rats on myocardial signaling systems regulated by trimeric G-proteins
Škrabalová, Jitka ; Novotný, Jiří (advisor) ; Rudajev, Vladimír (referee)
It has recently been discovered that the effect of morphine can significantly reduce the tissue damage that occurs during myocardial ischemia. The molecular mechanisms by which morphine acts on the heart are still little understood. The aim of this thesis was to monitor the effect of chronic 27-day and 10-day administration of low (1 mg/kg/day) and high (10 mg/kg/ day) doses of morphine on the expression of selected G-protein-coupled receptors (GPCR) and on the expression and activity of adenylyl cyclase (AC). Chronic (27 days) morphine treatment reduced the expression of к-opioids receptors, but 10-day morphine exposure did not influence the expression of these receptors. Assessment of β1- and β2-AR by immunoblot technique did not show any significant change in the expression, but the more accurate determination of β-AR expression using the saturation binding studies revealed that 27-day treatment with high doses of morphine appreciable increased the total number of these receptors. Administration of high doses of morphine led to marked up-regulation of adenylyl cyclase (AC) isoforms V/VI, and the amount of AC decreased proportionally with the time of discontinuation of morphine administration. Low doses of morphine up- regulated AC only during 27-day administration. Chronic morphine exposure did...
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Molecular physiology of opioid receptors
Valný, Martin ; Novotný, Jiří (advisor) ; Hejnová, Lucie (referee)
The opioid receptors (OR) belong to the family of G protein-coupled receptors (GPCRs). ORs mediate the effects of the opioids, leading primarily to inhibition of neuroexcitability, predominantly through the class of the inhibitory G proteins Gi/Go. Cloning of ORs confirmed the existence of four subtypes of ORs, which mediate effects of different classes of opioid ligands. The major aim of this work is to summarize the current knowledge about characteristics and function of ORs at the molecular level. Acute exposition of ORs to their agonists results in activation of the signaling cascades that trigger mechanisms leading to analgesia. Chronic exposition of ORs to their agonists leads to desensitization and internalization of the receptors and induces adaptive changes in signal transduction system that suppresses the opioid action, and may result in the development of opioid tolerance and dependence. Although a big progress has been made in the field of understanding the molecular mechanisms of the OR-mediated signaling, there are still a lot of unresolved questions that are necessary to answer.
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