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Expression and function of serotonin receptor isoforms in the respiratory system

dc.contributor.advisorRichter, Diethelm Prof. Dr.de
dc.contributor.authorManzke, Till PD Dr. Dr.de
dc.date.accessioned2012-04-16T14:57:00Zde
dc.date.available2013-01-30T23:50:40Zde
dc.date.issued2005-02-09de
dc.identifier.urihttp://hdl.handle.net/11858/00-1735-0000-0006-AC76-Ade
dc.identifier.urihttp://dx.doi.org/10.53846/goediss-661
dc.description.abstractEine Vielzahl unterschiedlicher Serotoninrezeptoren moduliert die neuronale Netzwerkaktivität mittels G-Protein aktivierter Signaltransduktionswege. Spezifische poly- und monoklonale Antikörper gegen die 5-HT2B, 5-HT4(a) und 5-HT7 Rezeptoren wurden generiert, um deren Verteilung im respiratorischen System zu untersuchen. Es konnte gezeigt werden, daß alle Rezeptoren im sog. PreBötzinger Komplex (PBC), der essentiell für die Rhythmogenese ist, exprimiert werden. Immunhisto-chemische und Einzelzell RT-PCR Analysen zeigten, daß die 5-HT4(a) und µ-Opioid Rezeptoren im PBC in respiratorischen Neuronen ko-exprimiert werden und möglicherweise über konvergierende Singalwege antagonistisch die intrazelluläre cAMP Konzentration regulieren. In-vivo Experimente zeigten, daß die systemische Applikation von BIMU-8 [5-HT4(a)R-Agonist] die respiratorische Aktivität steigert und Opioid-induzierte Atemdepression ohne Verlust der Analgesie kompensiert werden kann. Der Erhalt der Analgesie läßt sich anhand der fehlenden Expression des 5-HT4(a)R in Neuronen des Hinterhorns erklären. Weiterhin konnte gezeigt werden, daß die 5-HT1A, 5-HT7 und µ-Opioid Rezeptoren im PBC ko-exprimiert werden und ebenfalls mittels 8-OH-DPAT (Agonist für 5-HT1A und 5-HT7Rs) Opioid-induzierte Atemdepression kompensiert werden kann ohne Verlust der analgetischen Wirkung der Opioide. Die exzitatorische Wirkung von 8-OH-DPAT konnte dabei auf die Aktivierung des 5-HT1AR zurückgeführt werden. Da die 5-HT1A und µ-Opioid Rezeptoren die intrazelluläre cAMP Konzentration senken und der 5-HT7R keine systemische Wirkung zeigte, ist die Wirkung von 8-OH-DPAT auf einen komplexeren Netzwerkeffekt zurückzuführen. Anhand von RT-PCR und immunhistochemischen Analysen konnte ebenfalls gezeigt werden, daß auch die 5-HT2A und 2B Rezeptoren im PBC ko-exprimiert sind, welche über ein Gq-Protein die Phospholipase C aktivieren. Selektive Aktivierung des 5-HT2AR mittels a-methyl-5-HT bewirkte lediglich eine transiente respiratorische Depression und eine persistierende Hypotonie. Di e Injektion des 5-HT2BR-Agonisten (BW 723C86) und Antagonisten (LY 272015) zeigte keine Effekte. Obwohl alle untersuchten 5-HTRs im respiratorischen System exprimiert werden, konnte eine Opioid-induzierte Atemdepression ohne Verlust der Analgesie nur durch selektive Aktivierung der 5-HT1A und 4(a) Rezeptoren kompensiert werden, welches möglicherweise neue Strategien ermöglicht, kritischen klinischen Situationen einer Opioidtherapie entgegenzuwirken.de
dc.format.mimetypeapplication/pdfde
dc.language.isoengde
dc.rights.urihttp://webdoc.sub.gwdg.de/diss/copyr_diss.htmlde
dc.titleExpression and function of serotonin receptor isoforms in the respiratory systemde
dc.typedoctoralThesisde
dc.title.translatedExpression und Funktion von Serotoninrezeptorisoformen im respiratorischen Systemde
dc.contributor.refereeRichter, Diethelm Prof. Dr.de
dc.date.examination2005-01-24de
dc.subject.dnb570 Biowissenschaften, Biologiede
dc.description.abstractengA variety of different serotonin receptors (5-HTRs) are known to modify neuronal net-work activity through G-protein activated second messenger pathways. To obtain more information about the distribution of the 5-HT2B, 5-HT4(a), and 5-HT7 receptors within the respiratory network, specific poly- and monoclonal antibodies were produced. These specific antibodies revealed that all receptors were expressed in the pre-Bötzinger complex that represents an important part of the respiratory network essential for respiratory rhythm generation. The 5-HT4(a)R was strongly co-expressed with the µ-opioid receptor (µ-OR) in respiratory neurones of the PBC shown by immunohistochemistry and single-cell RT-PCR analysis. These data provided evidence for a convergent signal transduction pathway of both receptors which stimulate (5-HT4(a)R) or inhibit (µ-OR) the activity of the adenylyl cyclase. The physiological relevance was tested in a fully intact animal model. Systemic application of the 5-HT4(a)R-agonist BIMU-8 produced a significantly increased respiratory activity and even recovered opioid-induced respiratory depression, while the opioid-induced analgesia remained unaffected. The continuity of analgesia based on the fact that neurones of the dorsal horn, responsible for spinal inhibition of nociception on spinal cord level, did not express the 5-HT4(a)R, while the µ-OR was abundantly expressed. These findings demonstrate clinical relevance of selective 5-HT4(a)R activation in the treatment or protection against respiratory failure without loss of the anti-nociceptive effect of opioids. The 5-HT1AR was strongly co-expressed with the 5-HT7 and µ-opioid receptors in the PBC. The effects on breathing pattern of the 5-HT1A and 5-HT7 receptor agonist 8-OH-DPAT was also analysed in-vivo. Both receptor isoforms as well converge on the signalling cascade of µ-ORs, and systemic application of 8-OH-DPAT increased respiratory activity. The pharmacologically evoked excitatory effect was due to 5-HT1AR activation, because WAY 100635, a s pecific antagonist for the 5-HT1AR, blocked this effect, while SB 269970, a specific antagonist for the 5-HT7R, had no effects. Interestingly, opioid-induced depression of respiratory activity was success-fully recovered by subsequent application of 8-OH-DPAT without affecting analgesia. A secondary effect of 8-OH-DPAT on Gs-coupled 5-HT7 receptors can be largely excluded. However, 5-HT1A receptors utilise the identical signalling cascade inhibiting the adenylyl cyclase like µ-OR and thus, the rescue phenomenon is hardly to explain with a simple molecular mechanism. The 5-HT2A and 5-HT2B receptor isoforms were strongly co-expressed in neurones of the PBC shown by immunohistochemistry and RT-PCR analysis. Both receptor isoforms utilise a Gq-mediated signalling cascade leading to activation of phospholipase C and IP3/DAG pathways. This signal trans-duction pathway predicts an excitatory action of agonists for both receptors on respiration as has previously been verified on cellular level in earlier studies. Systemic application of the 5-HT2AR-agonist a-methyl-5-HT caused only a transient respiratory depression. This depression was accompanied by a pronounced increase in mean arterial pressure (MAP). The respiratory activity recovered, while MAP remained depressed and a hypotonia persisted. Injection of both the 5-HT2BR-agonist BW 723C86 and the antagonist LY 272015 caused neither transient nor longer lasting changes of breathing and MAP. All attempts to recover opioid-induced respiratory depression failed. These findings suggest that systemic activation of 5-HT2A or 5-HT2B receptors does not exert an excitatory effect on breathing. Taken together, although all serotonin receptors analysed are expressed in the respiratory system, only systemic activation of the serotonin 1A and 4 receptor isoforms restored potentially opioid-induced respiratory depression without loss of analgesia. This might open novel strategies for an effective treatment of critical clinical situations caused by opioid treatment.de
dc.contributor.coRefereeNeher, Erwin Prof. Dr.de
dc.contributor.thirdRefereeKnepel, Willhart Prof. Dr.de
dc.subject.topicMathematics and Computer Sciencede
dc.subject.gerSerotoninde
dc.subject.gerOpioidede
dc.subject.gerAtmungde
dc.subject.gerNetzwerkde
dc.subject.gerAntikörperde
dc.subject.engserotoninde
dc.subject.engopioidsde
dc.subject.engrespirationde
dc.subject.engnetworkde
dc.subject.engantibodiesde
dc.subject.bk42.17 Allgemeine Physiologiede
dc.identifier.urnurn:nbn:de:gbv:7-webdoc-94-4de
dc.identifier.purlwebdoc-94de
dc.affiliation.instituteBiologische Fakultät inkl. Psychologiede
dc.subject.gokfullWIde
dc.identifier.ppn487792874de


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