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Institut für Biologie

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Browsing Institut für Biologie by Subject "Agonist"

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    Neuronale Modulation : der Einfluss von Agonisten und inverser Agonisten auf das Cannabinoidsystem einer hippocampalen Primärkultur
    (2007) Klink, Oliver; Hanke, Wolfgang
    The aim of this thesis was to investigate the effect of inverse agonists on the CB1-receptor with an established complex neuronal-/ glia- co culture obtained from hippocampi of embryonic rats. To provide evidence of the expression of the CB1-receptors in the established culture immunocytochemical studies have been used and showed a sufficient expression level of the CB1-receptors. The neuronal culture was further tested on various electrophysiological parameters to verify an in vitro assay that resembles in vivo characteristics. Thus the exposure of TTX to neurons lead to reduced spike activity which refers to the blocking of voltage gated sodium channels. Also the inhibition of AMPA receptors using CNQX showed a reduction of spike activity in respect of the reduced synaptic activity. Analyses of the kinetic and spike frequencies of the generated actionpotentials as well as the kinetics and frequencies of spontaneous AMPA- and NMDA epscs are to a large extent comparable to published data of in vitro and in vivo assays. To reduce the intrinsic variability of the established cannabinoid assay the method of induced burst activity under low magnesium conditions has been used. This method results indeed in a lower variability of the assay but also the analysis of the effect of cannabinoid agonists and inverse agonists on the evoked burst activity showed interesting inverse modulations of burst durations, event intervals and inter-event intervals compared to alterations of the spike frequencies. On the basis of the obtained data by the analyzed spike-frequencies an agonistic effect of nanomolar concentrations of the investigated inverse agonists could be shown for the first time. This observation could lead to the conclusion that this might be a specific interaction of the investigated inverse agonist with an other receptor. The inhibition of the adenylatcyclase, a key-enzyme of the CB1 signal transduction, neutralizes the agonistic effect, although the inverse agonistic effect dissapeard. In addition the interaction of the opioid system in respect to the observed agonistic effect of rimonabant has been investigated. However, non of the published interaction of this two systems in respect to the agonistic effect of rimonabant could be observed.