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Title: Effect of H2O2 on the Delayed Rectifier Potassium Current in Dissociated Hippocampal CA1 Neurons
Authors: سونيا ماجد كاظم حسن 
Supervisor: د. وليد شعيب
Keywords: Rectifier Potassium Current Hippocampal CA1 Neurons
Issue Date: 2011
Publisher:  Kuwait university - college of graduate studies
Abstract: Hydrogen peroxide ( H2O2 ) is a reactive oxygen species that, when in excess, is known to cause oxidative damage to various biomolecules. The present study examined the effect of H2O2 on the delayed rectifier current ( IKDR ), a voltage – dependent current of paramount importance for neuronal excitability. Whole cell voltage – clamp experiments were performed on freshly dissociated hippocampal CA1 neurons of adult SD rats. The means were compared using Student's t-tests. One way ANOVA followed by Dunnett’s multiple comparison test were used when comparing multiple groups. Results obtained in the present study show that the external application of membrane permeable H2O2 for 6 minutes inhibited IKDR in a concentration dependent manner. H2O2 (600 μM) reduced IKDR’s amplitude and voltage – dependence albeit it accelerated IKDR activation. 1 mM Desferoxamine ( DFO ), an iron – chelator that prevents hydroxyl radical ( .OH ) generation, prevented H2O2 – induced reduction in IKDR , thus identifying .OH as the intermediate oxidant responsible for IKDR inhibition. Application of 600 μM sulfhydryl ( SH ) - oxidizing agent 5,5 – dithio-bis-nitrobenzoic acid ( DTNB ) for 6 minutes mimicked the effect of H2O2, whereas 2mM of the SH - reducing agents dithiothreitol ( DTT ) and 5mM glutathione ( GSH ) reversed and prevented the inhibition in IKDR respectively. These results identify SH groups of cysteine residues as an oxidative target on the KDR channel. However, while 2mM DTT completely reversed the inhibitory effect of DTNB, it only partially reversed the inhibitory effect of H2O2 suggesting another mechanism, in addition to SH oxidation, may exist for the reduction in IKDR by H2O2. Membrane impermeable oxidative and reducing agents had effects only when added intracellularly indicating .OH interacted with free SH groups of cysteine residues found in the intracellular aspect of the KDR channel protein. Oxidation of SH groups of intracellular cysteine residues by .OH resulted in the inhibition of v IKDR which would lead to changes in neuronal electrical excitability and may lead to neuronal death such as that observed in diseases associated with oxidative stress.
Appears in Programs:0530 Physiology (Ph.D.)

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