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Epileptiform activity induces distance-dependent alterations of the $Ca^{2+}$ extrusion mechanism in the apical dendrites of subicular pyramidal neurons

Srinivas, Kalyan V and Sikdar, Sujit Kumar (2008) Epileptiform activity induces distance-dependent alterations of the $Ca^{2+}$ extrusion mechanism in the apical dendrites of subicular pyramidal neurons. In: European Journal Of Neuroscience, 28 (11). pp. 2195-2212.

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Official URL: http://www3.interscience.wiley.com/journal/1215063...

Abstract

The cellular and molecular mechanisms that underlie acquired changes in Ca2+ dynamics of different neuronal compartments are important in the induction and maintenance of epileptiform activity. Simultaneous electrophysiology and Ca2+ imaging techniques were used to understand the basic properties of dendritic Ca2+ signaling in rat subicular pyramidal neurons during epileptiform activity. Distance-dependent changes in the Ca2+ decay kinetics locked to spontaneous epileptiform discharges and back-propagating action potentials were observed in the apical dendrites. A decrement in the mean tau value of Ca2+ decay was observed in distal parts (95-110 mu m) of the apical dendrites compared with proximal segments (30-45 mu m) in in-vitro epileptic conditions but not in control. Pharmacological agents that block Ca2+ transporters, i.e. Na+/ Ca2+ exchangers (Benzamil), plasma membrane Ca2+-ATPase pumps (Calmidazolium) and smooth endoplasmic reticulum Ca2+-ATPase pumps (Thapsigargin), were applied locally to the proximal and distal part of the apical dendrites in both experimental conditions to understand the molecular aspects of the Ca2+ extrusion mechanisms. The relative contribution of Na+/Ca2+ exchangers in Ca2+ extrusion was higher in the distal apical dendrites in the in-vitro epileptic condition and this property modulated the excitability of the neuron in simulation. The Ca2+ homeostatic mechanisms that restore normal Ca2+ levels could play a major neuroprotective role in the distal dendrites that receive synaptic inputs.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to World Scientific Publishing Company.
Keywords: Ca2+ extrusion;Ca2+ imaging;epileptiform activity;Na+/Ca2+ exchangers;rat;subiculum.
Department/Centre: Division of Biological Sciences > Molecular Biophysics Unit
Date Deposited: 01 May 2009 03:31
Last Modified: 01 May 2009 03:31
URI: http://eprints.iisc.ernet.in/id/eprint/17683

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