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Kynurenate treatment of autaptic hippocampal microcultures affect localized voltage-dependent calcium diffusion in the dendrites

Padmashri, Ragunathan and Ganguly, Archan and Mondal, Partha Pratim and Rajan, K and Sikdar, Sujit Kumar (2006) Kynurenate treatment of autaptic hippocampal microcultures affect localized voltage-dependent calcium diffusion in the dendrites. In: Cell Calcium, 39 (3). pp. 247-258.

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Abstract

It is not clear how different spatial compartments in the neuron are affected during epileptiform activity. In the present study we have examined the spatial and temporal profiles of depolarization induced changes in the intracellular $Ca^2^+$ concentration in the dendrites of cultured autaptic hippocampal pyramidal neurons rendered epileptic experimentally by treatment with kynurenate (2 mM) and $Mg^2^+$ (11.3 mM) in culture (treated neurons). This was examined with simultaneous somatic patch-pipette recording and $Ca^2^+$ imaging experiments using the $Ca^2^+$ indicator Oregon Green 488 BAPTA-1. Neurons stimulated by depolarization under whole-cell voltage clamp conditions revealed $Ca^2^+$ entry at localized sites in the dendrites. $Ca^2^+$ transients were observed even in the presence of NMDA and AMPA receptor antagonists suggesting that the opening of voltage gated calcium channels primarily triggered the local $Ca^2^+$ changes. Peak $Ca^2^+$ transients in the dendrites of treated neurons were larger compared to the signals recorded from the control neurons. Dendritic $Ca^2^+$ transients in treated neurons showed a distance dependent scaling. Estimation of dendritic local $Ca^2^+$ diffusion coefficients indicated higher values in the treated neurons and a higher availability of free $Ca^2^+$. Simulation studies of $Ca^2^+$ dynamics in these localized dendritic compartments indicate that local $Ca^2^+$ buffering and removal mechanisms may be affected in treated neurons. Our studies indicate that small dendritic compartments are rendered more vulnerable to changes in intracellular $Ca^2^+$ following induction of epileptiform activity. This can have important cellular consequences including local membrane excitability through mechanisms that remain to be elucidated.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to Elsevier.
Keywords: Autaptic hippocampal neurons;Calcium imaging;Epilepsy;Dendrites;Calcium dynamics;Calcium diffusion coefficients
Department/Centre: Division of Biological Sciences > Molecular Biophysics Unit
Division of Physical & Mathematical Sciences > Physics
Date Deposited: 05 Feb 2007
Last Modified: 19 Sep 2010 04:28
URI: http://eprints.iisc.ernet.in/id/eprint/7205

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