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This Article Full Text Full Text (PDF) All Versions of this Article: 586/16/3795    most recent jphysiol.2008.155739v2 jphysiol.2008.155739v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Stocca, G. Articles by Bischofberger, J. PubMed PubMed Citation Articles by Stocca, G. Articles by Bischofberger, J. Related Collections Neuroscience

¹ Physiological Institute 1, University of Freiburg, Hermann-Herder-Strasse 7, D-79104 Freiburg, Germany

Neuronal activity is critically important for development and plasticity of dendrites, axons and synaptic connections. Although Ca²⁺ is an important signal molecule for these processes, not much is known about the regulation of the dendritic Ca²⁺ concentration in developing neurons. Here we used confocal Ca²⁺ imaging to investigate dendritic Ca²⁺ signalling in young and mature hippocampal granule cells, identified by the expression of the immature neuronal marker polysialated neural cell adhesion molecule (PSA-NCAM). Using the Ca²⁺-sensitive fluorescent dye OGB-5N, we found that both young and mature granule cells showed large action-potential evoked dendritic Ca²⁺ transients with similar amplitude of 200 nM, indicating active backpropagation of action potentials. However, the decay of the dendritic Ca²⁺ concentration back to baseline values was substantially different with a decay time constant of 550 ms in young versus 130 ms in mature cells, leading to a more efficient temporal summation of Ca²⁺ signals during theta-frequency stimulation in the young neurons. Comparison of the peak Ca²⁺ concentration and the decay measured with different Ca²⁺ indicators (OGB-5N, OGB-1) in the two populations of neurons revealed that the young cells had an 3 times smaller endogenous Ca²⁺-binding ratio (75 versus 220) and an 10 times slower Ca²⁺ extrusion rate (170 s^–1 versus 1800 s^–1). These data suggest that the large dendritic Ca²⁺ signals due to low buffer capacity and slow extrusion rates in young granule cells may contribute to the activity-dependent growth and plasticity of dendrites and new synaptic connections. This will finally support differentiation and integration of young neurons into the hippocampal network.

(Received 22 April 2008; accepted after revision 25 June 2008; first published online 26 June 2008)
Corresponding author J. Bischofberger: Physiologisches Institut, Universitat Freiburg, Hermann-Herder-Str. 7, D-79104 Freiburg, Germany. Email: josef.bischofberger{at}uni-freiburg.de