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Differential dendritic Ca 2+ signalling in young and mature hippocampal granule cells
Author(s) -
Stocca Gabriella,
SchmidtHieber Christoph,
Bischofberger Josef
Publication year - 2008
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2008.155739
Subject(s) - hippocampal formation , granule (geology) , chemistry , neuroscience , microbiology and biotechnology , biophysics , biology , paleontology
Neuronal activity is critically important for development and plasticity of dendrites, axons and synaptic connections. Although Ca 2+ is an important signal molecule for these processes, not much is known about the regulation of the dendritic Ca 2+ concentration in developing neurons. Here we used confocal Ca 2+ imaging to investigate dendritic Ca 2+ 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 Ca 2+ ‐sensitive fluorescent dye OGB‐5N, we found that both young and mature granule cells showed large action‐potential evoked dendritic Ca 2+ transients with similar amplitude of ∼200 n m , indicating active backpropagation of action potentials. However, the decay of the dendritic Ca 2+ 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 Ca 2+ signals during theta‐frequency stimulation in the young neurons. Comparison of the peak Ca 2+ concentration and the decay measured with different Ca 2+ indicators (OGB‐5N, OGB‐1) in the two populations of neurons revealed that the young cells had an ∼3 times smaller endogenous Ca 2+ ‐binding ratio (∼75 versus ∼220) and an ∼10 times slower Ca 2+ extrusion rate (∼170 s −1 versus ∼1800 s −1 ). These data suggest that the large dendritic Ca 2+ 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.