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Modulation of calcium wave propagation in the dendrites and to the soma of rat hippocampal pyramidal neurons
Author(s) -
Watanabe Shigeo,
Hong Min,
LasserRoss Nechama,
Ross William N.
Publication year - 2006
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.2006.114231
Subject(s) - soma , apical dendrite , dendritic spike , stimulation , neuroscience , hippocampal formation , chemistry , physics , biophysics , biology , excitatory postsynaptic potential , inhibitory postsynaptic potential
Repetitive synaptic stimulation in the stratum radiatum (SR) evokes large amplitude Ca 2+ waves in the thick apical dendrites of hippocampal CA1 pyramidal neurons. These waves are initiated by activation of metabotropic glutamate receptors (mGluRs), which mobilize inositol‐1,4,5‐trisphospate (IP 3 ) and release Ca 2+ from intracellular stores. We explored mechanisms that modulate the spatial properties of these waves. Higher stimulus current evoked waves of increasing spatial extent. Most waves did not propagate through the soma; the majority stopped close to the junction of the soma and apical dendrite. Pairing strong stimulation with one electrode and subthreshold stimulation with another (associative activation) extended the waves distally but failed to extend waves into the cell body. Pairing synaptic stimulation with backpropagating action potentials enhanced the likelihood of wave generation but did not extend the waves to the somatic region. Priming the stores with Ca 2+ entry through voltage dependent channels modulated wave properties but did not extend them past the dendrites. These results are consistent with propagation failing due to the dilution of synaptically generated IP 3 as it diffuses into the large volume of the soma (impedance mismatch). Synaptically activating waves in the presence of low concentrations of carbachol, which probably increased the tonic level of IP 3 throughout the cell, enhanced the extent of propagation and generated waves that invaded the soma, as long as low‐affinity indicators were used to detect the [Ca 2+ ] i changes. Consistent with this explanation direct injection of IP 3 into the soma promoted wave propagation into this region. Ca 2+ waves that propagated through the cell body were interesting because they did not fill the volume of the soma, but passed through the centre, often with large amplitude. These waves may be particularly effective in activating gene expression and protein synthesis.