Initiation and propagation of a neuronal intracellular calcium wave |
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Authors: | Bradford E Peercy |
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Institution: | (1) Laboratory of Biological Modeling/NIDDK/NIH, Bldg. 12A, Rm 4007, MSC 5621, South Dr., Bethesda, MD 20892-5621, USA |
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Abstract: | The ability to image calcium movement within individual neurons inspires questions of functionality including whether calcium
entry into the nucleus is related to genetic regulation for phenomena such as long term potentiation. Calcium waves have been
initiated in hippocampal pyramidal cells with glutmatergic signals both in the presence and absence of back propagating action
potentials (BPAPs). The dendritic sites of initiation of these calcium waves within about 100 μm of the soma are thought to
be localized near oblique junctions. Stimulation of synapses on oblique dendrites leads to production of inositol 1,4,5-trisphosphate
(IP3) which diffuses to the apical dendrite igniting awaiting IP3 receptors (IP3Rs) and initiating and propagating catalytic calcium release from the endoplasmic reticulum. We construct a reduced mathematical
system which accounts for calcium wave initiation and propagation due to elevated IP3. Inhomogeneity in IP3 distribution is responsible for calcium wave initiation versus subthreshold or spatially uniform suprathreshold activation.
However, the likelihood that a calcium wave is initiated does not necessarily increase with more calcium entering from BPAPs.
For low transient synaptic stimuli, timing between IP3 generation and BPAPs is critical for calcium wave initiation. We also show that inhomogeneity in IP3R density can account for calcium wave directionality. Simulating somatic muscarinic receptor production of IP3, we can account for the critical difference between calcium wave entry into the soma and failure to do so. |
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Keywords: | Evanescent calcium wave Calcium signaling Mathematical model Hippocampal CA1 pyramidal cell |
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