Neuroscience 2004 Abstract
| Presentation Number: | 849.15 |
|---|---|
| Abstract Title: | Excitation-induced calcium influx in a normal myelinated axon lacks spatial heterogeneity. |
| Authors: |
Zhang, C. L.*1
; Chang, J.1
; Chiu, S. Y.1
1Dept. of Physiology, Univercity of Wisconsin Madison, Madison, WI |
| Primary Theme and Topics |
Synaptic Transmission and Excitability - Ion Channels -- Calcium Channels: Physiology |
| Session: |
849. Calcium Channels: L and Other Poster |
| Presentation Time: | Wednesday, October 27, 2004 10:00 AM-11:00 AM |
| Location: | San Diego Convention Center - Hall A-H, Board # K23 |
| Keywords: | calcium channel, mouse optic nerve, myelinated axon, photolysis |
The myelin sheath enables saltatory conduction by demarcating the axon into a small nodal region for excitation and an extended, insulated internodal region for efficient spread of passive current. This anatomical demarcation produces a dramatic heterogeneity in ionic fluxes during excitation, a classical example being the restriction of Na influx at the node. However, ionic fluxes are not restricted only to Na during excitation, as recent studies have revealed that action potentials also induce calcium influx into axons of mammalian optic nerves. Does calcium influx along a myelinated axon also show spatial heterogeneity during excitation, as in the case for sodium? To address this, we analyzed spatial profiles of axonal calcium transients during excitation by selectively staining axons with calcium indicators, and analyze the data by two models, one assuming uniform axonal influx and the other assuming discrete nodal influx, with a coefficient of axial calcium diffusion empirically determined in situ using photolysis of caged compounds. The results show surprisingly that internodal calcium influx, and but not nodal influx, accounts for virtually all the axonal calcium transients in a myelinated fiber during normal action potentials.
Supported by This study is supported by grants RO1-23375 from National Institutes of Health and RG-3247-A-6 from the National Multiple Sclerosis Society underwritten by the Estate of Norman Cohn
Sample Citation:
[Authors]. [Abstract Title]. Program No. XXX.XX. 2004 Neuroscience Meeting Planner. San Diego, CA: Society for Neuroscience, 2004. Online.
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