Breakdown of accommodation in nerve: a possible role for persistent sodium current
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Breakdown of accommodation in nerve: a possible role for persistent sodium current Kristian Hennings*, Lars Arendt-Nielsen and Ole K Andersen Address: Center for Sensory-Motor Interaction (SMI), Aalborg University. Frederik Bajers Vej D3-203, 9220 Aalborg Ø, Denmark Email: Kristian Hennings* - [email protected]; Lars Arendt-Nielsen - [email protected]; Ole K Andersen - [email protected] * Corresponding author
Published: 12 April 2005 Theoretical Biology and Medical Modelling 2005, 2:16
doi:10.1186/1742-4682-2-16
Received: 08 December 2004 Accepted: 12 April 2005
This article is available from: http://www.tbiomed.com/content/2/1/16 © 2005 Hennings et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract Background: Accommodation and breakdown of accommodation are important elements of information processing in nerve fibers, as they determine how nerve fibers react to natural slowly changing stimuli or electrical stimulation. The aim of the present study was to elucidate the biophysical mechanism of breakdown of accommodation, which at present is unknown. Results: A model of a space-clamped motor nerve fiber was developed. It was found that this new model could reproduce breakdown of accommodation when it included a low-threshold, rapidly activating, persistent sodium current. However, the phenomenon was not reproduced when the persistent sodium current did not have fast activation kinetics or a low activation threshold. Conclusion: The present modeling study suggests that persistent, low-threshold, rapidly activating sodium currents have a key role in breakdown of accommodation, and that breakdown of accommodation can be used as a tool for studying persistent sodium current under normal and pathological conditions.
Background Accommodation is important for information processing in nerve fibers, as it determines whether, and how frequently, slowly-changing natural and artificial stimuli are translated into action potentials. Hill's theory of accommodation in nerve has been one of the most influential theories in this area [1]. A prediction of this theory is that a linearly rising current requires a certain critical slope in order to excite nerve fibers. Although this critical slope has been demonstrated in experimental preparations [2,3], it has not been found under normal physiological conditions [4,5]. Instead, nerve fibers have been shown to exhibit breakdown of accommodation; that is, a longduration slowly rising current excites nerve fibers at a nearly constant intensity no matter how slowly this intensity is approached [4,5]. A critical slope has only been
found for depolarized nerve fibers, and Hill's theory of accommodation has been shown only to be applicable to such fibers [6]. Accommodation and breakdown of acc
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