Volume 16, Issue 4 (Winter 2015)                   2015, 16(4): 22-31 | Back to browse issues page

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Bagheri M, Mahnam A, Rajaei Z. Extracellular Excitability of the Axon Terminals: The Effects of their Morphological Characteristics. Advances in Cognitive Science. 2015; 16 (4) :22-31
URL: http://icssjournal.ir/article-1-259-en.html
1- MSc, Biomedical Engineering, University of Isfahan,Isfahan,Iran.
2- Assistant Professor of Biomedical Engineering, University of Isfahan,Isfahan,Iran.
3- Assistant Professor of Physiology, Isfahan University of Medical Sciences,Isfahan,Iran.
Abstract:   (264 Views)
Introduction: In electrical stimulation of the central nervous system, different neural elements are present around the electrode and affected by the stimulation. The activation of each type of these neural elements may result in different overall neural responses. Previous studies have suggested that the passing axons and the initial segments of the local cells are the most excitable neural elements in cathodic and anodic stimulation, respectively. However, there are experimental evidences suggesting that the local fibers are generally excited indirectly by activation of the axon terminals of the presynaptic cells.  The axon terminal has been usually neglected in the analysis of extracellular excitability.
Methods: In this study, a detailed computational model of the axon terminal was used to study the extracellular excitability of the axon terminal. To this end, the effect of different geometrical characteristics of the axon terminals including their arborizations, conical synaptic buttons, and the swellings in the branching points on their excitability were studied in comparison to a passing fiber, where the electrode was far from the terminal.
Results: Our findings showed that branching of the axon terminal increases the excitability of the axon terminal up to 28% and 78% for cathodic and anodic stimulation, respectively.  In addition, the terminal arborizations which form the synaptic buttons as well as the swellings at the branching points could increase the excitability up to 7.5% and 34% for anodic and cathodic stimulation, respectively.
Conclusion: The present results suggest that geometric properties of the axon terminals increase the excitability of this segment, turning it to an important target in electrical stimulation. The activation of axon terminals may lead to different responses due to their inhibitory or excitatory effects on the local neurons.
Full-Text [PDF 946 kb]   (45 Downloads)    
Type of Study: Research | Subject: Special
Received: 2014/02/15 | Accepted: 2014/08/17 | Published: 2014/12/23

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