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Axon-somatic back-propagation in detailed models of spinal alpha motoneurons.

Balbi P, Martinoia S, Massobrio P - Front Comput Neurosci (2015)

Bottom Line: An axon hillock, an axonal initial segment and a myelinated axon are added to each model.By sweeping the diameter of the axonal initial segment (AIS) and the axon hillock, as well as the maximal conductances of sodium channels at the AIS and at the soma, the developed models are able to show the relationships between different geometric and electrophysiological configurations and the voltage attenuation of the antidromically traveling wave.In particular, a greater than usually admitted sodium conductance at AIS is necessary and sufficient to overcome the dramatic voltage attenuation occurring during antidromic spike propagation both at the myelinated axon-AIS and at the AIS-soma transitions.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurorehabilitation, Scientific Institute of Pavia via Boezio, IRCCS, 'Salvatore Maugeri' Foundation Pavia, Italy.

ABSTRACT
Antidromic action potentials following distal stimulation of motor axons occasionally fail to invade the soma of alpha motoneurons in spinal cord, due to their passing through regions of high non-uniformity. Morphologically detailed conductance-based models of cat spinal alpha motoneurons have been developed, with the aim to reproduce and clarify some aspects of the electrophysiological behavior of the antidromic axon-somatic spike propagation. Fourteen 3D morphologically detailed somata and dendrites of cat spinal alpha motoneurons have been imported from an open-access web-based database of neuronal morphologies, NeuroMorpho.org, and instantiated in neurocomputational models. An axon hillock, an axonal initial segment and a myelinated axon are added to each model. By sweeping the diameter of the axonal initial segment (AIS) and the axon hillock, as well as the maximal conductances of sodium channels at the AIS and at the soma, the developed models are able to show the relationships between different geometric and electrophysiological configurations and the voltage attenuation of the antidromically traveling wave. In particular, a greater than usually admitted sodium conductance at AIS is necessary and sufficient to overcome the dramatic voltage attenuation occurring during antidromic spike propagation both at the myelinated axon-AIS and at the AIS-soma transitions.

No MeSH data available.


(A) Examples of stimulus intensity-duration curve, for measuring the rheobase, in four representative motoneurons of the pool. (B) Action potentials following a brief (0.5 ms) somatic depolarizing current recorded from soma of the motoneuron v_e_moto5. The inset shows the first 15 ms of the induced action potential.
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Figure 2: (A) Examples of stimulus intensity-duration curve, for measuring the rheobase, in four representative motoneurons of the pool. (B) Action potentials following a brief (0.5 ms) somatic depolarizing current recorded from soma of the motoneuron v_e_moto5. The inset shows the first 15 ms of the induced action potential.

Mentions: The electrophysiological features of the simulated models are summarized in Table 5. The rheobase (minimal intensity of an infinitely long stimulus able to evoke a spike) was evaluated with a stimulus duration up to 1 s. Figure 2A shows four examples of stimulus intensity-duration curve relative to four alpha motoneuron models of different size.


Axon-somatic back-propagation in detailed models of spinal alpha motoneurons.

Balbi P, Martinoia S, Massobrio P - Front Comput Neurosci (2015)

(A) Examples of stimulus intensity-duration curve, for measuring the rheobase, in four representative motoneurons of the pool. (B) Action potentials following a brief (0.5 ms) somatic depolarizing current recorded from soma of the motoneuron v_e_moto5. The inset shows the first 15 ms of the induced action potential.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4325909&req=5

Figure 2: (A) Examples of stimulus intensity-duration curve, for measuring the rheobase, in four representative motoneurons of the pool. (B) Action potentials following a brief (0.5 ms) somatic depolarizing current recorded from soma of the motoneuron v_e_moto5. The inset shows the first 15 ms of the induced action potential.
Mentions: The electrophysiological features of the simulated models are summarized in Table 5. The rheobase (minimal intensity of an infinitely long stimulus able to evoke a spike) was evaluated with a stimulus duration up to 1 s. Figure 2A shows four examples of stimulus intensity-duration curve relative to four alpha motoneuron models of different size.

Bottom Line: An axon hillock, an axonal initial segment and a myelinated axon are added to each model.By sweeping the diameter of the axonal initial segment (AIS) and the axon hillock, as well as the maximal conductances of sodium channels at the AIS and at the soma, the developed models are able to show the relationships between different geometric and electrophysiological configurations and the voltage attenuation of the antidromically traveling wave.In particular, a greater than usually admitted sodium conductance at AIS is necessary and sufficient to overcome the dramatic voltage attenuation occurring during antidromic spike propagation both at the myelinated axon-AIS and at the AIS-soma transitions.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurorehabilitation, Scientific Institute of Pavia via Boezio, IRCCS, 'Salvatore Maugeri' Foundation Pavia, Italy.

ABSTRACT
Antidromic action potentials following distal stimulation of motor axons occasionally fail to invade the soma of alpha motoneurons in spinal cord, due to their passing through regions of high non-uniformity. Morphologically detailed conductance-based models of cat spinal alpha motoneurons have been developed, with the aim to reproduce and clarify some aspects of the electrophysiological behavior of the antidromic axon-somatic spike propagation. Fourteen 3D morphologically detailed somata and dendrites of cat spinal alpha motoneurons have been imported from an open-access web-based database of neuronal morphologies, NeuroMorpho.org, and instantiated in neurocomputational models. An axon hillock, an axonal initial segment and a myelinated axon are added to each model. By sweeping the diameter of the axonal initial segment (AIS) and the axon hillock, as well as the maximal conductances of sodium channels at the AIS and at the soma, the developed models are able to show the relationships between different geometric and electrophysiological configurations and the voltage attenuation of the antidromically traveling wave. In particular, a greater than usually admitted sodium conductance at AIS is necessary and sufficient to overcome the dramatic voltage attenuation occurring during antidromic spike propagation both at the myelinated axon-AIS and at the AIS-soma transitions.

No MeSH data available.