Neuroscience 2000 Abstract
| Presentation Number: | 257.9 |
|---|---|
| Abstract Title: | The role of the axon in dynamic firing properties of motoneuron models. |
| Authors: |
McIntyre, C. C.*1
; Grill, W. M.1
1Dept Biomed Engineering, Case Western Reserve Univ, Cleveland, OH |
| Primary Theme and Topics |
G. Motor Systems and Sensorimotor Integration - 92. Spinal cord and brainstem |
| Secondary Theme and Topics | C. Excitable Membranes and Synaptic Transmission<br />- 35. Sodium channels |
| Session: |
257. Spinal cord and brainstem: motor neuron properties Poster |
| Presentation Time: | Monday, November 6, 2000 8:00 AM-9:00 AM |
| Location: | Hall G-J |
| Keywords: | SODIUM CHANNEL, POTASSIUM CHANNEL, CALCIUM CHANNEL |
Previous attempts to model motoneuron action potentials, spike frequency adaptation, and steady-state repetitive discharge behavior have relied on geometrically simple models that do not explicitly represent the myelinated axon of the neuron. However, there is evidence that action potential initiation (API), from current injection into the cell body or excitatory synaptic input, takes place not in the cell body or initial segment, but in a node of the myelinated axon. The goal of this study was to develop motoneuron models that represent the complete neuronal architecture, and the ion channel type and density in the different neural elements. The models consisted of a myelinated axon, initial segment, soma, and either a three-dimensional branching dendritic tree or a single equivalent tapering cylinder. The nodes of the axon had fast sodium (INa), persistant sodium (INap), slow potassium, and leakage (IL) channels. The initial segment had INa, INap, delayed rectifier potassium (IKdr), and IL channels. The soma had INa, IKdr, calcium-activated potassium, L-type calcium, N-type calcium, and IL channels. The dendrites had IL channels. The membrane dynamics describing these different channels were derived from previous physiological and theoretical studies, and the models were able to reproduce a wide range of experimental results including input resistance (RN), time constant (τ) and after-hyperpolarization (AHP) shape. The presence of the axon influenced the electrical properties of the model and resulted in a decrease in RN, a decrease in τ, and a decrease in the AHP magnitude and time course. The presence of the axon also resulted in a decrease in the rate of spike frequency adaptation and a decrease in the steady-state repetitive discharge frequency. The results of this study suggest the axon is not only an important element in API but also plays a significant role in the dynamic firing properties of the motoneuron. This work was supported by a grant (BES-9709488) from the NSF and a training fellowship (HD-07500) from the NIH.
Supported by a grant (BES-9709488) from the NSF and a training fellowship (HD-07500) from the NIH.
Sample Citation:
[Authors]. [Abstract Title]. Program No. XXX.XX. 2000 Neuroscience Meeting Planner. New Orleans, LA: Society for Neuroscience, 2000. Online.
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