Abstract
Action-potential-encoded optical second harmonic generation (SHG) has been recently proposed for use in detecting the axonal damage in patients with demyelinating diseases. In this study, the characterization of signal conduction along axons of two different levels of demyelination was studied via a modified Hodgkin–Huxley model, because some types of demyelinating disease, i.e., primary progressive and secondary progressive multiple sclerosis, are difficult to be distinguished by magnetic resonance imaging (MRI), we focused on the differences in signal conduction between two different demyelinated axons, such as the first-level demyelination and the second-level demyelination. The spatio-temporal distribution of action potentials along demyelinated axons and conduction properties including the refractory period and frequency encoding in these two patterns were investigated. The results showed that demyelination could induce the decrease both in the amplitude of action potentials and the ability of frequency coding. Furthermore, the signal conduction velocity in the second-level demyelination was about 21% slower than that in the first-level demyelination. The refractory period in the second-level demyelination was about 32% longer than the first-level. Thus, detecting the signal conduction in demyelinated axons by action-potential-encoded optical SHG could greatly improve the assessment of demyelinating disorders to classify the patients. This technique also offers a potential fast and noninvasive optical approach for monitoring membrane potential.
Highlights
The characterization of signal conduction along axons of two di®erent levels of demyelination was studied via a modied Hodgkin–Huxley model, because some types of demyelinating disease, i.e., primary progressive and secondary progressive multiple sclerosis, are di±cult to be distinguished by magnetic resonance imaging (MRI), we focused on the di®erences in signal conduction between two di®erent demyelinated axons, such as therst-level demyelination and the secondlevel demyelination
Dombeck et al found that second harmonic generation (SHG) technique is better to record the action potential than TPEF with the lipophilic styryl dye FM4-64.4,5 Nuriya et al carried out SHG imaging of membrane potentials in axons and dendritic spines in cultured hippocampal neurons to study the basic principles of voltage propagation.[6,7]
Signal conduction properties in therst-level demyelinated axon and the second-level demyelinated axon were investigated by action-potentialencoded optical SHG
Summary
Action-potential-encoded optical second harmonic generation (SHG) has been recently proposed for use in detecting the axonal damage in patients with demyelinating diseases. Detecting the signal conduction in demyelinated axons by action-potential-encoded optical SHG could greatly improve the assessment of demyelinating disorders to classify the patients. This technique o®ers a potential fast and noninvasive optical approach for monitoring membrane potential. We focused on the di®erences in signal conduction between these two models These two demyelinated axons could be distinguished by studying the spatiotemporal distribution of action potentials and conduction properties including the refractory period and the frequency coding.
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