Abstract
Objectives. To investigate the properties of the strength-duration time constant (SDTC) in multiple sclerosis (MS) patients. Methods. The SDTC and rheobase in 16 MS patients and 19 healthy controls were obtained following stimulation of the right median nerve at the wrist. Results. SDTC and rheobase values were 408.3 ± 60.0 μs and 4.0 ± 1.8 mA in MS patients, versus 408.0 ± 62.4 μs and 3.8 ± 2.1 mA in controls. The differences were not significant in SDTC or rheobase values between the patients and controls (P = 0.988 for SDTC and P = 0.722 for rheobase). Conclusion. Our study showed no abnormality in relapsing remitting MS patients in terms of SDTC, which gives some indirect information about peripheral Na+ channel function. This may indicate that alterations in the Na+ channel pattern in central nervous system (CNS) couldnot be shown in the peripheral nervous system (PNS) in the MS patients by SDTC. The opinion that MS can be a kind of channelopathy might be proven by performing other axonal excitability tests or SDTC in progressive forms of MS.
Highlights
Ion channels play an essential role in signal transmission and production of the action potentials by controlling anion and cation membrane traffic
It might not be correct to consider that Na+ channels in peripheral nerves of multiple sclerosis (MS) are completely unaffected according to our study
The absence of significant difference in peripheral intranodal Na+ channel functioning between the MS patients and controls in the present study indicates that alterations in the Na+ channel pattern, which have been shown in the central nervous system (CNS) of MS patients, could not be shown in peripheral nervous system (PNS) of MS patients by strength-duration time constant (SDTC)
Summary
Ion channels play an essential role in signal transmission and production of the action potentials by controlling anion and cation membrane traffic. These channels are important for normal functioning of the excitable tissues of the nervous system. Molecular genetics had shown that diseases due to gene encoding mutations in the ion channel subunits of cell membranes are channelopathies [1]. Ion channel mutations may affect whole nervous system. Channelopathies are often inherited, those associated with autoimmune mechanisms have been recently described [1]. Apart from this, channelopathies resulting from the aberrant transcription of a normal gene are named transcriptional channelopathies. Peripheral nerve injury and multiple sclerosis can lead to altered transcription [3]
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