Properties of low-threshold motor axons in the human median nerve

Trevillion, Louise; Howells, James; Bostock, Hugh; Burke, David (2010). Properties of low-threshold motor axons in the human median nerve. Journal of physiology, 588(Pt 13), pp. 2503-15. Oxford: Wiley-Blackwell 10.1113/jphysiol.2010.190884

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This study investigated the excitability and accommodative properties of low-threshold human motor axons to test whether these motor axons have greater expression of the persistent Na(+) conductance, I(NaP). Computer-controlled threshold tracking was used to study 22 single motor units and the data were compared with compound motor potentials of various amplitudes recorded in the same experimental session. Detailed comparisons were made between the single units and compound potentials that were 40% or 5% of maximal amplitude, the former because this is the compound potential size used in most threshold tracking studies of axonal excitability, the latter because this is the compound potential most likely to be composed entirely of motor axons with low thresholds to electrical recruitment. Measurements were made of the strength-duration relationship, threshold electrotonus, current-voltage relationship, recovery cycle and latent addition. The findings did not support a difference in I(NaP). Instead they pointed to greater activity of the hyperpolarization-activated inwardly rectifying current (I(h)) as the basis for low threshold to electrical recruitment in human motor axons. Computer modelling confirmed this finding, with a doubling of the hyperpolarization-activated conductance proving the best single parameter adjustment to fit the experimental data. We suggest that the hyperpolarization-activated cyclic nucleotide-gated (HCN) channel(s) expressed on human motor axons may be active at rest and contribute to resting membrane potential.

Item Type:

Journal Article (Original Article)

Division/Institute:

04 Faculty of Medicine > Department of Head Organs and Neurology (DKNS) > Clinic of Neurology

UniBE Contributor:

Bostock, Hugh

ISSN:

0022-3751

Publisher:

Wiley-Blackwell

Language:

English

Submitter:

Factscience Import

Date Deposited:

04 Oct 2013 14:14

Last Modified:

13 Jan 2016 16:29

Publisher DOI:

10.1113/jphysiol.2010.190884

PubMed ID:

20478975

Web of Science ID:

000279406600021

URI:

https://boris.unibe.ch/id/eprint/3339 (FactScience: 206999)

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