Premium
Differences in excitability properties of FDI and ADM motor axons
Author(s) -
Bae Jong Seok,
Sawai Setsu,
Misawa Sonoko,
Kanai Kazuaki,
Isose Sagiri,
Kuwabara Satoshi
Publication year - 2009
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/mus.21107
Subject(s) - amyotrophic lateral sclerosis , stimulation , stimulus (psychology) , motor nerve , dorsum , ulnar nerve , anatomy , compound muscle action potential , neuroscience , medicine , electrophysiology , biology , elbow , psychology , disease , psychotherapist
The first dorsal interosseous (FDI) and abductor digiti minimi (ADM) muscles are innervated by the same ulnar nerve, but studies have shown that the former is much more severely affected in amyotrophic lateral sclerosis. In this study, threshold tracking was used to investigate whether membrane properties differ between FDI and ADM motor axons. In 12 normal subjects, compound muscle action potentials were recorded from FDI and ADM after ulnar nerve stimulation at the wrist. The strength–duration time constant was significantly longer in the FDI axons than in the ADM axons, and latent addition studies showed greater threshold changes at the conditioning–test stimulus of 0.2 ms in FDI than in ADM axons. These findings suggest that nodal persistent sodium conductances are more prominent in FDI axons than in ADM axons, and therefore excitability is physiologically higher in FDI axons. Even in the same nerve at the same sites, membrane properties of FDI and ADM motor axons differ significantly, and thus their axonal/neuronal responses to disease may also differ. Muscle Nerve 39: 350–354, 2009