PMID- 28615333
OWN - NLM
STAT- MEDLINE
DCOM- 20180503
LR  - 20181202
IS  - 1522-1598 (Electronic)
IS  - 0022-3077 (Print)
IS  - 0022-3077 (Linking)
VI  - 118
IP  - 2
DP  - 2017 Aug 1
TI  - Excitability and firing behavior of single slow motor axons transmitting natural 
      repetitive firing of human motoneurons.
PG  - 1355-1360
LID - 10.1152/jn.00233.2017 [doi]
AB  - Excitability of motor axons is critically important for realizing their main 
      function, i.e., transmitting motoneuron firing to muscle fibers. The present 
      study was designed to explore excitability recovery and firing behavior in single 
      slow axons transmitting human motoneuron firing during voluntary muscle 
      contractions. The abductor digiti minimi, flexor carpi ulnaris, and tibialis 
      anterior were investigated during threshold stimulation of corresponding motor 
      nerves. Motor unit (MU) firing index in response to testing volleys evoking 
      M-responses was used as a physiological measure of axonal excitability and its 
      changes throughout a target interspike interval (ISI) were explored. It was shown 
      that axons displayed an early irresponsive period (within the first ~2-5 ms of a 
      target ISI) that was followed by a responsive period (for the next 5-17 ms of the 
      ISI), in which MUs fired axonal doublets, and a later irresponsive period. At the 
      beginning of the responsive period, M-responses showed small latency delays. 
      However, since at that ISI moment, MUs displayed excitability recovery with high 
      firing index, slight latency changes may be considered as a functionally 
      insignificant phenomenon. The duration of axonal doublet ISIs did not depend on 
      motoneuron firing frequencies (range 4.3-14.6 imp/s). The question of whether or 
      not traditionally described axonal recovery excitability cycle is realistic in 
      natural motor control is discussed. In conclusion, the present approach, 
      exploring, for the first time, excitability recovery in single slow axons during 
      motoneuron natural activation, can provide further insight into axonal firing 
      behavior in normal states and diseases.NEW & NOTEWORTHY Excitability of single 
      slow axons was estimated by motor unit firing index in response to motor nerve 
      stimulation, and its changes throughout a target interspike interval were 
      explored during transmitting human motoneuron natural firing. It was found that 
      axons exhibited early irresponsive, responsive, and later irresponsive periods. 
      Findings question whether the traditionally described axonal excitability 
      recovery cycle is realistic in natural motor control.
CI  - Copyright (c) 2017 the American Physiological Society.
FAU - Kudina, Lydia P
AU  - Kudina LP
AD  - Institute for Information Transmission Problems, Kharkevich Institute, Russian 
      Academy of Sciences, Moscow, Russia kudina@iitp.ru.
FAU - Andreeva, Regina E
AU  - Andreeva RE
AD  - Institute for Information Transmission Problems, Kharkevich Institute, Russian 
      Academy of Sciences, Moscow, Russia.
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
DEP - 20170614
PL  - United States
TA  - J Neurophysiol
JT  - Journal of neurophysiology
JID - 0375404
SB  - IM
MH  - Adult
MH  - Axons/*physiology
MH  - *Evoked Potentials, Motor
MH  - Humans
MH  - Middle Aged
MH  - Motor Neurons/*physiology
MH  - Muscle Contraction
MH  - Reaction Time
PMC - PMC5558025
OTO - NOTNLM
OT  - axonal excitability
OT  - axonal firing behavior
OT  - human motoneuron natural firing
OT  - motor control
OT  - single slow motor axons
EDAT- 2017/06/16 06:00
MHDA- 2018/05/04 06:00
PMCR- 2018/08/01
CRDT- 2017/06/16 06:00
PHST- 2017/03/29 00:00 [received]
PHST- 2017/06/14 00:00 [revised]
PHST- 2017/06/14 00:00 [accepted]
PHST- 2017/06/16 06:00 [pubmed]
PHST- 2018/05/04 06:00 [medline]
PHST- 2017/06/16 06:00 [entrez]
PHST- 2018/08/01 00:00 [pmc-release]
AID - jn.00233.2017 [pii]
AID - JN-00233-2017 [pii]
AID - 10.1152/jn.00233.2017 [doi]
PST - ppublish
SO  - J Neurophysiol. 2017 Aug 1;118(2):1355-1360. doi: 10.1152/jn.00233.2017. Epub 
      2017 Jun 14.