Skip to main content
Journal cover image

Adaptation of cat motoneurons to sustained and intermittent extracellular activation.

Publication ,  Journal Article
Spielmann, JM; Laouris, Y; Nordstrom, MA; Robinson, GA; Reinking, RM; Stuart, DG
Published in: J Physiol
May 1993

1. The main purpose of this study was to quantify the adaptation of spinal motoneurons to sustained and intermittent activation, using an extracellular route of stimulating current application to single test cells, in contrast to an intracellular route, as has been used previously. In addition, associations were tested between firing rate properties of the tested cells and other type (size)-related properties of these cells and their motor units. 2. Motoneurons supplying the medial gastrocnemius muscle of the deeply anaesthetized cat were stimulated for 240 s with microelectrodes which passed sustained extracellular current at 1.25 times the threshold for repetitive firing. Many cells were also tested following a rest period with intermittent 1 s current pulses (duration 600 ms) at the same relative stimulus strength. Cell discharge was assessed from the EMG of the motor unit innervated by the test neuron. The motoneurons and their motor units were assigned to four categories (i.e. types FF, FR, S and F; where F = FF + FR) based on conventional criteria. In all, twenty F (16 FF, 4 FR) and fourteen S cells were studied with sustained stimulation. Thirty of these cells (17 F, 13 S) and an additional two cells (1 F, 1 S) were studied with intermittent stimulation. 3. The mean threshold current required for sustained firing for a period of > or = 2 s was not significantly different for F and S cells. However, most of the other measured parameters of motoneuron firing differed significantly for these two cell groups. For example, at 1.25 times the threshold current for repetitive firing, the mean firing duration in response to 240 s of sustained activation was 123 +/- 88 s (+/- S.D.) for F cells vs. 233 +/- 19 s for S cells. These values were significantly longer than those from a comparable, previously reported study that employed intracellular stimulation. With intermittent stimulation, the firing durations of F and S cells were not significantly different from each other. 4. All cells exhibited a delay from the onset of current to the first spike, followed by a brief accelerating discharge that was followed by a slower drop in firing rate. Some cells (21 of 34 with sustained activation; 20 of 32 with intermittent) exhibited doublet discharges (interspike intervals < or = 10 ms) that were intermingled with the more predominant singlet discharges. Doublets were more common in the S cell type.(ABSTRACT TRUNCATED AT 400 WORDS)

Duke Scholars

Published In

J Physiol

DOI

ISSN

0022-3751

Publication Date

May 1993

Volume

464

Start / End Page

75 / 120

Location

England

Related Subject Headings

  • Reaction Time
  • Physiology
  • Motor Neurons
  • Intracellular Membranes
  • Extracellular Space
  • Electrophysiology
  • Electric Stimulation
  • Differential Threshold
  • Cats
  • Animals
 

Citation

APA
Chicago
ICMJE
MLA
NLM
Spielmann, J. M., Laouris, Y., Nordstrom, M. A., Robinson, G. A., Reinking, R. M., & Stuart, D. G. (1993). Adaptation of cat motoneurons to sustained and intermittent extracellular activation. J Physiol, 464, 75–120. https://doi.org/10.1113/jphysiol.1993.sp019625
Spielmann, J. M., Y. Laouris, M. A. Nordstrom, G. A. Robinson, R. M. Reinking, and D. G. Stuart. “Adaptation of cat motoneurons to sustained and intermittent extracellular activation.J Physiol 464 (May 1993): 75–120. https://doi.org/10.1113/jphysiol.1993.sp019625.
Spielmann JM, Laouris Y, Nordstrom MA, Robinson GA, Reinking RM, Stuart DG. Adaptation of cat motoneurons to sustained and intermittent extracellular activation. J Physiol. 1993 May;464:75–120.
Spielmann, J. M., et al. “Adaptation of cat motoneurons to sustained and intermittent extracellular activation.J Physiol, vol. 464, May 1993, pp. 75–120. Pubmed, doi:10.1113/jphysiol.1993.sp019625.
Spielmann JM, Laouris Y, Nordstrom MA, Robinson GA, Reinking RM, Stuart DG. Adaptation of cat motoneurons to sustained and intermittent extracellular activation. J Physiol. 1993 May;464:75–120.
Journal cover image

Published In

J Physiol

DOI

ISSN

0022-3751

Publication Date

May 1993

Volume

464

Start / End Page

75 / 120

Location

England

Related Subject Headings

  • Reaction Time
  • Physiology
  • Motor Neurons
  • Intracellular Membranes
  • Extracellular Space
  • Electrophysiology
  • Electric Stimulation
  • Differential Threshold
  • Cats
  • Animals