Estimation of the Contribution of Intrinsic Currents to Motoneuron Firing Based on Paired Motoneuron Discharge Records in the Decerebrate Cat

Randall K. Powers, Paul Nardelli, T. C. Cope

Research output: Contribution to journalArticlepeer-review

Abstract

Motoneuron activation is strongly influenced by persistent inward currents (PICs) flowing through voltage-sensitive channels. PIC characteristics and their contribution to the control of motoneuron firing rate have been extensively described in reduced animal preparations, but their contribution to rate modulation in human motoneurons is controversial. It has recently been proposed that the analysis of discharge records of a simultaneously recorded pair of motor units can be used to make quantitative estimates of the PIC contribution, based on the assumption that the firing rate of an early recruited (reporter) unit can be used as a measure of the synaptic drive to a later recruited (test) unit. If the test unit's discharge is augmented by PICs, less synaptic drive will be required to sustain discharge than required to initially recruit it, and the difference in reporter unit discharge (Δ F ) at test recruitment and de-recruitment is a measure of the size of the PIC contribution. We applied this analysis to discharge records of pairs of motoneurons in the decerebrate cat preparation, in which motoneuron PICs have been well-characterized and are known to be prominent. Mean Δ F values were positive in 58/63 pairs, and were significantly greater than zero in 40/63 pairs, as would be expected based on PIC characteristics recorded in this preparation. However, several lines of evidence suggest that the Δ F value obtained in a particular motoneuron pair may depend on a number of factors other than the PIC contribution to firing rate.

Original languageEnglish
Pages (from-to)292-303
Number of pages12
JournalJournal of Neurophysiology
Volume100
Issue number1
DOIs
StatePublished - Jul 2008
Externally publishedYes

ASJC Scopus Subject Areas

  • General Neuroscience
  • Physiology

Keywords

  • contribution
  • decerebrate cat
  • estimation
  • intrinsic currents
  • motoneuron firing
  • paired motoneuron discharge records

Disciplines

  • Medical Cell Biology
  • Medical Neurobiology
  • Medical Physiology
  • Neurosciences
  • Physiological Processes

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