Identified Ankle Extensor and Flexor Motoneurons Display Different Firing Profiles in the Neonatal Rat - Archive ouverte HAL
Autre Publication Scientifique Journal of Neuroscience Année : 2009

Identified Ankle Extensor and Flexor Motoneurons Display Different Firing Profiles in the Neonatal Rat

Florence Cotel
  • Fonction : Auteur
Myriam Antri
Jean-Yves Barthe
  • Fonction : Auteur

Résumé

The present study was designed to compare the firing profiles exhibited by lumbar flexor or extensor motoneurons in response to injection of depolarizing/repolarizing currents. Motoneurons were recorded intracellularly in the in vitro brainstem-spinal cord of newborn rats (P4–P7). They were synaptically isolated and identified by antidromic stimulations of the central stump of flexor or extensor muscle nerves: tibialis anterior (ankle flexor) and gastrocnemius medialis or lateralis (ankle extensors). Two protocols were applied to establish the four firing profiles previously described (type I–IV) (Bennett et al., 2001): (1) symmetric depolarizing/repolarizing ramps of current and (2) progressive steps of depolarizing currents followed by equivalent steps of repolarizing current. According to such profiles, this study clearly shows that flexor and extensor motoneurons are different. The whole population of flexor motoneurons solely exhibited the type II profile, characterized by a frequency–current ( F–I ) relationship with a clockwise hysteresis. In contrast, in addition to this type II profile, the other three profiles of repetitive firing (type I, III and IV) were observed in extensor motoneurons; a linear F–I relationship (type I profile), a self-sustained discharge pattern together with a linear F–I relationship (type III profile) and a self-sustained firing pattern together with an F–I relationship showing a counter-clockwise hysteresis (type IV profile). Thus, during the early postnatal development, a significant part of the population of extensor motoneurons, but not flexors, are able to produce self-sustained discharges known to involve the activation of persistent inward currents.

Dates et versions

hal-04326262 , version 1 (06-12-2023)

Identifiants

Citer

Florence Cotel, Myriam Antri, Jean-Yves Barthe, Didier Orsal. Identified Ankle Extensor and Flexor Motoneurons Display Different Firing Profiles in the Neonatal Rat. 2009, pp.2748-2753. ⟨10.1523/JNEUROSCI.3462-08.2009⟩. ⟨hal-04326262⟩
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