The persistent sodium current generates pacemaker activities in the central pattern generator for locomotion and regulates the locomotor rhythm.
Rhythm generation in neuronal networks relies on synaptic interactions and pacemaker properties. Little is known about the contribution of the latter mechanisms to the integrated network activity underlying locomotion in mammals. We tested the hypothesis that the persistent sodium current (I(NaP)) is critical in generating locomotion in neonatal rodents using both slice and isolated spinal cord preparations. After removing extracellular calcium, 75% of interneurons in the area of the central pattern generator (CPG) for locomotion exhibited bursting properties and I(NaP) was concomitantly upregulated. Putative CPG interneurons such as commissural and Hb9 interneurons also expressed I(NaP)-dependent (riluzole-sensitive) bursting properties. Most bursting cells exhibited a pacemaker-like behavior (i.e., burst frequency increased with depolarizing currents). Veratridine upregulated I(NaP), induced riluzole-sensitive bursting properties, and slowed down the locomotor rhythm. This study provides evidence that I(NaP) generates pacemaker activities in CPG interneurons and contributes to the regulation of the locomotor activity.
Tazerart
Sabrina
S
Laboratoire Plasticité et Physio-Pathologie de la Motricité, Unité Mixte de Recherche 6196, Centre National de la Recherche Scientifique, Université Aix-Marseille, F-13402 Marseille Cedex 20, France.
Vinay
Laurent
L
Brocard
Frédéric
F
D000818:Animals; D000831:Animals, Newborn; D001683:Biological Clocks / Q000187:drug effects / Q000502:physiology*; D002118:Calcium / Q000378:metabolism; D004594:Electrophysiology; D005110:Extracellular Space / Q000378:metabolism; D005456:Fluorescent Dyes; D049452:Green Fluorescent Proteins / Q000235:genetics; D018398:Homeodomain Proteins / Q000235:genetics; D066298:In Vitro Techniques; D007395:Interneurons / Q000502:physiology; D008124:Locomotion / Q000502:physiology*; D051379:Mice; D008822:Mice, Transgenic; D010507:Periodicity; D051381:Rats; D017208:Rats, Wistar; D015222:Sodium Channels / Q000187:drug effects / Q000502:physiology*; D013116:Spinal Cord / Q000166:cytology / Q000502:physiology*; D014701:Veratridine / Q000494:pharmacology
D005456:Fluorescent Dyes; D018398:Homeodomain Proteins; D015222:Sodium Channels; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D014701:Veratridine; D002118:Calcium