Persistent inward currents in rat ventral horn neurones.
Throughout the mammalian spinal cord, interneurones have been shown to exhibit distinct firing patterns in response to a step of injected current. In this study of ventral horn interneurones in a thick slice preparation of the lumbar cord of 11-19-day-old-rats, four distinct firing patterns were observed and classified as repetitive-firing, repetitive/burst, initial-burst or single-spiking. The hypothesis that a persistent sodium current was the predominant determinant of cell firing behaviour was investigated. A slow voltage ramp was used to assess persistent inward currents (PICs). Cells with repetitive-firing patterns had significantly larger PICs than cells displaying repetitive/burst, initial-burst or single-spiking patterns. Repetitive-firing, repetitive/burst and initial-burst-firing cells were reduced to a single-spiking pattern with the application of riluzole, which also markedly reduced the persistent sodium current. Persistent sodium current was found to account for most of the PIC with only a small contribution from L-type calcium current. These results suggest that the persistent sodium current plays a major role in determining firing patterns in these cells.
Theiss
Renée D
RD
Department of Physiology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA.
Kuo
Jason J
JJ
Heckman
C J
CJ
D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D000870:Anterior Horn Cells / Q000502:physiology*; D002118:Calcium / Q000378:metabolism; D020746:Calcium Channels, L-Type / Q000502:physiology; D004594:Electrophysiology; D066298:In Vitro Techniques; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D012964:Sodium / Q000378:metabolism* / Q000502:physiology
D020746:Calcium Channels, L-Type; D012964:Sodium; D002118:Calcium