title: Activity-dependent changes in extracellular Ca2+ and K+ reveal pacemakers in the spinal locomotor-related network.
abstract: Changes in the extracellular ionic concentrations occur as a natural consequence of firing activity in large populations of neurons. The extent to which these changes alter the properties of individual neurons and the operation of neuronal networks remains unknown. Here, we show that the locomotor-like activity in the isolated neonatal rodent spinal cord reduces the extracellular calcium ([Ca(2+)]o) to 0.9 mM and increases the extracellular potassium ([K(+)]o) to 6 mM. Such changes in [Ca(2+)]o and [K(+)]o trigger pacemaker activities in interneurons considered to be part of the locomotor network. Experimental data and a modeling study show that the emergence of pacemaker properties critically involves a [Ca(2+)]o-dependent activation of the persistent sodium current (INaP). These results support a concept for locomotor rhythm generation in which INaP-dependent pacemaker properties in spinal interneurons are switched on and tuned by activity-dependent changes in [Ca(2+)]o and [K(+)]o.
authors.affiliation: Team P3M, Institut de Neurosciences de la Timone, UMR 7289, CNRS and Aix-Marseille Université, F-13385 Marseille, France. frederic.brocard@univ-amu.fr
authors.forename: Frédéric
authors.initials: F
authors.lastname: Brocard
authors.forename: Natalia A
authors.initials: NA
authors.lastname: Shevtsova
authors.forename: Mouloud
authors.initials: M
authors.lastname: Bouhadfane
authors.forename: Sabrina
authors.initials: S
authors.lastname: Tazerart
authors.forename: Uwe
authors.initials: U
authors.lastname: Heinemann
authors.forename: Ilya A
authors.initials: IA
authors.lastname: Rybak
authors.forename: Laurent
authors.initials: L
authors.lastname: Vinay
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001683:Biological Clocks / Q000502:physiology*; D002118:Calcium / Q000378:metabolism*; D045604:Extracellular Fluid / Q000378:metabolism* / Q000502:physiology; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D009043:Motor Activity / Q000502:physiology*; D009415:Nerve Net / Q000378:metabolism / Q000502:physiology; D009924:Organ Culture Techniques; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013116:Spinal Cord / Q000378:metabolism* / Q000502:physiology
chemical_list: D011188:Potassium; D002118:Calcium