Interneurons transiently express the ERG K+ channels during development of mouse spinal networks in vitro

ERG Conductance Expression Modulates the Excitability of Ventral Horn GABAergic Interneurons That Control Rhythmic Oscillations in the Developing Mouse Spinal Cord

“…The pH was adjusted to 7.4 with NaOH (osmolarity, 305 mOsm).Current-clamp recordings in the whole-cell configuration (patch-clamp) were obtained at room temperature (RT) (22 Ϯ 2°C) from visually identified ventral spinal neurons with pipettes (4 -6 M⍀) filled with a solution of the following composition (in mM): 120 K-gluconate, 20 KCl, 10 HEPES, 10 EGTA, 2 MgCl 2 , and 2 Na 2 ATP; pH 7.35 with KOH. In accordance with previous investigations (Streit et al, 1991;Ballerini and Galante, 1998;Ballerini et al, 1999;Galante et al, 2000;Rosato-Siri et al, 2002;Avossa et al, 2003;Furlan et al, 2005), neurons were empirically termed interneurons when their cell body diameter was between 10 and 20 m, thus making them clearly distinguishable from cells morphologically resembling motoneurons (30 -60 m diameter) and immunoreactive to the motoneuron marker SMI32 (supplemental Fig. 2, available at www.jneurosci.org as supplemental material).Unlike interneurons, motoneurons generated long processes that often terminated on the muscle fibers distributed laterally to the slice (Ballerini et al, 1999;Avossa et al, 2003).…”

“…Organotypic slice cultures of spinal cord and dorsal root ganglia (DRG) were obtained from mouse embryos (F1 hybrid C57BL6ϫSJL) at days 12-13 of gestation, as described previously (Avossa et al, 2003;Furlan et al, 2005). Briefly, the fetuses were obtained by cesarean delivery from timedpregnant anesthetized mice (chloral hydrate 10.5%, 0.4 ml/100 g, i.m.)…”

“…Several maturation processes take place in spinal slices grown for 1 or 2 weeks in vitro (Avossa et al, 2003;Rosato-Siri et al, 2004;Furlan et al, 2005). Our previous studies have indicated important differences in network activity between 1 week and 2 weeks of organotypic culturing (Ballerini and Galante, 1998;Rosato-Siri et al, 2004); therefore, these were taken as crucial time points to investigate the potential role of ERG in shaping circuit discharges.…”

“…Given the importance of GABA-dependent depolarizations as developmental signals (Ben-Ari, 2002;Owens and Kriegstein, 2002;Alvarez et al, 2005), it is necessary to clarify the processes regulating the embryonic GABAergic phenotype. Using organotypic slice cultures as an in vitro model system of spinal network development, we have recently reported that all embryonic GABAergic interneurons express m-erg genes and ERG proteins (Furlan et al, 2005). The erg genes code for a potassium current termed I K(ERG) (Schwarz and Bauer, 2004) that possesses unusual kinetic characteristics, including fast inactivation with strong resurgent properties after hyperpolarization (Chiesa et al, 1997;Sacco et al, 2003).…”

IFIH1-GCA-KCNH7 locus: influence on multiple sclerosis risk

“…4 Among voltage-dependent K þ channels, the ERG subfamily is mainly involved in the control of cellular excitability, both in mammals and in invertebrates. 5,6 Moreover, macrophages and neutrophils are key cellular components of innate immunity and the GCA grancalcin gene, located between IFIH1 and KCNH7 genes, is highly expressed in both types of leukocytes. 7 More recently, association of this locus with Grave's disease was also found.…”