title: Hyperpolarization-activated cation current contributes to spontaneous network activity in developing neocortical cultures.
abstract: The mechanisms underlying spontaneous burst activity (SBA), appearing in networks of embryonic cortical neurons at the end of the first week in vitro, remain elusive. Here we investigated the contribution of the hyperpolarization-activated cation current (I(h)) to SBA in cortical cultures of GAD67-GFP mice. I(h) current could be detected in GFP-positive large GABAergic interneurons (L-INs) and glutamatergic principal neurons (PNs) as early as DIV 5. Under current-clamp conditions, blockers of I(h) current, ZD7288 and Cs⁺, abolished the voltage sag and rebound depolarization. ZD7288 induced a hyperpolarization concomitant with an increase in the membrane input resistance in L-INs and PNs. Voltage-clamp recordings revealed I(h) as slowly activating inward current with a reversal potential close to -50 mV and a mid-activation point around -90 mV. Both, ZD7288 (1-10 μM) and Cs⁺ (1-2 mM) reduced SBA, spontaneous activity-driven Ca²⁺ transients, and frequency as well as amplitude of miniature GABAergic postsynaptic currents. Immunocytochemistry and Western blot demonstrated that HCN1 and HCN2 were the prevalent isoforms of HCN channels expressed in L-INs and PNs. These results suggest an important contribution of HCN channels to the maintenance of SBA in embryonic cortical cultures.
authors.affiliation: Institut für Physiologie, Medizinische Fakultät, Otto-von-Guericke-Universität, Magdeburg, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Klueva
authors.forename: Ana D de
authors.initials: AD
authors.lastname: Lima
authors.forename: Susanne
authors.initials: S
authors.lastname: Meis
authors.forename: Thomas
authors.initials: T
authors.lastname: Voigt
authors.forename: Thomas
authors.initials: T
authors.lastname: Munsch
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D054815:Cyclic Nucleotide-Gated Cation Channels / Q000502:physiology*; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D007473:Ion Channels / Q000502:physiology*; D008564:Membrane Potentials / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D019579:Neocortex / Q000166:cytology / Q000196:embryology* / Q000254:growth & development*; D009415:Nerve Net / Q000166:cytology / Q000196:embryology* / Q000254:growth & development*; D009431:Neural Conduction / Q000502:physiology; D015221:Potassium Channels / Q000502:physiology*; D020033:Protein Isoforms / Q000502:physiology
chemical_list: D054815:Cyclic Nucleotide-Gated Cation Channels; C578666:Hcn1 protein, mouse; C578711:Hcn2 protein, mouse; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D007473:Ion Channels; D015221:Potassium Channels; D020033:Protein Isoforms