Area-specific resonance of excitatory networks in neocortex: control by outward currents.
During disinhibition or low [Mg++](o) buffer, 7-14 Hz ( approximately 10 Hz) oscillations are generated by excitatory networks of interconnected pyramidal cells in motor (agranular) cortex but are absent in barrel (granular) cortex. Here we studied if the inability of barrel cortex to produce approximately 10 Hz oscillations during these conditions is because barrel cortex networks lack the necessary cellular mechanisms or, alternatively, because those mechanisms are inhibited by outward currents. The results show that blockers of slowly inactivating voltage-dependent K+ currents unmask approximately 10 Hz oscillations in barrel cortex, and this occurs in unison with the unmasking of intrinsic inward Ca++ currents that are kept suppressed by the outward currents. Moreover, the approximately 10 Hz oscillations unmasked in barrel cortex occur independently in upper and lower layers indicating that the approximately 10 Hz oscillation mechanisms are kept suppressed in multiple networks. The results reveal that the propensity of distinct excitatory networks of neocortex to generate epileptiform oscillatory activities is controlled by outward currents.
Castro-Alamancos
Manuel A
MA
Department of Neurobiology and Anatomy, Drexel University College of Medicine, 2900 Queen Lane, Philadelphia, PA 19129, U.S.A. mcastro@drexelmed.edu
Tawara-Hirata
Yoshie
Y
D015761:4-Aminopyridine / Q000494:pharmacology; D000818:Animals; D058787:GABA-A Receptor Antagonists; D058788:GABA-B Receptor Antagonists; D008275:Magnesium Deficiency / Q000503:physiopathology; D051379:Mice; D008959:Models, Neurological; D009044:Motor Cortex / Q000187:drug effects / Q000502:physiology / Q000503:physiopathology; D019579:Neocortex / Q000187:drug effects / Q000502:physiology / Q000503:physiopathology*; D009433:Neural Inhibition / Q000502:physiology*; D009434:Neural Pathways / Q000187:drug effects / Q000502:physiology; D009991:Oscillometry; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000502:physiology; D017966:Pyramidal Cells / Q000187:drug effects / Q000502:physiology / Q000503:physiopathology; D011963:Receptors, GABA-A / Q000502:physiology; D018080:Receptors, GABA-B / Q000502:physiology
D058787:GABA-A Receptor Antagonists; D058788:GABA-B Receptor Antagonists; D011963:Receptors, GABA-A; D018080:Receptors, GABA-B; D015761:4-Aminopyridine; D011188:Potassium