title: Postnatal development of A-type and Kv1- and Kv2-mediated potassium channel currents in neocortical pyramidal neurons.
abstract: Potassium channels regulate numerous aspects of neuronal excitability, and several voltage-gated K(+) channel subunits have been identified in pyramidal neurons of rat neocortex. Previous studies have either considered the development of outward current as a whole or divided currents into transient, A-type and persistent, delayed rectifier components but did not differentiate between current components defined by α-subunit type. To facilitate comparisons of studies reporting K(+) currents from animals of different ages and to understand the functional roles of specific current components, we characterized the postnatal development of identified Kv channel-mediated currents in pyramidal neurons from layers II/III from rat somatosensory cortex. Both the persistent/slowly inactivating and transient components of the total K(+) current increased in density with postnatal age. We used specific pharmacological agents to test the relative contributions of putative Kv1- and Kv2-mediated currents (100 nM α-dendrotoxin and 600 nM stromatoxin, respectively). A combination of voltage protocol, pharmacology, and curve fitting was used to isolate the rapidly inactivating A-type current. We found that the density of all identified current components increased with postnatal age, approaching a plateau at 3-5 wk. We found no significant changes in the relative proportions or kinetics of any component between postnatal weeks 1 and 5, except that the activation time constant for A-type current was longer at 1 wk. The putative Kv2-mediated component was the largest at all ages. Immunocytochemistry indicated that protein expression for Kv4.2, Kv4.3, Kv1.4, and Kv2.1 increased between 1 wk and 4-5 wk of age.
authors: Department of Anatomy and Neurobiology, University of Tennessee Health Science Center, Memphis, TN 38163, USA.
authors: Dongxu
authors: D
authors: Guan
authors: Leslie R
authors: LR
authors: Horton
authors: William E
authors: WE
authors: Armstrong
authors: Robert C
authors: RC
authors: Foehring
mesh_terms: D000367:Age Factors; D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D001703:Biophysics; D002478:Cells, Cultured; D051668:Delayed Rectifier Potassium Channels / Q000378:metabolism; D004347:Drug Interactions; D004558:Electric Stimulation / Q000379:methods; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D019579:Neocortex / Q000166:cytology* / Q000254:growth & development*; D018408:Patch-Clamp Techniques / Q000379:methods; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000378:metabolism*; D017966:Pyramidal Cells / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D051669:Shab Potassium Channels / Q000378:metabolism; D051637:Shaker Superfamily of Potassium Channels / Q000378:metabolism
chemical_list: D051668:Delayed Rectifier Potassium Channels; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D051669:Shab Potassium Channels; D051637:Shaker Superfamily of Potassium Channels