title: Regulation of Ca2+-dependent K+ channel expression in rat cerebellum during postnatal development.
abstract: Potassium channels govern duration and frequency of excitable membrane events and may regulate signals that are important in neuronal development. This study assesses the developmental expression of the large conductance Ca2+-dependent K+ channel in vivo and in vitro in rat cerebellum. In vivo, transcript levels for the Ca2+-dependent K+ channel (KCa) were shown by Northern analysis to increase during development, whereas transcript levels for the voltage-gated K+ channel Kv3.1, a delayed rectifier (KD), remained relatively constant. A comparable pattern was demonstrated by expression in Xenopus oocytes of poly(A)-enriched RNA isolated from postnatal rat cerebella. In cerebellar cultures, increased external K+ provided a simple manipulation of cell excitability that influenced KCa transcript levels during development. With low external K+ (5.3 mM), the levels of KCa channel transcript (assessed by semiquantitative PCR) remained constant throughout development. However, in culture medium that supported significant dendritic outgrowth (10 mM extracellular K+), an upregulation of KCa transcript level was observed similar to that seen in vivo. Tetraethylammonium (TEA; 1 mM) similarly enhanced KCa expression, suggesting that depolarizing stimuli increased KCa expression. The stimulatory effects of increased K+ or TEA on KCa expression required extracellular Ca2+ and were abolished in low external calcium (0.1 mM, buffered with EGTA), although morphological development and survival were not impaired. The regulation of KCa channel expression by depolarization and Ca2+ entry provides evidence of a logical feedback mechanism governing Ca2+ signals that may be significant in cerebellar development.
authors.affiliation: Department of Physiology, University of Arizona College of Medicine, Tucson, Arizona 85724-5051, USA.
authors.forename: Y L
authors.initials: YL
authors.lastname: Muller
authors.forename: R
authors.initials: R
authors.lastname: Reitstetter
authors.forename: A J
authors.initials: AJ
authors.lastname: Yool
mesh_terms: D000818:Animals; D015152:Blotting, Northern; D064026:Calbindins; D002118:Calcium / Q000494:pharmacology / Q000502:physiology*; D002478:Cells, Cultured; D002531:Cerebellum / Q000737:chemistry / Q000166:cytology / Q000254:growth & development*; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000235:genetics; D009865:Oocytes / Q000502:physiology; D018408:Patch-Clamp Techniques; D019696:Peptidylprolyl Isomerase / Q000235:genetics; D016133:Polymerase Chain Reaction; D011188:Potassium / Q000494:pharmacology; D015221:Potassium Channels / Q000235:genetics*; D011689:Purkinje Cells / Q000737:chemistry / Q000187:drug effects / Q000502:physiology*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D064030:S100 Calcium Binding Protein G / Q000235:genetics; D015398:Signal Transduction / Q000502:physiology; D019789:Tetraethylammonium / Q000494:pharmacology; D014158:Transcription, Genetic / Q000502:physiology; D014981:Xenopus
chemical_list: D064026:Calbindins; D009419:Nerve Tissue Proteins; D015221:Potassium Channels; D012333:RNA, Messenger; D064030:S100 Calcium Binding Protein G; D019789:Tetraethylammonium; D019696:Peptidylprolyl Isomerase; D011188:Potassium; D002118:Calcium