title: Characterization of maintained voltage-dependent K(+)-channels induced in Xenopus oocytes by rat brain mRNA.
abstract: The voltage-dependent K+ currents encoded by rat brain mRNA were studied in Xenopus oocytes after the voltage-dependent Na+ currents and the Ca(2+)-activated Cl- currents were eliminated pharmacologically. This paper describes the maintained K+ currents (IK), defined primarily by resistance to inactivation for 1 s at a holding potential of -40 mV. IK activates at potentials more positive than -60 to -70 mV and consists of both low-threshold and high-threshold components. IK is partially blocked by both tetraethyl ammonium (TEA) and 4-aminopyridine (4-AP), which appear to be blocking the same component. Long depolarizing pulses result in incomplete inactivation of IK; the inactivating component is inhibited by TEA. Sucrose density gradient fractionation partially resolves the RNA encoding the several components of IK; most IK arises from size classes between 3.8 and 9.5 kb. The study gives further evidence for the existence of numerous distinct RNA populations that encode brain K+ channels different from previously reported cloned K+ channels that have been expressed in Xenopus oocytes.
authors.affiliation: Division of Chemistry, California Institute of Technology, Pasadena 91125.
authors.forename: J H
authors.initials: JH
authors.lastname: Hoger
authors.forename: B
authors.initials: B
authors.lastname: Rudy
authors.forename: H A
authors.initials: HA
authors.lastname: Lester
authors.forename: N
authors.initials: N
authors.lastname: Davidson
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D015761:4-Aminopyridine / Q000494:pharmacology; D000818:Animals; D001923:Brain Chemistry; D002121:Calcium Channel Blockers / Q000494:pharmacology; D004594:Electrophysiology; D015640:Ion Channel Gating / Q000187:drug effects; D008564:Membrane Potentials; D008845:Microinjections; D009865:Oocytes / Q000378:metabolism*; D015221:Potassium Channels / Q000187:drug effects / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics* / Q000302:isolation & purification; D051381:Rats; D013574:Synaptosomes / Q000378:metabolism; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology; D014982:Xenopus laevis
chemical_list: D002121:Calcium Channel Blockers; D015221:Potassium Channels; D012333:RNA, Messenger; D013757:Tetraethylammonium Compounds; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D013779:Tetrodotoxin; D019789:Tetraethylammonium; D015761:4-Aminopyridine; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid