Bicuculline free base blocks voltage-activated K+ currents in rat medial preoptic neurons.
2004 (English)In: Neuropharmacology, ISSN 0028-3908, Vol. 46, no 2, 285-95 p.Article in journal (Refereed) Published
The effects of the well-known GABA(A)-receptor blocker bicuculline on voltage-gated K(+) currents were studied in neurons from the medial preoptic nucleus (MPN) of rat. Whole-cell currents were recorded using the perforated-patch technique. Voltage steps from -54 to +6 mV resulted in tetraethylammonium-sensitive K(+) currents of delayed rectifier type. The total K(+) current (at 300 ms), including Ca(2+)-dependent and Ca(2+)-independent components, was reversibly reduced (17 +/- 4%) by 100 microM bicuculline methiodide and (37 +/- 5%) by 100 microM bicuculline as free base. The Ca(2+)-independent fraction (77 +/- 2%) of K(+) current evoked by a voltage step was, however, reduced (54 +/- 6%) only by bicuculline free base, but was not affected by bicuculline methiodide. The half-saturating concentration of bicuculline free base for blocking this purely voltage-gated K(+) current was 113 microM, whereas for blocking a steady Ca(2+)-dependent K(+) current it was 36 microM. The bicuculline-sensitive voltage-gated K(+) current was composed of 4-AP-sensitive and 4-AP-resistant components with different kinetic properties. No component of the purely voltage-gated K(+) current was affected neither by 100 nM alpha-dendrotoxin nor by 100 nM I-dendrotoxin. The possible K(+)-channel subtypes mediating the bicuculline-sensitive current in MPN neurons are discussed.
Place, publisher, year, edition, pages
2004. Vol. 46, no 2, 285-95 p.
Animals, Bicuculline/chemistry/*pharmacology, Cells; Cultured, Dose-Response Relationship; Drug, Male, Membrane Potentials/drug effects/physiology, Neurons/*drug effects/physiology, Potassium Channel Blockers/chemistry/*pharmacology, Potassium Channels; Voltage-Gated/*antagonists & inhibitors/physiology, Preoptic Area/*drug effects/physiology, Rats, Rats; Sprague-Dawley
IdentifiersURN: urn:nbn:se:umu:diva-12598PubMedID: 14680766OAI: oai:DiVA.org:umu-12598DiVA: diva2:152269