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The functional role of a bicuculline‐sensitive Ca 2+ ‐activated K + current in rat medial preoptic neurons
Author(s) -
Johansson Staffan,
Druzin Michael,
Haage David,
Wang MingDe
Publication year - 2001
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2001.0625e.x
Subject(s) - apamin , bicuculline , charybdotoxin , chemistry , reversal potential , biophysics , picrotoxin , membrane potential , electrophysiology , tetraethylammonium , gabaa receptor , channel blocker , neuroscience , patch clamp , medicine , potassium channel , biology , biochemistry , receptor , calcium , potassium , organic chemistry
1 A Ca 2+ ‐activated K + current was identified in neurons from the rat medial preoptic nucleus. Its functional role for the resting potential and for impulse generation was characterised by using the reversible blocking agent bicuculline methiodide. Acutely dissociated neurons were studied by perforated‐patch recordings. 2 The effect of bicuculline methiodide was investigated under voltage‐clamp conditions to clearly identify the current affected. At membrane potentials > ‐50 mV, bicuculline methiodide rapidly (< 1 s) and reversibly blocked a steady outward current. Half‐saturating concentration was 12 μ m . The current amplitude increased with potential in the range ‐50 to 0 mV. 3 The bicuculline‐sensitive current was identified as an apamin‐sensitive, Ca 2+ ‐dependent K + current. It was neither affected by the GABA A receptor blocker picrotoxin (100 μ m ) nor by a changed pipette Cl − concentration, but was affected by substitution of extracellular K + for Na + . The current was dependent on extracellular Ca 2+ and was sensitive to 1 μ m apamin but not to 200 n m charybdotoxin. 4 A role for the Ca 2+ ‐dependent K + current in setting the resting potential and controlling spontaneous firing frequency was observed under current‐clamp conditions. Bicuculline methiodide (100 μ m ) induced a positive shift (5 ± 1 mV; n = 18 of resting potential in all neurons tested. In the majority of spontaneously firing neurons, the firing frequency was reversibly affected, either increased or decreased depending on the cell, by bicuculline methiodide.