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Molecular determinants of Ca 2+ ‐dependent K + channel function in rat dorsal vagal neurones
Author(s) -
Pedarzani Paola,
Kulik Anna,
Müller Michael,
Ballanyi Klaus,
Stocker Martin
Publication year - 2000
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.1469-7793.2000.t01-1-00283.x
Subject(s) - dorsum , chemistry , function (biology) , biophysics , neuroscience , physics , anatomy , biology , microbiology and biotechnology
1 Using in situ hybridisation histochemistry in combination with patch‐clamp recordings and specific pharmacological tools, the molecular nature of the channels underlying Ca 2+ ‐dependent K + currents was determined in dorsal vagal neurones (DVNs) of rat brainstem slices. 2 In situ hybridisation analysis at cellular resolution revealed the presence of ‘big’‐conductance Ca 2+ ‐ and voltage‐activated K + (BK) channel α‐subunit mRNA, and of only one ‘small’‐conductance Ca 2+ ‐activated K + (SK) channel subunit transcript, SK3, at very high levels in DVNs. By contrast, SK1 and SK2 mRNAs were below the threshold limit of detection. 3 The SK channel‐mediated after‐hyperpolarising current ( I AHP ) was blocked by apamin with a half‐maximal inhibitory concentration of ∼2.2 n m . This is consistent with homomultimeric SK3 channels mediating I AHP in DVNs. I AHP was also blocked by scyllatoxin (20–30 n m ) and curare (100–200 μ m ). 4 Application of apamin (100 n m ) or scyllatoxin (20 n m ) invariably caused a substantial increase to 146.1 ± 10.4 and 181.8 ± 12.9 % of control, respectively, in the spontaneous firing rate of DVNs. Action potential duration was not affected by these SK channel blockers. 5 The selective BK channel blocker iberiotoxin (50 n m ) increased action potential duration by 22.5 ± 7.3 %, as did low concentrations of tetraethylammonium (0.5 m m ; 99.3 ± 16.4 %) and the Ca 2+ channel blocker Cd 2+ (100 μ m ; 49.5 ± 20.9 %). BK channel blockade did not significantly affect the firing rate of DVNs. 6 These results allow us to establish a tight correlation between the properties of cloned and native BK and SK channels, and to achieve an understanding, at the molecular level, of their role in regulating the spontaneous firing frequency and in shaping single action potentials of central neurones.