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An osmosensitive voltage‐gated K + current in rat supraoptic neurons
Author(s) -
Zhang Wenbo,
Wang Daoyi,
Liu XiaoHong,
Kosala W.R.A.,
Rajapaksha J.S.,
Fisher Thomas E.
Publication year - 2009
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/j.1460-9568.2009.06772.x
Subject(s) - apamin , channel blocker , chemistry , nifedipine , osmoreceptor , patch clamp , medicine , biophysics , endocrinology , potassium channel , hypothalamus , electrophysiology , biology , calcium
Abstract The magnocellular neurosecretory cells of the hypothalamus (MNCs) regulate their electrical behaviour as a function of external osmolality through changes in the activity of osmosensitive ion channels. We now present evidence that the MNCs express an osmosensitive voltage‐gated K + current (the OKC). Whole‐cell patch‐clamp experiments on acutely isolated MNCs were used to show that increases in the external osmolality from 295 to 325 mosmol/kg cause an increase in a slow, tetraethylammonium‐insensitive outward current. The equilibrium potential for this current is close to the predicted E K in two different concentrations of external K + . The OKC is sensitive to block by Ba 2+ (0.3 m m ), and by the M‐type K + current blockers linopirdine (150 μ m ) and XE991 (5 μ m ), and to enhancement by retigabine (10 μ m ), which increases opening of M‐type K + channels. The OKC is suppressed by muscarine (30 μ m ) and is decreased by the L‐type Ca 2+ channel blocker nifedipine (10 μ m ), but not by apamin (100 n m ), which blocks SK‐type Ca 2+ ‐dependent K + currents. Reverse transcriptase‐polymerase chain reaction and immunocytochemical data suggest that MNCs express several members of the K V 7 (KCNQ) family of K + channels, including K V 7.2, 7.3, 7.4 and 7.5. Extracellular recordings of individual MNCs in a hypothalamic explant preparation demonstrated that an XE991‐ and retigabine‐sensitive current contribute to the regulation of MNC firing. Our data suggest that the MNCs express an osmosensitive K + current that could contribute to the regulation of MNC firing by external osmolality and that could be mediated by K V 7/M‐type K + channels.