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α 2 ‐Adrenoceptor‐mediated potassium currents in acutely dissociated rat locus coeruleus neurones
Author(s) -
Arima Junichi,
Kubo Chiharu,
Ishibashi Hitoshi,
Akaike Norio
Publication year - 1998
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.1469-7793.1998.057br.x
Subject(s) - locus coeruleus , prazosin , chemistry , medicine , endocrinology , agonist , patch clamp , antagonist , biophysics , potassium channel , gtp' , reversal potential , intracellular , electrophysiology , biology , receptor , central nervous system , biochemistry , enzyme
1 The noradrenaline (NA)‐activated response was investigated in neurones acutely dissociated from the rat locus coeruleus (LC) using nystatin‐perforated, conventional whole‐cell and inside‐out patch recording modes under current‐ and voltage‐clamp conditions. 2 Under current‐clamp conditions, NA hyperpolarized the LC neurones, abolishing the spontaneous action potentials. In voltage‐clamp studies, NA induced an inwardly rectifying K + current ( I NA ) in a concentration‐dependent manner with a half‐maximum effective concentration of 2.2 × 10 −7 M. 3 INA was mimicked by the α 2 ‐agonist UK14304 but was inhibited by either the α 2B /α 2C antagonist ARC239 or the α 1 ‐ and α 2B /α 2C antagonist prazosin, suggesting the contribution of α 2B /α 2C adrenoceptors. 4 INA was inhibited by the intracellular application of GDPβS but fully activated by intracellular perfusion of GTPγS. 5 In the inside‐out recording mode, the application of GTP to the cytoplasmic side of the patch membrane markedly enhanced the open probability of the NA‐activated single channels which represented the inwardly rectifying properties. 6 These results indicate that the activation of α 2B /α 2C adrenoceptors coupled with GTP‐binding protein directly activates the inwardly rectifying K + currents in rat LC neurones, thus resulting in a decrease in the spontaneous firing activities.