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Nicergoline inhibits T‐type Ca 2+ channels in rat isolated hippocampal CA1 pyramidal neurones
Author(s) -
Takahashi Kazuyoshi,
Akaike Norio
Publication year - 1990
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1990.tb14079.x
Subject(s) - nicardipine , chemistry , voltage dependent calcium channel , patch clamp , reversal potential , hippocampal formation , l type calcium channel , biophysics , membrane potential , electrophysiology , extracellular , diltiazem , voltage clamp , inhibitory postsynaptic potential , calcium , endocrinology , medicine , biology , biochemistry , organic chemistry
1 The effects of nicergoline on the T‐ and L‐type Ca 2+ currents in pyramidal cells freshly isolated from rat hippocampal CA1 region were investigated by use of a ‘concentration‐clamp’ technique. The technique combines a suction‐pipette technique, which allows intracellular perfusion under a single‐electrode voltage‐clamp, and rapid exchange of extracellular solution within 2 ms. 2 T‐type Ca 2+ currents were evoked by step depolarizations from a holding potential of −100 mV to potentials more positive than −70 to −60 mV, and reached a peak at about −30 mV in the current‐voltage relationship. Activation and inactivation of T‐type Ca 2+ currents were highly potential‐dependent. 3 Nicergoline and other Ca 2+ antagonists dose‐dependently blocked the T‐type Ca 2+ channel with an order of potency nicardipine > nicergoline > diltiazem. 4 The L‐type Ca 2+ channel was also blocked in the order nicardipine > nicergoline > diltiazem, although the T‐type Ca 2+ channel was more sensitive to nicergoline. 5 The inhibitory effects of nicergoline and nicardipine on the T‐type Ca 2+ current were voltage‐, time‐, and use‐dependent, and the inhibition increased with a decrease in the external Ca 2+ concentration. Diltiazem showed only a use‐dependent block.