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Strychnine‐induced potassium current in isolated dorsal root ganglion cells of the rat
Author(s) -
Aibara K.,
Oonuma M.,
Akaike N.
Publication year - 1991
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.1476-5381.1991.tb12199.x
Subject(s) - extracellular , reversal potential , chemistry , biophysics , bicuculline , patch clamp , dorsal root ganglion , strychnine , membrane potential , electrophysiology , potassium , intracellular , anatomy , medicine , dorsum , biochemistry , gabaa receptor , biology , receptor , organic chemistry
1 Effects of strychnine (Str) on the dissociated dorsal root ganglion (DRG) cells of the rat have been investigated in whole‐cells configuration by a conventional patch‐clamp technique. 2 γ‐Aminobutyric acid (GABA)‐induced Cl − current ( I Cl ) increased sigmoidally with increasing concentration. The half‐maximal response ( K a ) was 3 × 10 −5 m and the Hill coefficient was 1.5. Both Str and bicuculline inhibited the GABA‐induced I Cl in a concentration‐dependent manner. 3 Str itself could elicit the current at concentrations over 10 −5 m , at which concentrations the GABA response was completely suppressed. The concentration‐response curve for the Str‐induced current was bell‐shaped, and a nearly maximum response occurred at 3 × 10 −4 m . A transient ‘hump’ current appeared immediately after the wash‐out of external solution containing high concentrations of Str over 3 × 10 −4 m . 4 The Str‐induced outward current and a transient ‘hump’ current were augmented by the removal of extracellular K + and were suppressed by the substitution of intracellular K + for Cs + . But the current was not sensitive to extracellular Na + , Ca 2+ and Cl − . 5 The reversal potential of Str‐induced current ( E Str ) was −75 mV, which was close to the K + equilibrium potential ( E K = −76.3 mV). The change of E Str for a ten fold change in extracellular K + concentration was 58 mV, indicating that the membrane behaves like a K + electrode in the presence of Str. The reversal potential of the ‘hump’ current was also close to E K . 6 The Str‐induced outward current was antagonized by K + channel blockers such as Ba 2+ , tetraethylammonium (TEA)‐chloride, and 4‐aminopyridine (4‐AP) in a concentration‐dependent manner. 7 The Str‐induced K + current was not affected by internal perfusion of bis (γ‐aminophenoxy)ethane‐ N,N,N′,N ‐tetraacetic acid (BAPTA), indicating that the Str response does not result in the activation of K + conductance by the intracellular Ca 2+ .