title: Strychnine-induced potassium current in isolated dorsal root ganglion cells of the rat.
abstract: 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. gamma-Aminobutyric acid (GABA)-induced Cl- current (ICl) increased sigmoidally with increasing concentration. The half-maximal response (Ka) was 3 x 10(-5) M and the Hill coefficient was 1.5. Both Str and bicuculline inhibited the GABA-induced ICl 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 x 10(-4) M. A transient 'hump' current appeared immediately after the wash-out of external solution containing high concentrations of Str over 3 x 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+, Ca2+ and Cl-. 5. The reversal potential of Str-induced current (EStr) was -75 mV, which was close to the K+ equilibrium potential (EK = -76.3 mV). The change of EStr 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 EK. 6. The Str-induced outward current was antagonized by K+ channel blockers such as Ba2+, 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(gamma-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 Ca2+.
authors.affiliation: Department of Neurophysiology, Tohoku University School of Medicine, Sendai, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Aibara
authors.forename: M
authors.initials: M
authors.lastname: Oonuma
authors.forename: N
authors.initials: N
authors.lastname: Akaike
mesh_terms: D000818:Animals; D001464:Barium / Q000494:pharmacology; D001640:Bicuculline / Q000494:pharmacology; D004594:Electrophysiology; D005727:Ganglia, Spinal / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D066298:In Vitro Techniques; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013331:Strychnine / Q000494:pharmacology*; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
chemical_list: D015221:Potassium Channels; D001464:Barium; D005680:gamma-Aminobutyric Acid; D013331:Strychnine; D011188:Potassium; D001640:Bicuculline