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. 1992 Aug;106(4):823–827. doi: 10.1111/j.1476-5381.1992.tb14419.x

Strychnine-induced potassium current in CA1 pyramidal neurones of the rat hippocampus.

S Ebihara 1, N Akaike 1
PMCID: PMC1907660  PMID: 1356568

Abstract

1. Direct actions of strychnine (Str) and brucine (Bru) on the dissociated hippocampal CA1 neurones of the rat have been investigated with the whole-cell mode of the patch-clamp technique. 2. At a holding potential (VH) of -20 mV, both Str and Bru elicited outward current at concentrations over 10(-5) M. The reversal potential of Str-induced current (EStr) was -77.8 mV, which was close to the K+ equilibrium potential (EK = -80.3 mV). The change in 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. 3. The concentration-response curves for Str and Bru were bell-shaped, and nearly maximum response occurred at 10(-4) M for Str and 3 x 10(-4) M for Bru. The maximum current amplitude induced by Bru was about 80% of that induced by Str. A transient 'hump' current appeared immediately after the wash-out of external solutions containing Str and Bru at concentrations higher than 10(-4) and 3 x 10(-4) M, respectively. 4. The Str-induced current (IStr) was antagonized by K+ channel blockers such as Ba2+, tetraethylammonium (TEA)-chloride, and 4-aminopyridine (4-AP) in a concentration-dependent manner. IStr was insensitive to glibenclamide, a blocker of ATP-sensitive K+ channels. 5. Internal perfusion with 10 mM BAPTA did not affect the Str-induced IK. Depletion of the intracellular Ca2+ store by caffeine had no effect, indicating that intracellular Ca2+ does not mediate the Str-induced activation of K+ conductance.(ABSTRACT TRUNCATED AT 250 WORDS)

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Selected References

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