Enhancement in activities of large conductance calcium-activated potassium channels in CA1 pyramidal neurons of rat hippocampus after transient forebrain ischemia.
Brain Res
; 884(1--2): 147-54, 2000 Nov 24.
Article
em En
| MEDLINE
| ID: mdl-11082496
ABSTRACT
It has been reported previously that the neuronal excitability persistently suppresses and the amplitude of fast afterhyperpolarization (fAHP) increases in CA1 pyramidal cells of rat hippocampus following transient forebrain ischemia. To understand the conductance mechanisms underlying these post-ischemic electrophysiological alterations, we compared differences in activities of large conductance Ca(2+)-activated potassium (BK(Ca)) channels in CA1 pyramidal cells acutely dissociated from hippocampus before and after ischemia by using inside-out configuration of patch clamp techniques. (1) The unitary conductance of BK(Ca) channels in post-ischemic neurons (295 pS) was higher than that in control neurons (245 pS) in symmetrical 140/140 mM K(+) in inside-out patch; (2) the membrane depolarization for an e-fold increase in open probability (P(o)) showed no significant differences between two groups while the membrane potential required to produce one-half of the maximum P(o) was more negative after ischemia, indicating no obvious changes in channel voltage dependence; (3) the [Ca(2+)](i) required to half activate BK(Ca) channels was only 1 microM in post-ischemic whereas 2 microM in control neurons, indicating an increase in [Ca(2+)](i) sensitivity after ischemia; and (4) BK(Ca) channels had a longer open time and a shorter closed time after ischemia without significant differences in open frequency as compared to control. The present results indicate that enhanced activity of BK(Ca) channels in CA1 pyramidal neurons after ischemia may partially contribute to the post-ischemic decrease in neuronal excitability and increase in fAHP.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Canais de Potássio
/
Traumatismo por Reperfusão
/
Isquemia Encefálica
/
Células Piramidais
/
Sinalização do Cálcio
/
Hipocampo
Limite:
Animals
Idioma:
En
Revista:
Brain Res
Ano de publicação:
2000
Tipo de documento:
Article