Jm. Mienville et Jr. Clay, EFFECTS OF INTRACELLULAR K-ACTIVATED K+ CHANNELS( AND RB+ ON GATING OF EMBRYONIC RAT TELENCEPHALON CA2+), Biophysical journal, 70(2), 1996, pp. 778-785
We have investigated the effects of intracellular K+ and Rb+ on single
-channel currents recorded from the large-conductance Ca+2-activated K
+ (BK) channel of the embryonic rat telencephalon using the inside-out
patch-clamp technique, Our novel observation concerns the effects of
these ions on rapid flickering of channel openings, Specifically, flic
ker gating was voltage dependent, i.e., it was reduced by depolarizati
on in the -60 to -10 mV range with equimolar concentrations of K+ ions
(150 K-0(+)/150K(i)(+)). Removal of K-i(+) resulted in significant fl
ickering at all potentials in this voltage range, In other words, the
voltage dependence of flicker gating was effectively eliminated by the
removal of K-i(+). This suggests that a K+ ion entering the channel f
rom the intracellular medium binds, in a voltage-dependent manner, at
a site that locks the flicker gate in its open position, No effects of
changes in K-i(+) were observed on the primary, voltage-dependent gat
e of the channel, The change in flickering did not cause a change in t
he mean burst duration, which indicates that the primary gate is stoch
astically independent of the flicker gate. Intracellular Rb+ can subst
itute for-and is even more effective than-K-i(+) with regard to suppre
ssion of flickering. Substitution of Rb-i(+) for K-i(+) also increased
the mean burst duration for V greater than or equal to -30 mV. Both e
ffects of Rb-i(+) were removed by membrane hyperpolarization.