Korean J Physiol Pharmacol.
1999 Dec;3(6):547-554.
Role of K+ channels to resting membrane potential of rabbit middle
cerebral arterial smooth muscle cells
- Affiliations
-
- 1Department of Physiology, College of Medicine, Inje University, Pusan, Korea.
- 2Department of Neurosurgery, College of Medicine, Inje University, Pusan 614-735, Korea.
Abstract
-
The aim of the present study is to investigate the contribution of
Ca2+-activated K+ (KCa) channels and delayed rectifier K+ (KV) channels
to the resting membrane potential (RMP) in rabbit middle cerebral
arterial smooth muscle cells. The RMP and membrane currents were
recorded using the whole-cell patch configuration and single KCa
channel was recorded using the outside-out patch configuration. Using
the pipette solution containing 0.05 mM EGTA, the RMP was -25.76+/-5.08
mV (n=12) and showed spontaneous transient hyperpolarizations (STHPs).
The membrane currents showed time- and voltage-dependent outward
currents with spontaneous transient outward currents (STOCs). When we
recorded the membrane potential using the pipette solution containing
10 mM EGTA, the RMP was depolarized and did not show STHPs. The
membrane currents showed no STOCs but only showed slowly inactivating
outward currents. External TEA (1 mM) reversibly inhibited the STHPs,
depolarized the RMP, reduced the membrane currents, abolished STOCs,
and decreased the open probability of single KCa channel. When KV
currents were isolated, the application of 4-AP (5 mM) depolarized the
RMP. The important aspect of our results is that KCa channel is
responsible for the generation of the STHPs in the membrane potential
and plays an important role in the regulation of the RMP and KV channel
is also responsible for the regulation of the RMP in rabbit middle
cerebral arterial smooth muscle cells.