1. potassium channel function: 1.shape action potentials and set the resting membrane potential 2....
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1. Potassium channel
Function:1.shape action potentials and set
the resting membrane potential 2. maintaining vascular tone 3. secretion of hormones 4. ion transport
Types
Voltage-gated potassium channel Inwardly rectifying potassium channel resting potassium channels" or "leak channels Calcium-activated potassium channel
6TM: The voltage-gated K+ channels
Kv, KCNQ, Kca2+
A-type currrent
M-current
2-TM. The inward rectifier K+
KIR1.x, KIR2.x, KIR3.x, KIR4.x,
KIR5.x, KIR6.x and KIR7.x
4-TM. Sensitive to halothane,insensitive to TEA and 4-APRegulate cell volume
2. Cell recording solutions and Protocol for Ca2+ 、 Na+ 、 K+
(1) Calcium channels and Protocol
激活曲线 Protocol
失活曲线稳态失活曲线
失活后再激活曲线
( 2 ) Sodium channel
Protocol
( 3 ) Potassium channel
① Inwardly rectifying potassium channel(KIR)
激活方案
②The delayed rectifier current (IK)
largely responsible for repolarization and consists of two components namely IKs and IKr.
Voltage-Time dependent activation
IKtail
Time dependent activation
IKtail
ms
0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200
mV
-100
-80
-60
-40
-20
0
20
40
60
controldrugwash out
豚鼠心室肌细胞
③ KATP
KATP
βcellSmooth muscle cells
inside-out patch. The pipette potential is -100 mV
Whole cell recording,With ATP and GDP in the pipette solution, Vh-60
inside-out patch
Inside out-recording(-100mv)Bath solution (for the intracellular side of the membrane) included (mM): KCl 120, KOH 20, MgCl2 1, EGTA 5, Hepes 10, glucose 5, Na2ATP 0.3, and MgADP 0.5 (pH=7.2); while pipette solution (for the extracellular side of the membrane) contained (mM): KCl 140, MgCl22, EGTA 2, glucose 10, and Hepes 10 (pH=7.4).
Why Vh-60?Answer:minimize Kca
Whole cell-recordingThe bath solution contained (mM):NaCl 140, KCl 5.4, MgCl2 1.2, HEPES 10, EGTA 2, glucose 10 (pH adjusted to 7.4 with NaOH). The pipette solution comprised (mM): KCl 140, MgCl2 1, EGTA 10, HEPES 10, glucose 5, Na2ATP 0.3, and MgADP 0.5 (pH=7.2)
The membrane potential recordingThe bath solution contained (mM):NaCl 140, KCl 5.4, MgCl2 1.2, HEPES 10, EGTA 2, glucose 10 (pH adjusted to 7.4with NaOH). The pipette solution comprised (mM): KCl 140, MgCl2 1, EGTA 10,HEPES 10, glucose 5, nystatin 250 μg/ml
④ IK,M------(KCNQ2-KCNQ3)
the M-current characterized as a low-threshold, voltage-gated K+ current that is active around the resting membrane-potential and constitutes an important regulator of neuronal excitability
a voltage-and time-dependent, low-threshold, slowly activating current.
Traditional M-currentvoltage-clamp protocol: holding potential was -30 mV; step potentials were -40 to -80 mV
Activation from a holding potential of -60 mV in 5 mV increments.
IKM tail
0.3 nA, 200-ms current-pulse injection
M- current
Predominant K+ current in many mature neurons that is initially activated at the subthreshold range of membrane potential and deactivated during depolarizing pulses of duration.
⑤Transient inactivating A-type current (IA)
50ms
14 (A1 ), 10 (A2 ), or 30 (A3 ) pA for 800 ms
⑥ Kca
BKSKIK
voltage gated and calcium modulated
NATURE 2004,427(26)
voltage-clamped at-30mV and pulsed for 400 ms from-100mV to +140mV For the perforated-patch experiments, a stock solution of 100 mg/ ml amphotericin B and final concentration of 200 mg/ml amphotericin The pipette solution contained (in mM): 140 KCl, 10 NaCl, 2 MgCl2, 0.7 CaCl2,1 EGTA and 10 HEPES (made to pH 7.3 with KOH). Cells were perfused with anextracellular buffer containing (in mM): 140 NaCl, 2.5 KCl, 0.5 MgCl2, 1.2 CaCl2,101 HEPES and 5 glucose (made to pH 7.4 with NaOH).
Journal of physiology
a holding potential of –70 mV to test potentials between –50 and +80 mV in 10-mV increments.
To obtain steady-state KCa channel measurements in perforated patch-clamp experiments, Ca2+ sparks and thus transient KCa currents were abolished using thapsigargin (100 nM), an inhibitor of sarcoplasmic reticulum Ca2+-ATPase
the bathing solution contained (in mM) 134 NaCl, 6 KCl, 2 CaCl2, 1 MgCl2, 10 HEPES, and 10 glucose (pH 7.4, NaOH). The perforated-patch pipette solution contained (in mM) 110 potassium aspartate, 30 KCl, 10 NaCl, 1 MgCl2, 10 HEPES, and 0.05 EGTA (pH 7.2 with KOH). Amphotericin B (1 μg/ml)
For inside-out recordings, the pipette solution contained (in mM) 140 NaCl, 6 KCl, 10 HEPES, 1 CaCl2, and 2 MgCl2. The inside-out bath solution contained (in mM) 140 KCl, 10 HEPES, 2 MgCl2, 5 or 1 EGTA, 1.6 HEDTA, and appropriate amounts of CaCl2 to obtain free Ca2+ concentrations of 0.1, 0.3, 1, 3, 10, 30, or 100 μM.