1. Potassium channel Function: 1.shape action potentials and set the resting membrane potential 2. maintaining vascular tone 3. secretion of hormones 4.

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.