Voltage clamp 2012 - Hebrew University of Jerusalemoctopus.huji.ac.il/course/Lectures/BennyLecture_VC.2012.pdfA Vout X X1 Vcommand voltage follower Rc RI-elec RV-elec in diff Im amp

Current clamp Voltage clamp

voltage command

current command

1

dt

dvCII

CVQ

im +=

=

IC

R

C

IR

Im

AVout

+

-X

X1

Vcommand voltage follower

Rc

RI-elec

RV-elecin

diff ampIm

cm R

VI =

( )

( )

AwhenVVA

RRI

A

AVV

AVAVRRI

VVVARRI

VVRRI

VVAV

comm

Icmcomm

mcomIcm

mmcomIcm

moutIcm

mcomout

>>≈

+

+−

+=

−−=+

−−=+

−=+

−=

11

)(

1

)1()(

)(

)(

Vholding

clamping amplifier

pulse generator

current measurement

2

Vm

outRseries

A

CR mIc =τ

Clamping time-constant

בידוד זרמים יוניים) 1מניעת שינוי מתח ממברנה) 2קיבוע מתח דינאמי) 3

CmRm Vm

dvCII

CVQ

+=

=

Current clamp Voltage clamp

3

dtCII im +=

A

CR mIc =τ

4

Discontinues single electrode voltage-clamp

5

Continues single electrode voltage clampR (electrode) <<< R (cell)

6

( )smss EVgI −=

7

8

9

10

K

KK

Na

NaNa

EE

Ig

EE

Ig

−=

−=

11

12

k = 24 mV z=1; 24mV e-fold change in P open example: gNa e-fold per 4mV zg = 24/4=6 e

)exp(kT

eEzw

C

O g−−=

13

“1-n” nβn

αn

τn = 1/(αn+βn)

n∞= αn /(αn+βn)

n(t) = n(∞) ( - n(∞) - n(0)) exp (-t/ τn )

4ngg KK =hmgg NaNa3=

14

15

Dynamic clamp