PC-505B Manual, Rev. 201013
Warner
Instruments
A Harvard Apparatus Company
33
Rupture is signaled by a sudden large increase in
the
TEST PULSE
current when in
voltage clamp
mode,
or as a sudden decrease in
TEST PULSE
voltage at the
V
m
x10 terminal when in
current clamp
mode. Once
the membrane is ruptured, immediately apply a
resting holding potential appropriate to the cell under
study.
An example of a ruptured membrane signal is
shown to the right.
Whole-cell recording - Series R compensation
In single channel recording, the pipette electrode
resistance (RP) is negligible compared to the patch
and seal resistances. However, in whole cell recording
this electrode resistance becomes a significant factor
and will slow the response of the amplifer.
Series R compensation is adjusted by using the
SERIES R
and
C
-
SLOW
controls. The
SERIES
R
control compensates for the resistance of the pipette opening at the cell and the
C
-
SLOW
control compensates for the cell membrane capacitance.
A good adjustment for Series R is important
but can be a subtle operation. A basic approach is
outlined below.
•
Verify that the
TEST PULSE
is active and set to
x0.01.
The trace should appear like the example
to the right.
•
If you
’
ve previously measured the pipette
resistance (RP), then initially set the
SERIES R
dial to this value.
NOTE
: The
SERIES R
control is calibrated to 10 M
/turn, so if your
RP=4.5 M
, then set the dial to 0.45.
•
If you do not know the pipette resistance, then
set the
SERIES R
control to 5.0.
•
Next, turn on
C
-
SLOW
and adjust up until a
slight overshoot appears on the leading edge of
the trace. An example is shown to the right.
