Amperometry combined with electrophysiological measurements
The detection of released substances from cells as oxidation current at carbon fiber electrodes is often directly combined with electrical measurements from cells. In the following we describe two typical measuring configurations.
Amperometry combined with whole-cell patch clamp recordings
Most suitable for this measurement is an EPC 10 USB Double patch clamp amplifier with standard headstages (potential range +/- 1V).
To headstage 1 you connect the patch pipette and you plug the bath electrode (gnd) to
the ground connector of headstage 1. To headstage 2 you connect the carbon fiber
electrode using the microelectrode holder. The headstage 2 uses the same ground
as headstage 1. No connection from the bath electrode to the ground plug of headstage
2 has to be made. The ground lines are connected internally. Please note that the
recording mode for amplifier 2 must be set to "whole-cell" in order to match the
potential sign conventions typically used for electrochemical measurements.
Patch-Amperometry combined with on-cell Cm measurements
Here we just make a seal with the patch pipette, we work in on-cell mode. The membrane
capacitance can be measured with the software Lock-In and at the same time we can
detect the substances released from the membrane area of the patch with the carbon
fiber electrode placed inside the patch pipette.
Most suitable for this measurement is an EPC 10 USB Double patch clamp amplifier with
a Patch-Amperometry headstage as second probe.
Connect the headstage 1 to a Ag/AgCl electrode placed in the bath. The carbon fiber
electrode is connected to headstage 2. A Ag/AgCl electrode placed inside the patch
electrode serves as bath electrode (ground). With the patch amperometry headstage it
is possible to connect the shield of the BNC connector of the headstage to the ground
of the amplifier.