Multichannel Systems HiClamp Manual - Manual (Page 73)

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10 TEVC Recording Background
10.1 TEVC Recording Background
About TEVC Recording with the HiClamp
The small-sized digital TEVC amplifier is integrated within the HiClamp and fully computer-
controlled. It operates either in true current clamp or voltage clamp mode and uses a PI
(Proportional Integral) based technique. The ClampAmpC records up to ± 105 μA of current,
and the 16-bit A/D-conversion together with the over-sampling method results in an overall
resolution of 1 nA. The sampling frequency of up to 20 kHz guarantees high-performance data
acquisition of fast signals. The ClampAmpC features a short rise time of less than 500 μs, suitable
even for recording from fast sodium channels.
The recording sequences can be flexibly designed exactly to your requirements. Raw data can be
reviewed and evaluated offline with the HiClamp software, and also exported to custom analysis
software.
Preparations for Recording
Recording with the HiClamp is easy, but nevertheless, we recommend that you make
a few test recordings with non-injected oocytes and the provided sample recording protocol.
It is also a good idea run a test recording with the test model cell first.
Amplifier settings: Please make sure that the amplifier settings are appropriate for your ion
channel type. For more details, please see section "TEVC Recording - Background". For a first
test, the settings for slow ion channels are fine.
Ion channel kinetics Gain (P Coefficient) Integrator (I Coefficient)
slow 800 100 fast 2000 100
Glass micro electrodes: We recommend using a ready-made glass micro electrodes provided by
Multi Channel Systems, especially for new HiClamp users. You can use custom-built electrodes
as well, but you may observe problems if the design of electrodes does not follow the required
specifications. Please see "Ordering Information" for details.
Electrolyte solution for filling the glass electrodes of the measuring head. Recommended solutions
are 1.5 M KAc, 1 M KCl, pH 7.2 or 3 M KCl. The main disadvantage of a pure KCl solution is the
fast formation of salt crystals that will shorten the lifetime of the electrodes. The KAc/KCl solution
does not tend to crystallize, which is an advantage for storing the measuring head over night.
You may want to vary the KCl concentration of the KAc/KCl solution for optimizing your
experiments. We have used concentrations in a range from 0.1 M to 1 M KCl. Please keep in mind
that the electrode impedance increases with a decreased overall ion concentration in the
electrolyte.
Reusing a TEVC probe
Multi Channel Systems recommends replacing the recording electrodes each time when loading
a new oocyte well plate onto the HiClamp, for achieving best recording results. But in many cases,
a set of electrodes can be reused several times. It is also advisable to check the oocyte quality.
It seems that bad oocytes tend to clog the recording electrodes more easily than oocytes of
a very good quality.
To increase the lifetime of measuring heads, Multi Channel Systems recommends the following:
 Use 1.5 M KAc, 1 M KCl, pH 7.2 as electrolyte for filling the electrodes to avoid crystallization,
which is a known issue with pure KCl solution.
 Use only high-quality oocytes to avoid that membrane residues from non-viable oocytes clog
the electrode tips.