Guide to Electrophysiological Recording • 35
Chapter 4
Computer Noise
Digital computers can generate considerable electrical noise, both via the
power ground and via radiative interference from the monitor. For optimal
noise performance of the MultiClamp 700A, careful attention should be paid to
the placement of the computer. For example, the monitor should not be placed
immediately above or below the MultiClamp 700A in the instrument rack.
Other advice on noise reduction is given in the
NOISE section of Chapter 5.
Patch Clamping
The patch clamp technique enables stable, low-resistance access to the interior of many
cell types. Once this access is established, it is up to the experimenter, of course,
whether to record in V-Clamp or I-Clamp mode. However, the discussion in this Part
will assume that V-Clamp mode is being used, at least for the initial steps of seal
formation and gaining whole-cell access. Once in the whole-cell configuration, you
can switch to I-Clamp mode. Advice on recording in I-Clamp mode is given in the
following section, “Sharp Microelectrode Recording”.
Headstage and Holder Considerations
Ensure the headstage is securely attached to the micromanipulator using one of the
mounting plates on the headstage case. Before attaching the pipette holder, or
inserting a pipette in the holder, be sure to touch grounded metal to discharge any static
charge that may have inadvertently built up on you or on the holder. Attach a piece of
flexible tubing to the suction port on the side of the holder, arranging the tubing in
such a way that it will not pull on the holder, even if you unintentionally tug on the
tubing while applying suction.
Before using the holder in a real experiment, check for leaks. Insert an unfilled patch
pipette in the holder, apply moderate suction by mouth, and then allow the end of the
tube to seal against your upper lip. The tube should remain stuck to your lip
indefinitely, were you prepared to wait. If it falls off in a few seconds, check that the
cone-washers (or O-rings) in the holder are tight.
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