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Guide to Electrophysiological Recording
MultiClamp 700A Theory and Operation, Copyright 2000, 2001 Axon Instruments, Inc.
General Advice
Chamber Design
The tissue chambers used in many
in vitro
electrophysiological experiments usually
have four main requirements:
•
a perfusion system for keeping the tissue alive and applying drugs
•
a method for keeping the tissue mechanically stable
•
optical properties suitable for observing the tissue and positioning
electrodes
•
an electrically stable bath (reference) electrode
Perfusion
Normally the external solution used in
in vitro
experiments is a pH-buffered
salt solution that mimics the extra- or intracellular composition of the cells
under study. Sometimes the solution is bubbled with CO
2
(to maintain the pH
of bicarbonate-buffered solutions) and/or O
2
(to maintain the metabolic
viability of the cells). Some cells (
e.g.
those in retinal slices) have unusually
high metabolic rates and require fast perfusion with high-O
2
solution to remain
viable. Other cells (
e.g.
neurons in dissociated cell culture) may not need any
perfusion or bubbling at all. Because the health of the cells is the single most
important factor in determining the success of your experiments, it is worth
spending some time establishing the optimal conditions for cell survival.
Mechanical Stability
Patch clamp recordings can be surprisingly robust in the presence of
vibrations. However, sharp microelectrode recordings are not so robust in the
presence of vibrations. Neither type of experiment is tolerant of large drifts in
the tissue or electrode that tend to pull the electrode out of the cell. For this
reason, it is important to use a good, drift-free micromanipulator for the
electrode, and to secure the tissue or cells in the chamber so they cannot move
