44
•
Guide to Electrophysiological Recording
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 very far. Tissue slices are
MultiClamp 700B Theory and Operation, Copyright 2005 Axon Instruments / Molecular Devices
