Because the experiment relies on the
integrity of the muscle membrane, great care should be exerted during
The abdomen of the crayfish is dissected out. The dorsal extensor
muscles are used in this experiment.
Cut along the abdomen (tail)
on each side and on top; using forceps, tear the upper part of the
abdomen from the much larger and lower musculature. The dorsal extensor
muscles separate readily from the larger ventral mass of flexor muscles.
Although both ventral and dorsal parts can be used, it is preferable to
keep the upper part of the abdomen to record potentials.
A glass microelectrode is
selected, taking special care not to touch the tip. (These
microelectrodes are made from capillary tubes heated in the middle and
pulled mechanically to a fine tip. They are then filled with 3 M KCl.)
The glass microelectrode is
placed in the holder of the micromanipulator. An Ag/AgCl wire is
inserted into the microelectrode. A reference Ag/AgCl electrode is
placed directly into the Ringer's solution in the bath. Both electrodes
are connected to the amplifier.
Pin the dorsal part of the tail up:
recordings will be made with the superficial extensor muscles.
As the experiment will be
performed using bath solutions with different concentrations, it will be
necessary to aspirate an old solution out of the chamber with a syringe,
in preparation for a new bath solution.