User
Guide
for
Axoclamp
900A
Hyperpolarization
A
negative
shift
in
V
m
.
Axoclamp
Polarity
Conventions
The
conventions
described
here
apply
to
all
amplifiers
manufactured
by
Molecular
Devices.
To
prevent
confusion,
Molecular
Devices
always
uses
current
and
voltage
conventions
based
on
the
instrument’s
perspective.
That
is,
the
current
is
defined
with
respect
to
the
direction
of
flow
into
or
out
of
the
headstage.
Molecular
Devices
amplifiers
do
not
have
switches
that
reverse
the
current
or
the
voltage
command
polarities.
This
prevents
forgetting
to
move
the
switch
to
the
correct
position.
The
data
are
recorded
unambiguously
and
the
correct
polarity
can
be
determined
during
subsequent
data
analysis.
Positive
Current
Current
that
flows
out
of
the
headstage
into
the
electrode
and
out
of
the
electrode
tip
into
the
cell.
Positive/Negative
Potential
A
positive/negative
voltage
at
the
headstage
input
with
respect
to
the
bath
ground.
With
these
definitions
it
is
easy
to
work
out
the
correct
polarity
for
every
recording
configuration.
For
example,
in
the
whole
‐
cell
or
outside
‐
out
patch
configuration
the
electrode
tip
is
on
the
intracellular
face
of
the
cell.
Thus,
a
negative
potential,
V
p
,
at
the
headstage
input
(=electrode
interior)
is
a
negative
potential
inside
the
cell.
The
cell’s
membrane
potential
under
voltage
clamp
is
therefore
V
m
=
V
in
–
V
out
=
V
p
–
0
=
V
cmd
.
Positive
current
flowing
out
of
the
electrode
must
then
flow
from
the
inside
to
the
outside
surface
of
the
cell,
which
means
that
it
is
outward
current.
194
