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PRINCIPLES OF OPERATION
Axopatch 200B, Copyright 1997-1999, Axon Instruments, Inc.
through the pipette, across the patch membrane from the outside surface to the
inside surface. Therefore a positive current is inward.
Outside-Out Patch
In outside-out patch mode, the membrane patch is detached from the cell in such a
way that the surface that was originally the outside surface remains exposed to the
bath solution. The potential on the outside surface is 0 mV (bath potential). The
pipette interior is connected to what was originally the inside surface of the
membrane. A positive command voltage causes the transmembrane potential to
become less negative, therefore it is depolarizing. For example, to approximate
resting membrane conditions, assuming that V
m
= -70 mV, the potential inside the
pipette must be adjusted to -70 mV. If the potential inside the pipette is then
increased from -70 mV to -50 mV, the transmembrane potential of the patch
depolarizes from -70 mV to -50 mV.
The membrane potential changes directly with the command potential. A positive
pipette current flows through the pipette, across the patch membrane from the
inside surface to the outside surface. Therefore a positive current is outward.
Summary
1) Positive current corresponds to:
Cell-attached patch patch inward current
Inside-out patch patch inward current
Outside-out patch patch outward current
Whole-cell voltage clamp outward membrane current
Whole-cell current clamp outward membrane current
2) A positive shift in the command potential is:
Cell-attached patch hyperpolarizing
Inside-out patch hyperpolarizing
Outside-out patch depolarizing
Whole-cell voltage clamp depolarizing
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