Analysis of membrane behavior: Voltage and Patch Clamps- Lecture 19 Flashcards
What is the voltage clamp method?
two microelectrodes are inserted into a cell; one to measure Vm, feeding it into a differential amplifier which compares it to user-set command voltage that specifies the value of Vm to be held constant and converts the difference into current, which is passed into the cell through the other (this gives us known I and V, so that g can be calculated)
What does tetrototoxin (TTX) do?
blocks voltage-gated Na+ channels
What does tetraethylammonium (TEA) do?
blocks most K+ channels
What is an IV plot?
a graph of the relationship between current and voltage
What is the patch-clamp method?
analysis at the single-channel level where an electolyte filled glass pipette is pressed against the outside of the cell membrane (containing a small number of channels), forming a tight, high electrical resistance seal with the bilayer; the solution inside the pipette is connected to a feedback amplifier that clamps Vm at the command potential and measures the current needed to do this
What are the different patch configurations?
cell attached, excised (inside-out), and whole-cell
What is cell-attached patch clamping?
the first step in patch clamping that keeps the intracellular environment intact allowing for either of the two other methods to be performed
What is excised (inside-out) patch clamping?
pulling the patch out of the cell while keeping the seal to expose it to different bathing solutions that would mimic the intracellular environment in a way that is easily manipulated
What is whole cell patch clamping?
teh patch is ruptured while the pipette is still attached to the membrane, resulting in the pipette containing a much larger volume of solution than of the cell, dialyzing the interior of the cell so that the cytosol is replaced with pipette solution and macroscopic combined activity of the channels in the intact membrane is recorded
