Multichannel Systems HiClamp Manual - Manual (Page 44)

HiClamp Manual
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A single recording data epoch (or sweep) is defined by its holding voltage -100 mV,
and the number of steps the values of which are indicated in "LoopX" window.
The values above indicate which steps have to be sequentially performed. For example, to record
the activity of a potassium channel it would be necessary to step the voltage between different
values ranging from -50 to + 10 mV starting from a holding potential of -100 mV.
Activation of this voltage protocol would yield a sequence of seven voltage steps ranging from
-50 mV to + 10 mV by increment of 10 mV.
A typical example of currents recorded in a cell expressing a voltage gated potassium channel
in response to a series of voltage steps is shown.
As for ligand-gated channels, data are readily analyzed in DataMining using the cursors, and can
be expressed either as current in function of the voltage step or conductance. Results can be fitted
with Boltzman equation to describe the parameters best representing the channel properties.
Note the small tail current observed at the pulse offset. These data can be further analyzed using
multiple step controls with, for example, a constant activation pulse and a second step of variable
amplitude allowing the determination of the reversal potential. Such “tail current” protocols are
easily implemented using the voltage command window.
Note that the voltage command window also offers the possibility to apply repetitive steps at
regular time intervals.