HHsim Voltage Clamp Controls

Switching to Voltage Clamp mode changes the formats of the main display and the stimulus window. Here is how the main display looks. Notice that the "Stimuli" button along the top row has been replaced by a "VStim" button.

In the figure above, the voltage step (bottom trace) has been run; the resulting current is plotted in the top trace. Plotting is done by pressing the green "Run" button.

Stimulus Patterns

The VStim window defines the voltage clamp stimulus patterns for voltage clamp experiments. A stimulus consists of a baseline voltage and hold time, followed by up to three "steps", each consisting of a voltage and a duration. There are thus a total of eight parameters. All are user-controllable via sliders and editboxes.

Using the VStim controls, one of these parameters can be systematically varied while the rest remain fixed. The parameter to be varied is indicated by the purple pushbutton; in the figure above, it's the step 1 voltage. The editbox at the bottom of the window contains a set of values for this parameter, separated by spaces. Three values can be specified, for example, by typing "-40 -25 -10", without the quotes, in the lower text box.

When the green "Run" button is pressed in the main window, HHsim runs through each of the stimulus curves shown in the VStim window. If you press "Run" again it will generate more curves, of different colors, that overlay the first curve(s). To avoid this, press the "Clear" button in the main window before hitting "Run" again.

If you want to vary more than one stimulus parameter at a time, e.g., changing both the step 1 voltage and duration, you can do so by making the variations manually. Set up your first curve using the sliders, press "Run", then set up your next curve, press "Run" again, and so on. Another trick you can do by not hitting "Clear" is compare the effects of stimuli in the presence vs. absence of a drug. Set up your family of curves and press "Run". Then apply a drug using the Drugs window, and press "Run" again to run through the same stimuli. This will plot another set of lines, with different colors, on top of the first set. A total of eight lines can be plotted.

Back to the Guide to Using HHsim

Dave Touretzky
Last modified: Sun Aug 24 02:25:23 EDT 2008