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Effects of pharmacological blockers on action potential




The below tutorial explains how to use neuron simulator to study the effect of pharmacological blockers on action potential.


For general instructions on usage of neuron simulator, please refer procedure tab in modeling resting potentials.


User instructions:


Step 1: Load simulator by clicking on “Simulator” tab. If you didn’t log in, you will be asked to sign in which in general can be your gmail or yahoo mail id.  




Fig 1: Screenshot of neuron simulator after loading. Arrow pointing to click on “Stimuli” tab. 


Step 2: After logging in and loading simulator, you need to proceed to “Stimuli” tab shown on the right side of the simulator under “Variables” section. Upon clicking on that, you will see a similar appearance as shown in Fig 1. Two different kinds of stimulus options were provided, “Stim1” and “Stim2” as you can see in Fig 2. You can set different stimulus patterns for Stim1 and Stim2 as you can see in Fig 3. If you wish to change the stimulus duration, amplitude and delay, click on the brown circle or dot and drag according to your need. To return back to main simulator window, click on cross mark present on the right top side. 



Fig 2: Cropped image from the screenshot after clicking on “Stimuli” tab. “Stim1” and “Stim2” are two different stimulus patterns.  




Fig 3: Stimulus pattern depicted for Stim1. Likewise you can set for Stim2. Crossmark box denotes that by clicking on it, you can return to the main simulator window. 


Step 3: After setting up your desired stimulus, proceed to “Drugs” tab under the same “Variables” section. On clicking, you will see slider bars to adjust the percentage of TTX and TEA. By default, both drugs are set to 0 (see Fig 4.). Drag the slider bar of either TTX to study the effect of TTX block on action potential or TEA to study its effect on action potential or both. Activate pronase blocker by checking it to study the prevention of sodium inactivation. 


Step 4: After you finished setting up your stimulus and drug concentration, return to the main simulator window. Click run and then “Stim1” or “Stim2” to simulate HH model with the changes you adopted. Repeat the study with different drug concentrations and observe the changes in action potential shape (generally with increase of drug concentration, spike amplitude decreases and also number of spikes).




Fig 4: Screenshot of “Drugs” tab shown under “Variables” section. Slider bar is shown with pointed arrows. Check pronase activation button to prevent sodium inactivation.



Fig 5: Screenshot of the neuron simulator showing simulation controls. Click “Run” first (green arrow) and then “Stim1”/”Stim2” (red arrow) according to your input pattern. 


Sample Simulation Results:


Figures 6-8 shows some preliminary simulations run for the user to understand how the drugs/blockers effect the action potential generation. Each figure legend gives an in detail explanation of what the figures represent.  




 Fig 6: Action potential recordings from neuron simulator under different conditions. Left figure  shows recording at control condition (where no blockers were used). Right figure shows recorded action potential when 50% TTX applied (no TEA and pronase). Bottom figure shows recorded action potential when 100% TTX applied under same condition as in B. 




Fig 7: Left figure shows action potential recorded when 50% TTX used (no TEA) and activated pronase as an antagonist to TTX. Right figure shows action potential recorded when 100% TTX used with activated pronase (which is similar to Fig 6 Bottom figure). 





Fig 8: Left figure is similar to Fig 6A. Right figure shows recorded action potentials when 50% TTX and 50% TEA are used (pronase not activated). Bottom figure shows simulated result when 100% TTX and 100% TEA are used. 






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