Measuring the Current of Voltage Gated Na+ Channels
Measuring the Current of Voltage Gated Na+ Channels in Neuron Paper
Assignment Details Principles of Pharmacology.
QUESTION: This question has four parts (A-D). You must complete all four parts.
You are measuring the current of voltage gated Na+ channels in neurons using the whole-cell patch clamp technique.
A. Draw the expected Na+ currents when you depolarize for 50 ms from a holding potential of -100 mV to various test potentials: -70 mV, -40 mV, O mV, +65 mV 0 and +100 mV (you may superimpose the traces or draw them separately and remember to pay attention to the timescale). 0
B. Draw the I-V curve for the Na+ channel current from Part A. What is the approximate threshold voltage for activation? What is the approximate reversal potential?
C. Imagine the Na+ channel was a mutant that was permeable to all cations. Draw the 1-V curve for this mutant channel. What is the approximate reversal potential?
D. You treat the neurons with a scorpion toxin that abolishes inactivation. Draw the expected Na+ current evoked by depolarization from – 100 mV to 0 mV of 50 ms duration. Draw the expected action potential waveform before and after you add the scorpion toxin. Explain briefly (one or 2 sentences) what is happening?
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