Notes for Session 5a (2/9 and 2/11/99)

More and Better Action Potentials

You can begin by reviewing your notes and the writeup for last week.

Today's oocytes have been co-injected with better-tuned quantities of three different channels:
electrically excitable Na
tansient K ("shaker").
sustained K (Kv1.3).

(You can place an oocyte under voltage clamp and try a traditional depolarizing step to verify the presence of all these currents; but the main experiments will be under current clamp).

These oocytes may fire reptitive trains of impulses.  Don't forget to keep cells at -80 to -90 mV to remove resting inctivation.  Give depolarizing current of various amplitudes and study firing frequencies as a function of current.

You may it convenient to use the chart recorder to record the impulse trains.  You won't resolve the spike waveforms; but since these are all-or-none, you don't care.  You might even use the manual controls on the Gene clamp to control the current flow.  As usual, fell free to experiment and modify the instrumentation.

Are you ready to use a Hodgkin-Huxley simulator to predict your firing freqencies on the basis of the voltage-clamp data?  Simulations of this sort **alone** are not a suitable indpendent project!  Contact Henry for a package called "Axon Engineer" that might do a good job; or adapt the Bower lab's program, Genesis, for this purpose (you'll need UNIX or Linux--not on the Lab machines).  Another program, Neuron, does work under Windows.  You get get it here and try it.