strong leak vs strong Kv currents

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Abalaba
Abalaba's picture
strong leak vs strong Kv currents

Background:
I have observed a developmental reduction in Kv current in a particular set of coincidence detecting neurons. It is widely believed that these neurons also show a developmental increase in leak current. I dont want to argue about whether I have a pure H&H leak or some moderately rectifying leak and I know many of you want more details but I think this is a conceptual question.

Problem:
As these cells age, the membrane seems more difficult to access further compounded by the reduced visibility due to myelination. The two explanations for the reduction in Kv current over development is a) I did not have a gigahom seal or b) a strong K-leak current offset the outward Kv current.

Question:
I observe up to 30nA of current (at 40mV) so I imagine a large amount of K leaving, and because the amount is so large I see some of K ions remaining around the recorded neuron, locally changing the driving force for these ions. If K-2pore leak channels were present, would the K ion influx in enough quanity as to offset a substainal portion of outward Kv current?

fatchains
fatchains's picture
A better question may be

A better question may be whether or not your ampifier can keep up with the massive leak. For example, if your Rs is 10MOhm but your cells Rin is 20MOhm, then theorically you will have a lot of error in v-commands. Given that your cells coincidence detect, and such neurons usually have unusually low Rin, it may not be possible to control the voltage of the cell at voltages far from rest.

One way to assess whether K-leak is playing a role is to isolate all K+ currents, then block the VG currents with TEA, 4AP, and DTX. If leak is present, you shouldnt see a dramatic change in the IV curve below -80mV (where most Kv channels are closed).

Also, a standard way to determine whether you maintained a GOhm seal is to check RMP. How does that look for your cells?