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Na pump or leakage K

Matthew Larkum larkum at optolab.unibe.ch
Thu Jun 23 03:58:49 EST 1994

In article hxie at vms2.macc.wisc.edu, hxie at VMS2.MACC.WISC.EDU ("huiwen xie") writes:
>I have a question regarding the change in resting potential of motoneuron
>during embryogenesis. What I found in my study was that the resting
>potential of motoneuron increased as motoneurons matured.(The increase in
>resting potential means resting potential is more negative.). Theoretically,
>there are at least two factors that may be responsible for this change. One
>is the increased expression of electrogenic Na-pump onto the membrane, while
>the other will be the increased leakage K current. Although I don't know
>what really happened during their maturation, I prefer the first
>possibility. I welcome your comments. It will be appreciated if you can give
>any relevant references on Na-pump and resting potential during development.
>Steven Schie
>Department of Physiology
>University of Wisconsin-Madison

That's interesting.  I'm working on prenatal rat spinal cord.  I've seen
a lot of motoneurons with Vm between -50 and -60 mV.  These experiments
are in vitro with slice cultures so there is every chance that something
is amis.  Were you doing microelctrode impalements in vivo?

I'm sorry, I can't give you any helpful info on the Na-pump since it 
wasn't a concern of my project but maybe something might come out of
a discussion.  Anyway, I'd be interested to here more about what you
found.  It strikes me that a study of membrane potential would be hard
because one would introduce a variable leak just by impaling a neuron
and the average would always be skewed in the positive direction, never
the more hyperpolarized direction.  (By the way, I find I consistently
get a slightly better Vm by patching rather than impaling a neuron).
Also, if the dendrites are slightly depolarized (or hyperpolarized)
relative to the soma due to constant synaptic activity, then the Vm at
the soma might be dependent on the dendritic structure of the neuron
which might also undergo changes during maturation (although, then
I, at least, would have expected Vm to increase not decrease).

Well, just a few thoughts.

Department of Physiology
University of Berne

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