I would like to model an isolated cell body (approximately spherical, no dendrites/axons) under voltage clamp conditions with fairly high channel densities. I suspect there will be conditions under which it is non-isopotential, and want to explore this. Has anyone done this?
Chris French
Neurology
The Alfred Hospital
Melbourne
Modelling spherical cell
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I think Wil Rall did a theoretical analyais on something like this ~45
years ago for a sphere or cylinder and came to the conclusion that
nonisopotentialities collapsed within (much) less than a microsecond.
But what if diameter were, say, 0.1 AU or so . . .
Back to reality.
One might imagine three worst-case situations that would give rise
to inhomogeneous membrane potential in a spherical cell. The
trivial one is a cell-attached patch. The nontrivial ones are
Elevated or inhomogeneous cytoplasmic and/or extracellular resistivity
could contribute to inhomogeneities of membrane potential. Intra- and
extracellular structures, such as membrane-bound organelles or glia,
could restrict current flow in a way that makes Vm nonuniform.
Depending on geometry, this may or may not be suitable for NEURON--
you could be forced to use a field simulator that uses space-filling
finite elements instead of NEURON's cables.
years ago for a sphere or cylinder and came to the conclusion that
nonisopotentialities collapsed within (much) less than a microsecond.
But what if diameter were, say, 0.1 AU or so . . .
Back to reality.
One might imagine three worst-case situations that would give rise
to inhomogeneous membrane potential in a spherical cell. The
trivial one is a cell-attached patch. The nontrivial ones are
- a sphere with uniform properties that is subjected to an extracellular field
a sphere with a cluster of ion channels that are localized to a small patch of membrane
Elevated or inhomogeneous cytoplasmic and/or extracellular resistivity
could contribute to inhomogeneities of membrane potential. Intra- and
extracellular structures, such as membrane-bound organelles or glia,
could restrict current flow in a way that makes Vm nonuniform.
Depending on geometry, this may or may not be suitable for NEURON--
you could be forced to use a field simulator that uses space-filling
finite elements instead of NEURON's cables.