Measuring capacity can be somewhat tricky. Exactly what
experimental technique are you using? What do your data look like?
How are you calculating time constant? How are you calculating
capacitance?
First, seemingly small differences in electrical technique and
equipment setting can make large differences in the time course of
recorded signals. Second, stimulating through a microelectrode
can introduce significant artificats into the recorded signal. Third,
the voltage response to an injected current rectangle does not show a
simple exponential time constant but can reflect the cable properties of
the neurites. Fourth, because of the cable properties, the area of the
neurites (certainly the region within, say, one space constant) must
be considered in calculating the area of the cell. Fifth, are you sure
your cells are actually the size you say? Where did you get the
size information? These are some of the factors you must consider.
"Edmund Müller" <edmund.mueller at freenet.de> wrote in message
news:okvi5uc3fgpdlb7bt2r710dvepg3u72699 at 4ax.com...
> Hi NG,
>> in most sources I have scanned the membrane capacity per unit area
> (microfarad/square centimeter) is given with 1 myF/cm2.
>> Analyzing my data I always come to the conclusion that the soma of my rat
> hippocampal cell must have had a surface specific capacity of about 4.5
myF/cm2.
> I assume as shape of the soma an ellipsoid with half axes 4.5, 3 and 3
micro
> meters.
>> Is this possible? If not, where could be my error? Simple calculating
errors are
> for sure excluded.
>> Thnx Edmund
