minature inhibitor postsynaptic currents

r norman rsn_ at _comcast.net
Thu Sep 16 18:40:20 EST 2004

On Thu, 16 Sep 2004 22:53:17 GMT, BilZ0r
<BilZ0r at TAKETHISOUThotmail.com> wrote:

>r norman <rsn_ at _comcast.net> wrote in
>news:fe3jk0pqdu9ga3er6vmjq8b2gvoc8g288a at 4ax.com: 
>> On Thu, 16 Sep 2004 06:39:30 GMT, BilZ0r
>> <BilZ0r at TAKETHISOUThotmail.com> wrote:
>>>What is minature about mIPSCs? I assume just the amplitude, but there
>>>must be something about their nature that makes them different from
>>>regular evoked and/or sponatneous IPSCs.
>> mIPSCs, just like mIPSPs or mEPSPs, are presumed to be the response to
>> the spontaneous release of single vesicles at a synapse.  Regular
>> evoked responses (current or potential, excitatory or inhibitory) are,
>> as described, evoked ordinarily by an action potential arriving at the
>> presynaptic terminal and are not miniature because they ordinarily
>> result from the simultaneous release of many vesicles.
>> Mini's are spontaneous.  The original discovery by Katz was of
>> "spontaneous miniature potentials".  They are usually called minis
>> rather than sponties.
>Thank you very much, so minature potentiatals would always be of the same 
>size? So agonists at presynaptic receptors which inhibit calcium 
>channels, would effect the rate of minature potentials, but not there 
>amplitude, while the same agonist would effect the rate and amplitude of 
>spontaneous potentials?

Minis are often of a consistent size, but not always.  Depending on
just where you are recording, they can vary for several reasons:
different quantities of transmitter release or different distances
from the recording site. They do show variation, though, sometimes
with substantial variance even though there is a single peak in the
amplitude histogram. 

Agents that influence vesicle release tend to alter the frequency but
not the amplitude.  Agents that influence postsynaptic response tend
to alter the amplitude but not the frequency.  

I don't understand the last half of your last statement.  You seem to
make a distinction between miniature potentials and spontaneous
potentials when I just told you they were the same thing.

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