Kinetics of DNQX and bicuculline?

Matt Jones jonesmat at physiology.wisc.edu
Mon Jul 12 15:52:37 EST 2004


tehgabriel at web.de (tomte) wrote in message news:<1adcf6cc.0407060340.4589c785 at posting.google.com>...
> Hi!
> I want to do a set of patch-clamp experiments with combined blockade
> of synaptic AMPA and GABA currents. For experimental reasons I'll have
> to do all recordings within a timespace of only a few minutes (5' up
> to max 10').
> Because I have rather few experience with DNQX/bic. I find it hard to
> forecast if this plan is feasible. So here is my question:
>    How long does it take until DNQX and bicuculline respectively reach
> their full effect on synaptic transmission? And following wash-out:
> how long does it take until their effect is attenuated in such a
> degree that synaptic activity may be comparable to the control
> situation before application of blockers?
> 
> Every comment is grateful appreciated!
> Thanks,
> Thomas


Thomas,

Most of the time spent waiting for these drugs to wash in and out
comes from the time required to exchange the solutions, not from the
binding/unbinding kinetics of the drug at the receptor. For example,
if using a "fast-perfusion" system, the wash-in and wash-out times
will be of order tens of milliseconds (assuming about 10-50 uM drug).
If using bath exchange on a dish of cultured neurons, both times will
probably be of order a few tens of seconds to a few minutes.

In slices, it takes us about 5 minutes to achieve full effect of DNQX
(5-50 uM) or bicuculline (1-50 uM), and both drugs require  5-10
minutes or more of washout before control response amplitudes come
back. Our slice chamber holds about 500 ul, and we run the flow at
about 2 ml per minute.

Matt



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