NaCl-agar bridge

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Morgado's picture
NaCl-agar bridge

Hi all,

I have read in a paper (PMID: 17056667) : “the pipette was coated with sticky wax close to the tip to reduce capacitance”. What is this wax and what is it for exactly? How do we apply it to the patch pipette? Where can we get it?

In the same paper: “a 1M NaCl-agar bridge between the bath and the Ag-AgCl reference electrode was used to minimize offset potentials (<2 mV)”. Where can we get this bridge? How do we install this bridge? Can anyone send me a photo showing that bridge installed?

Thanks in advance

Arvind Singh Pundir
Arvind Singh Pundir's picture
 answere to your first part

 answere to your first part is
sticky wax is applied to Pipette tips  to reduce stray capacitance
Sticky wax can be purchased from many suppliers of dental products  on of them is
Kerr, Emeryville, CA, go te the link and find out 

Fraser Moss
Fraser Moss's picture
another vendor is http://www

another vendor is that sell "model cement"
the Kerr product you want is "Kerr sticky wax 00623"
Agar bridges are something you make yourself with some agar, a capilliary tube and 3M KCL.
See this book for a description of how to build and use one
Patch clamping: an introductory guide to patch clamp electrophysiology
By Areles Molleman
Edition: illustrated, reprint
Published by John Wiley and Sons, 2003
ISBN 047148685X, 9780471486855
you can read the relevant section online (pages 67-70) by clicking the link below
Click Here to read book section

didani's picture
Could this kind of bridge

Could this kind of bridge minimize BIG offset problems too?
I record in CA1 in vivo and cannot zero my offset. It's stuck at -200 mV or more.

The FFM's picture
 do you have that same

 do you have that same problem when you plug in the model cell or just when you are using pipettes?

didani's picture
There is no problem with the

There is no problem with the model cell and there is also no problem when we use the same setup for in vitro recordings. It's just in vivo.  I tried 3 different grounds (i.e. 3 different wires), tried puting the grounds in cerebellum, muscle and sub-cut, and all give the same result. I've broken the glass tip so that I have less chance of clogging (I don't have the capability to apply positive pressure). Thoughts? Do you know people that record in vivo with a glass pipette?

The FFM's picture
My only experience of such a

My only experience of such a phenomenon was watching a former colleague not be able to zero is offset in vitro.

The problem turned out to be some salt/chemical from a previous experiment had dried in the recording chamber and was re-dissolving into his perfused solutions and causing the de-chlorination of his reference electrode.

Maybe contact Anthony Dickenson at University College London who performs in vivo recordings on spinal cord preps -