[Neuroscience] Aspiration of buffer during electrophysiology

Trevor Lewis via neur-sci%40net.bio.net (by t.lewis from unsw.edu.au)
Sun Aug 5 17:53:38 EST 2007


Dear Bill,

I have a couple of tricks that I use to reduce both the electrical 
noise and the changes in bath solution level. Rather than use a very 
high suction rate to break-up the solution into beads, I place a 
bubble trap close to the microscope stage, with a short length of 
tubing going to suck solution off from the bath. The bubble trap is 
nothing special - a cut-down 5 ml syringe with a rubber stopper in 
the open end and a hypodermic needle going through the stopper. That 
way there is a luer fitting on each end to connect the tubing. The 
important aspects are 1) to keep the line from the bath to the bubble 
trap short, and 2) to keep the bubble trap close to the grounded 
(shielded) environment of the stage. I usually find that placing the 
bubble trap just below the level of the stage and towards the rear is 
a good position. We've used several methods of attaching the bubble 
trap, including velcro (the velcro with adhesive on one side) and 
sometimes there is a convenient structure to strap the bubble trap to 
with cable ties.
The second trick is having a sloping surface at some location that 
enters the bath and then locating your suction pipe so that it sits 
flush (parallel) to this sloping surface and just comes into contact 
with the solution. This setup uses surface tension to your advantage 
rather than trying to work against it. I haven't played around a lot 
with the angle of the sloping surface; I use around 40 deg above the 
horizontal.
With both these tricks I find that I can get away with a much less 
powerful suction and still get efficient solution exchange.

This works for me, but like a lot of things in electrophysiology, 
there is always more than one way that works.
Good luck.

Trevor Lewis




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