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rat anesthesia

Leslie Kay lmk2 at garnet.berkeley.edu
Fri Dec 9 18:17:05 EST 1994

In article <3cagth$p5o at gazette.bcm.tmc.edu>,
Sarah Pallas <pallas at cephalo.neusc.bcm.tmc.edu> wrote:
>I'm curious how other people anesthetize their rats.  I don't like to
>use barbiturates because of the danger of overdose, but other methods
>seem not to last long enough for a surgical procedure that takes over
>15 minutes.  I usually work in larger animals but I'm thinking about
>doing more with rats for economic reasons.

I do a procedure that lasts 2-6 hours, so perhaps my methods are a bit
much for a 15-20 minute procedure.  I use "rat cocktail": ketamine, xylazine,
and ACE to begin.  This puts them under for a couple of hours, but the problem
is that it's unclear what portion of that time they are really
anesthetized instead of just motionless.  In addition, if you're
doing electrophysiology ketamine produces beautiful but pathological
oscillations, and the effects take a day or two to wear off.  Since I'm
doing chronic implants I don't have to worry so much about that.  
After using the rat cocktail to put them under I use an IV catheter
(tail vein) to deliver Nembutal.  I haven't had any problems with 
overdosing (knock on wood), and for a 400-500 g male rat I use an
initial dose of 0.2ml (50 mg/ml).  That with the ketamine mix keeps
them under for 1.5 to 2.5 hours.  Then I supplement with 0.1 ml
everytime they show any reflex or breathing increases.  I know a guy
who just gives them an initial IP dose of 0.3-0.5 ml and the rat is under
for 2-3 hours (no ketamine).  IP administration is an easier way to go for a 
shorter procedure.  Some people use just the rat cocktail (as above), 
but the problems with determining anesthesia make me shy away from this.
Of course all the dosages need to be adjusted for weight.

Hope this helps,
Leslie Kay
lmk2 at garnet.berkeley.edu

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