Ketamine/Xylazine dose for rats?

[rgazzara at fdant.nctr.fda.gov]

In article <3pdsro$388 at news.cuny.edu> Vagell at MSVAX.MSSM.EDU (Michael Vagell) writes:
>Subject: Ketamine/Xylazine dose for rats?
>From: Vagell at MSVAX.MSSM.EDU (Michael Vagell)
>Date: 17 May 1995 22:20:40 GMT

>What doses of Ketamine & Xylaxine (Rompum) should be administered for
>30-45min deep anesthesia during stereotaxic surgery in adult male Long
>Evans rats (300-400g)?  I have been using 100mg/Kg Ketamine ip and
>15mg/Kg Xylaxine im with good results up until now.  It is the
>strangest thing.  We seem to lose  a lot of animals after 5pm (the
>animals are kept on a 12:12 reverse light/dark schedule).  Does anyone
>else find this temporal hypersensitivity in rodent anesthesia?  Any
>suggestions for different doses or using another anesthetic agent? 

>Vagell at msvax.mssm.edu
>Michael Vagell
>Department of Cell Biology and Anatomy
>Mount Sinai School of Medicine
>New York, N.Y.

We are planning to use a ketamine/xylazine combination to produce short-term 
anesthesia in newborn rat pups (SD) in order to inject a tract-tracer into the 
tongue.  We were planning to use a dose suggested in a paper by Van Pelt 
(JAVMA, Vol. 171, pgs. 842-844, 1977) in which he gave varying amounts of 
ketamine and/or xylazine i.m.  He seemed to favor 87 mg/kg ketamine in 
combination with 13 mg/kg xylazine, simultaneously, i.m.

Does anyone have any experience with ketamine/xylazine in neonatal rats?  We 
would appreciate any comments on suitable doses.  We are planning to 
administer the anesthetic s.c.

Thanks for any advice or suggestions you can give.

Russ Gazzara
Division of Reproductive & Developmental Toxicology
National Center for Toxicological Research
Jefferson, AR