I am using a cocktail of 1ml ketamine, 0.5 ml Xylazine and 8.5 of saline, to anesthetize Thy1 transgenic mice.
Lately the anesthesia doesn't seem to work properly, and I spend a lot of time to make the mouse fully asleep, so it takes me hours only to be able to start the surgery.
I am injecting intraperitoneal 0.12 ml for mice of 25 grams of weight and making additional shots of 0.06, after 20 minutes if it is still showing muscular reflex after pinching.
I didn't have such problem before, the drugs are not expired and the mice are from the same colony.
Any suggestion on how to solve this problem?
I am making spinal cord experiment, so I need the muscles to be relaxed but still responsive and, of course, the mouse fully asleep.
The experiment lasts for 7-8 hours. Once the mouse is anesthetized, the surgery is performed and the experiment starts, usually, everything goes smoothly, and I need to make additional 0.06 ml shots, only every hour or hour and half.
thank you
I don't know the concentration of the agents you're using, I'll assume both are 1mg/ml. Ketamine/Xylazine is one of the most reliable combinations for sedating mice, however given how painful the procedure likely is and how long it takes, they're too short acting for my liking. The simplest modification would be to add acepromazine, that should sedate the mice enough to prolong the effects and give you an overall more robust effect. You could also add an opioid, ideally something long lasting like buprenorphine or fentanyl if you intend on redosing every 20-30 minutes.
If possible inhalation anesthetics might be better given the necessity of the mice to remain under full anesthesia for 7-8 hours, but only if you have the proper equipment, I know it's pretty expensive so few laboratories use them.
I'll leave a link to a good guideline, overall I think with that combination of drugs it can be pretty difficult to maintain anesthesia for such a long time, and most likely adding acepromazine, ketamine can be a robust agent but it usually needs the addition of a neuroleptic-type sedative if it's going to be used as a general anesthetic, similar to fentanyl/fluanisone. Benzodiazepines can be an option but they tend to lack in regards to prolonged anesthesia, and barbiturates while probably the most effective agents have a narrow therapeutic window so they're likely innapropiate for such an extensive procedure.
http://nas-sites.org/ilarjournal/previous-issues/neurobiology-of-addictive-behaviors/mice-anesthesia-analgesia-and-care-part-i-anesthetic-considerations-in-preclinical-research/
Hi Paola Salmas ,
I agree with Tomás Allende that for keeping the animal anesthetized for so long, I will choose rather inhalation anesthetics if you have the proper equipment, but If you have been following the same protocol without problems before..... the drugs are in good state and the mice are from the same colony used ...
The only thing I can suggest you is that sometimes the ip anesthesic haven't quickly effect when the site or care of injection is not correct... and the animal full asleep later. I assume that you have experience in intraperitoneal injection but if every all It's correct maybe you must check the site and handling of injection.
For if it is helpful for you, I use Ketamine:xylazine:saline (2:1:7), 0.1ml/20mg mouse weight.
Best!
Thank you Angel del Marco and Tomas Allende for your answers. I will try to change drugs concentrations, since I can't use, at the moment, inhalation anesthetics.
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