CO2 to sedate animals - (May/22/2013 )

Interesting discussion. In our lab the mice to be killed are put into a CO2 chamber. Then they get convulsions and you can observe a really heavy breathing. They are then taken out and killed by breaking the neck. I always wondered at which point they are dead ? At the moment of breaking the neck or already before ? Can someone tell me ?

For sedation they get something injected, but I don't know what.

Sedation of mice is usually done with ketamine. CO2 is not a good option as it has a very high risk of death if you get the dose wrong, and when you switch it off, the mice will revive very quickly if they aren't dead.

@Tabaluga, the CO2 should kill them if they are left there for long enough. THe trick with CO2 is to increase the level slowly so that the mice go to sleep before dying. If you increase too quickly, the mice will convulse, bleed from the nose and pant really heavily. Breathing in high concentrations of CO2 is very painful too (If you want to try this for yourself get someone to watch you first of all, then put some dry ice into a sink or bucket, leave for a while and then olwer your nose just below the lip of the bucket and inhale).

We did a short study at Life in copenhagen, to determine the stress induced by CO2 sedation and ketamine sedation, by measuring cortisol buildups over an extended time. No significant difference where detected the two groups inbetween, but compared to the controls, both had elevated cortisol levels. (based on ELISA). Regardless of the method, forcing a mammals body to act against it's natural state, will stress the animal. A downside with using CO2 is, as more have already stated, that done by unskilled personel, deaths may occure due to overexposure or shock.