Hi all,
I just wanted to sort of discourage the carbon monoxide (CO) idea because it has a really high affinity for the iron molecule in hemoglobin, and essentially binds irreversibly. That means the CO will remain in a red blood cell until the cell dies, and they normally have an approximately 60 day lifespan. Even if all the red blood cells ruptured during freezing, the lack of a functional circulatory system would prevent its release from within the mouse. There is also the distinct possibility that you might euthanize yourself while administering the CO to the mouse. Keep it safe,
Rick