Yep. The animals are euthanized with CO2, placed in the device, and reduced to liquid in seconds. Obviously, this is not done when specific organs need to remain intact, but if you can do your measurements from homogenized whole animal, it saves a lot of time on rapid perfusion and dissection.

Specialty devices exist, but a standard high-speed desktop centrifuge can also be used, as a mouse will generally fit into a 50 mL centrifuge tube.

Generally best not to think about it too much if you like animals, but also like biochemical sciences. But if you're after a specific enzyme that would not be destroyed by rupture of the cell wall, whole-animal sacrifice by centrifuge is the cheap and easy way to get at it.