rat; lab rat
Refers specifically to the animal, especially in scientific or laboratory contexts. For a wild rat or the pest, ネズミ is more common.
We are raising rats for use in experiments.
ラットはネズミの一種です。
A rat is a kind of rodent.
The drug's safety was confirmed using laboratory rats.
The researchers used rats to investigate the drug's effects.
rat race
Borrowed from English 'rat'.