Pain associated behaviour
Rats seldom vomit. They are able to passively cast up or regurgitate food. When a rat is 'nauseated', it may repeatedly lift its head in a motion resembling gagging. They can also display pica-behaviour, which is defined as eating bedding material or other strange, non-food objects.
When rats experience pain, they communicate by squeaking, whistling and screeching, and by producing ultrasound.