I’m not sure about that one. Rats used in Universities often come from one department to another, and you don’t know what they or their parents have been through. A good friend of mine is finishing a PhD in Genetics, and the rats they experiment on are often engineered with all types of ‘quirks’ to assist in testing and experiments.
While measures exist to protect against such animals getting into the general populous, I’d not flirt with chance. Accidents do happen, and I’m sure the last thing you’d want is for your snake to pay the price.
(Although, if comic books have taught me anything, it is that a slim chance might exist for Mr. Snake to develop mutations and super-powers after eating such a rat. Hmm….)
In any event, why not buy through an online frozen-feeder store and have them delivered to your door? (That's what I plan to do, since somebody I live with has allergies to furry animals, so breeding my own/keeping live ones is not an option.)
www.rodentpro.com/
www.themousefactory.com/
www.micedirect.com/
www.frozenrodent.com/
Hope that helps!