I don't know what you or the OP are thinking of, but it's worth pointing out that the placebo effect is not just a phenomenon in the patients' minds; it can also be a phenomenon in doctors' minds.

In brief, any time you have a subjective measurement (for instance, the experimenter assigns a number from 1 to 5 based on how "distressed" the mice -- or human patients -- look), that subjective measurement can be subtly biased. So if the experimenter doesn't blind his experiments properly, you can see a placebo effect in animal studies.

It is appropriate to refer to these studies as double or triple blind because the single blind usually refers to the patient.

  Single blind: patients do not know which group they are in
  Double blind: experimenters do not know the group identities
  Triple blind: overseeing committees do not know the group identities

So animal studies can be assumed to be single blind by default, and become double-blind when the experimenters do not know the group identities.