Is it possible to effect both positive and negative reinforcement through the same action? Consider the following scenario: a rhesus monkey is being put under severe duress somehow (isolation, sense of physical threat, whathaveyou). It is desired that a behavior, like pressing a lever, is increased. Let's say administration of a CNS depressant as a reward is used to try to get this outcome. This could possibly be seen as positive reinforcement (due to euphoriant effects in themselves) and as negative reinforcement (because stress is being taken away). Is it possible to model both sides of this picture and is this done in practice?
Yes.

In fact, the modern view of positive and negative reinforcement is that they are essentially synonyms. They are different ways of looking at the same thing, like describing a glass of water based on how full or how empty it is:


  In this paper, we reconsider the issue from the perspective of 30
  years. However, we could not find new evidence in contemporary
  research and theory that allows reliable classification of an event as
  a positive rather than a negative reinforcer.


Wikipedia as well:


  Distinguishing between positive and negative can be difficult and may
  not always be necessary; focusing on what is being removed or added
  and how it is being removed or added will determine the nature of the
  reinforcement.