Note
A growing literature attests to the fact that the environment in which a drug is given can have a profound effect on the development and expression of tolerance and sensitization. The dominant paradigm for studying such context-dependency is based on Pavlovian conditioning, in which a distinctive environment serves as a conditioned stimulus. Context dependency is demonstrated when tolerance or sensitization is expressed only in the environment in which the drug was given chronically. An alternative paradigm for studying context-dependency is to manipulate the contingencies of reinforcement operating in the environment in which the drug is administered.