Amain purpose of pharmacological research is to identify new drugs and to determine their mechanism and site of action; such findings besides the therapeutical benefit will improve our knowledge of the physiopathology of the diseases. Usually, through the comparison in different experimental models it is possible to determine the therapeutical and collateral effects of a drug. Since there are a large number of experimental models it is not always convenient or efficient to search through all those models. Drug discrimination procedures (or more appropriately, stimulus control of drugs) may offer an efficient alternative to establish the similarities and differences between drugs. The use of these models has become extended, particularly within psychopharmacology, so it is convenient to understand the theoretical principles beyond the model to evaluate its deficiencies and worth. As to drug discrimination procedures, when comparing some drugs, one of them is established as discriminative stimulus; such drug, therefore, acquires the property of controlling behavior through the stimulus cue that it produces. Under the effect of this drug, the subject must learn to emit a particular behavior which is correlated with a particular reinforce. On different occasions, the same subject is trained to emit another response correlated with some other reinforce. After performance criteria, the training drug is substituted on generalization tests with a novel or test drug to determine the similarity between them in a particular set of dimensions which were varied (effect of the drug, dose, mechanism of action, etc.). It is assumed that response selection will be a direct function of the similarity between the drugs. This particular model is exemplified with serotonin partial agonists for the 5-HT1A receptor; this class of compounds were selected due to the great interest these compounds have promoted after their possible application on depression, anxiety and food regulation, among other possible effects.
