Conditioned place preference: what does it add to our preclinical understanding of drug reward?

Rationale: Among the various experimental protocols that have been used to measure drug reward in laboratory animals, conditioned place preference (CP P) has been one of the most popular. However, a number of controversial iss ues have surrounded the use of this experimental protocol. Objective: The p resent review provides a theoretical overview of some critical issues relev ant to CPP. The advantages and limitations of CPP are also covered. Results : Based on modern and traditional theoretical formulations of Pavlovian con ditioning, CPP appears to reflect a preference for a context due to the con tiguous association between the context and a drug stimulus. Within this th eoretical framework, it seems clear that CPP measures a learning process th at is fundamentally distinct from drug self-administration. The main advant ages of CPP are that it: (1) tests animals in a drug-free state; (2) is sen sitive to both reward and aversion; (3) allows for simultaneous determinati on of CPP and locomotor activity; (4) is adaptable to a variety of species; (5) typically yields dose-effect curves that are monophasic rather than bi phasic; and (6) has utility in probing the neural circuits involved in drug reward. The main limitations of CPP are that it: (1) is subject to interpr etation based on the notion of novelty seeking; (2) is cumbersome for provi ding the graded dose-effect curves needed for answering some pharmacologica l questions; (3) is difficult to interpret when animals prefer one context prior to drug conditioning; and (4) lacks face validity as an experimental protocol of drug reward in humans. Conclusion: Despite some limitations, CP P provides unique information about the rewarding effect of contextual cues associated with a drug stimulus.