Measuring reward with the conditioned place preference paradigm: A comprehensive review of drug effects, recent progress and new issues

This review gives an overview of recent findings and developments in resear ch on brain mechanisms of reward and reinforcement from studies using the p lace preference conditioning paradigm, with emphasis on those studies that have been published within the last decade. Methodological issues of the pa radigm (such as design of the conditioning apparatus, biased vs unbiased co nditioning, state dependency effects) are discussed. Results from studies using systemic and local (intracranial) drug administr ation, natural reinforcers, and non-drug treatments and from studies examin ing the effects of lesions are presented. Papers reporting on conditioned p lace aversion (CPA) experiments are also included. A special emphasis is pu t on the issue of tolerance and sensitization to the rewarding properties o f drugs. Transmitter systems that have been investigated with respect to their invol vement in brain reward mechanisms include dopamine, opioids, acetylcholine, GABA, serotonin, glutamate, substance P, and cholecystokinin, the motivati onal significance of which has been examined either directly, by using resp ective agonist or antagonist drugs, or indirectly, by studying the effects of these drugs on the reward induced by other drugs. For a number of these transmitters, detailed studies have been conducted to delineate the receptor subtype(s) responsible for the mediation of the obs erved drug effects, particularly in the case of dopamine, the opioids, sero tonin and glutamate. Brain sites that have been implicated in the mediation of drug-induced plac e conditioning include the 'traditional' brain reward sites, ventral tegmen tal area and nucleus accumbens, but the medial prefrontal cortex? ventral p allidum, amygdala and the pedunculopontine tegmental nucleus have also been shown to play important roles in the mediation of place conditioning induc ed by drugs or natural reinforcers. Thus, although the paradigm has also been criticized because of some inhere nt methodological problems, it is clear that during the past decade place p reference conditioning has become a valuable and firmly established and ver y widely used tool in behavioural pharmacology and addiction research. (C) 1998 Elsevier Science Ltd. All rights reserved.