Reconditioning of drug-related cues: a potential contributor to relapse after drug reexposure.

To investigate the process of relapse to drug seeking caused by reexposure to drugs, we studied the consequences of recurring instances of stimuli-drug associations using heroin conditioned place preference (CPP) in rats. After original conditioning and extinction, rats received either a single compartment-heroin pairing (reconditioning) or were primed with heroin and tested for reinstatement of CPP. It was found that the session of reconditioning, but not the session of reinstatement, caused the reappearance of a preference for the heroin-paired compartment on a test given 24 h later, in drug-free conditions. The effect of reconditioning was found to be dependent on heroin doses, and was not seen when heroin injections were given outside the conditioning environment. Furthermore, a single session of reconditioning elevated heroin seeking even on a test given 96 h later. Finally, heroin seeking was found to be significantly elevated on a test given 28 days after the last extinction session whether animals received 1 or 3 reconditioning sessions. These results suggest that the motivational value of cues associated with heroin is not eliminated by extinction and, importantly, that these cues can rapidly regain their ability to promote drug seeking behavior if they are re-associated with the effect of heroin.