Short communication Naltrexone attenuates cue- but not drug-induced methamphetamine seeking: a possible mechanism for the dissociation of primary and secondary reward

AbstractThe present study was aimed to clarify the role of the opioid system in the reinstatement of methamphetamine (METH)-seeking behaviorin METH self-administering rats. Following 12 days of self-administration of METH, the replacement of METH with saline resulted in agradual decrease in lever press responses (extinction). Under extinction conditions, METH-priming or re-exposure to cues previously pairedwith METH infusion markedly increased the responses (reinstatement of drug-seeking). Naltrexone administered 30 min before re-exposureto METH-associated cues attenuated reinstatement of drug-seeking behavior. On the other hand, administration of this antagonist had noeffect on the reinstatement induced by METH-priming. We discussed these findings in relation with the dissociation of primary andsecondary reward, suggesting that an opioid mechanism is responsible for this dissociation. Further, these results indicate the possibility ofusing naltrexone as an anti-relapse agent.D 2004 Elsevier B.V. All rights reserved.