PubMed2002
Drug-induced conditioned place preference (CPP) behavior requires memory for an association between environmental cues and the affective state produced by the drug treatment. The present study investigated whether memory consolidation underlying an amphetamine CPP could be modulated by post-training intra-amygdala infusion of the local anesthetic drug bupivacaine. On 4 alternating days adult male Long-Evans rats received peripheral injections of amphetamine (2.0 mg/kg) or saline vehicle prior to confinement for 30 min to one of two compartments of a place preference apparatus, followed by post-training intra-amygdala infusions of bupivacaine (0.75% solution/1.0 microl) or saline. On day 5 the rats were given a drug-free 20-min test session, and the amount of time spent in each of the pairing compartments of the apparatus was recorded. On the test day, rats receiving post-training intra-amygdala saline injections displayed an amphetamine conditioned place preference. Post-training intra-amygdala infusions of bupivacaine blocked amphetamine CPP. Intra-amygdala infusions of bupivacaine that were delayed 1 h post-training did not block amphetamine CPP, indicating a time-dependent effect of the treatment on memory storage processes. Pre-training or pre-retention test intra-amygdala infusions of bupivacaine also blocked acquisition and expression of an amphetamine CPP, respectively. The findings indicate that the mechanism(s) by which amphetamine elicits conditioned approach responses to environmental cues can be manipulated post-training, and suggest a role for the amygdala in acquisition, consolidation, and expression of amphetamine CPP behavior.