Systemic or intra-amygdala injections of glucose facilitate memory consolidation for extinction of drug-induced conditioned reward.
The conditioned place preference (CPP) task has been used extensively to investigate the neurobiological bases of drug-induced reward. The initial expression of a CPP involves memory for an association between environmental stimuli and the affective state produced by a rewarding treatment. The present experiments examined the hypothesis that post-trial administration of glucose can facilitate memory consolidation processes underlying the extinction of drug-induced CPP behaviour. Adult male Long-Evans rats acquired an amphetamine CPP, and subsequently received extinction training. Immediately following extinction training, separate groups of rats received peripheral (100 mg/kg, 500 mg/kg, or 2 g/kg) or intra-amygdala (basolateral nucleus; 1.5 micro g/0.5 micro L or 10 micro g/0.5 micro L) injections of glucose or vehicle. Peripheral (100 mg/kg and 2 g/kg) and intra-amygdala (1.5 and 10 micro g) glucose injections facilitated the extinction of amphetamine CPP behaviour relative to vehicle-injected controls. Postextinction trial peripheral or intra amygdala glucose injections that were delayed 2 h had no effect. The findings indicate that: (i) extinction of approach behaviour to drug-associated cues involves the formation of new memories that undergo a time-dependent consolidation process; and (ii), systemic or intra-amygdala administration of a known memory-enhancing agent facilitates extinction of drug-induced CPP behaviour.
Schroeder
Jason P
JP
Department of Psychology, Yale University, 2 Hillhouse Ave, New Haven CT 06520, USA.
Packard
Mark G
MG
D000661:Amphetamine / Q000494:pharmacology; D000679:Amygdala / Q000502:physiology*; D000704:Analysis of Variance; D000818:Animals; D001245:Association Learning / Q000187:drug effects; D000697:Central Nervous System Stimulants / Q000494:pharmacology; D003216:Conditioning, Operant / Q000187:drug effects* / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004333:Drug Administration Routes / Q000662:veterinary; D005108:Extinction, Psychological / Q000187:drug effects*; D005947:Glucose / Q000494:pharmacology*; D008297:Male; D008568:Memory / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D020318:Rats, Long-Evans
D000697:Central Nervous System Stimulants; D000661:Amphetamine; D005947:Glucose