Chronic buprenorphine reduces the response to sucrose-associated cues in non food-deprived rats

The mechanisms through which buprenorphine (BUP), a mixed opioid agonist-antagonist, reduces both heroin and cocaine taking remain unclear. Evidence suggests that chronic exposure to BUP blunts drug seeking by attenuating the salience of drug-associated cues. Here, we examined the effect of chronic BUP treatment (osmotic minipumps, 3.0 mg/kg/day) in rats on responding for sucrose pellets and associated cues on FR1, FR5, and PR schedules and on extinction and reinstatement of sucrose seeking by sucrose priming. The effect of chronic BUP treatment on the dopamine (DA) response in the nucleus accumbens (NAc) to sucrose pellets and to lab chow was also measured using in vivo microdialysis. Whereas chronic BUP treatment had only a modest effect on pellet intake on the FR1 schedule, it significantly reduced responding at the outset of sessions and reduced lever pressing during sucrose-associated cue presentations. No effect was observed in the FR5 or PR schedules. BUP slightly reduced responding during extinction and significantly reduced reinstatement. Chronic BUP did not alter the NAc DA response to either sucrose pellets or lab chow, although it did significantly increase basal DA. Consistent with previous studies with heroin and cocaine, chronic BUP reduced responding in the presence of reward-related cues.