Abstract
Environmental enrichment (EE) reduces drug and sucrose cue-reactivity in rats. In a previous study we reported that 1 month of EE (large cage, toys, and social cohorts) significantly reduced sucrose cue-reactivity. In the present study, we examined whether overnight (22 h) EE would be as effective. We also examined whether social enrichment (SE), enrichment alone (SoloEE), or exposure to an alternative environment (AEnv) might account for the EE effect. Rats self-administered 10% sucrose (.2 mL/delivery) in 10 daily 2-h sessions. Sucrose delivery was accompanied by a tone+light cue. Rats were then exposed to enrichment or alternative environment conditions overnight (acute) or for 29 days (chronic). Sucrose cue-reactivity was measured after this period of forced abstinence in a session identical to training, but no sucrose was delivered with the cue. All acute conditions markedly reduced sucrose cue-reactivity after 1 day of forced abstinence compared to single-housed rats in standard vivarium housing (CON). Sucrose consumption was also significantly reduced in all groups but SoloEE in a next-day test. All acute conditions but SE significantly reduced sucrose cue-reactivity when administered just prior to Day 30 of forced abstinence; all reduced sucrose consumption in a next-day test. All chronic conditions except for SE and AEnv significantly reduced sucrose cue-reactivity on the Day 30 test and sucrose consumption in a next day test. For both acute and chronic comparisons, EE manipulations were the most effective at reducing sucrose cue-reactivity and consumption. SoloEE and EE were equally effective at reducing sucrose cue-reactivity and similarly effective at reducing sucrose consumption. This indicates that social interaction is not a necessary condition for reducing sucrose-motivated behaviors. These results may be useful in the development of anti-relapse strategies for drug and food addictions.
Highlights
Drug abuse continues to contribute to negative health and social outcomes [1,2]
Rats acquire self-administration in daily sessions in operant conditioning chambers where lever responding is reinforced with liquid sucrose deliveries that are paired with the presentation of a visual and auditory stimulus
It did appear that the nonsignificant social enrichment (SE) manipulations (SE Acute Day 30 and SE Chronic) had some efficacy, those effects may have been masked by our statistical approach
Summary
Drug abuse continues to contribute to negative health and social outcomes [1,2]. Attention has recently turned to excessive food consumption (‘‘food abuse’’) as obesity rates have doubled in some regions of the US between 1999–2008 [3]. Sucrose self-administration by rats provides a model of addiction behaviors relevant to understanding drug addiction, but even food preoccupation behaviors that may contribute to overeating and obesity [7]. Rats will respond for delivery of this stimulus, and this response rate increases over a period of forced abstinence from sucrose selfadministration [8]. This abstinence-dependent increase in sucrose cue-reactivity (‘‘incubation of craving’’) is similar to what has been observed in rats with a history of drug (cocaine, methamphetamine, nicotine, alcohol) self-administration and in humans with a history of cocaine, heroin, or cigarette abuse [7]
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