Brief communicationEnvironmental enrichment reduces the propensity to relapse following punishment-imposed abstinence of alcohol seeking
Introduction
Relapse poses a significant barrier preventing the successful treatment of alcohol use disorder, and sufferers show an enduring propensity to relapse throughout their lifetime. One factor contributing to relapse is exposure to environmental cues or contexts previously associated with alcohol use. At a population level, relapse prevention strategies aimed at extinguishing cue-induced craving have been unsuccessful [1]. As an alternative, non-pharmacological interventions, such as environmental enrichment, have well-demonstrated anti-depressive effects and can attenuate relapse-like behavior in rodents [2,3].
In a laboratory setting, environmental enrichment can be described as abundant social and cognitive stimulation that result in structural brain changes [4,5]. Indeed, recent studies have demonstrated that environmental enrichment can modify drug-seeking behaviors. Environmental enrichment introduced during periods of forced abstinence reduced incubation of craving as measured by time-dependent increases in cocaine seeking behavior [6,7]. Interestingly, when environmental enrichment is removed, the benefits on drug-seeking behavior diminish [6]. With regards to alcohol, enrichment reduced reinstatement of alcohol-induced conditioned place preference in mice [8]. Additionally, Pang et al. [9] demonstrated that during a period of abstinence from alcohol use, environmental enrichment reduced abstinence-related depressive-like behaviors and altered hypothalamic-pituitary-adrenal (HPA) axis activity in mice.
Here we examined whether environmental enrichment introduced during a period of forced abstinence following alcohol self-administration could reduce relapse-like behavior. We used a variation of the ABA renewal model where abstinence is self-imposed in Context B due to negative consequences (punishment; [10,11]). We examined context-induced relapse to alcohol seeking after an acute period of abstinence (1 day). Rats were then randomly allocated to the ‘standard housing’ group or the ‘environmental enrichment’ group for 32 days. Following this, all rats were tested for alcohol seeking behavior following prolonged abstinence. We found that environmental enrichment reduced alcohol seeking in Context A.
Section snippets
Ethics statement
All procedures performed were in accordance with the Prevention of Cruelty to Animals Act (2004), under the guidelines of the National Health and Medical Research Council (NHMRC) Australian Code of Practice for the Care and Use of animals for Experimental Purposes (2013) and approved by The Florey Institute of Neuroscience and Mental Health Animal Ethics Committee.
Animals
Inbred male iP rats (~10 weeks old, n = 36) were obtained from the breeding colony at The Florey Institute of Neuroscience and
Training and punishment data
Male alcohol-preferring iP rats were exposed to 20% (v/v) alcohol in their home-cage prior to operant training in Context A where alcohol was available without consequence. This was followed by punishment-imposed suppression of alcohol-reinforced responding in Context B using contingent foot shock (Fig. 1). During the home-cage period, there was no significant difference in alcohol consumption between rats exposed to standard housing conditions versus environmental enrichment (F1, 34 = 3.495, p
Discussion
We examined the effect of environmental enrichment on context-induced relapse to alcohol seeking following punishment-imposed abstinence and found that enrichment during abstinence reduced subsequent alcohol seeking in Context A. There was no significant effect of enrichment on alcohol seeking behavior in Context B. Additionally, there was no effect of environmental enrichment on body weight.
Our finding of a reduction of alcohol seeking behavior in Context A following environmental enrichment
Acknowledgements
We would like to thank Mitchell Hill, Lauren McKeogh and Pascale Maynard for their help with behavioral experiments. We would also like to thank Nathan Marchant and Terence Pang for their thoughtful discussions.
Author contributions
EJC and AJL designed the study; EJC and SJ conducted all experiments and analyses. All authors wrote the manuscript.
Funding and disclosure
All authors report no conflict of interest.
This work was supported by a National Health and Medical Research Council Project Grant (1105741). AJL is a NHMRC Principal Fellow (1116930) and EJC is supported by the Jack Brockhoff Early Career Researcher Grant Scheme. We acknowledge the Victorian State Government Operational Infrastructure Scheme.
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