Environmental enrichment induces early heroin abstinence in an animal conflict model

Heroin addiction is a significant health and societal problem for which there is no highly effective long-term behavioral or pharmacological treatment. Therefore, strategies that support heroin abstinence should be a primary focus of heroin treatment research. To this end, the current study used an animal conflict model that captures the aversive consequences of drug seeking (as are typical in humans, e.g., incarceration and job loss) to induce abstinence. Using this abstinence model, we examined the capacity of environmental enrichment (EE) to facilitate abstinence in heroin seeking rats.

The procedure consisted of two phases: drug self-administration (phase 1) and electric barrier application (phase 2) that resulted in abstinence. For phase 1, male rats were trained to self-administer intravenous heroin under a fixed-ratio schedule of reinforcement. After self-administration was acquired, animals were housed either in EE or standard cages (non-EE control). During abstinence in phase 2, the electric barrier was introduced in the operant conditioning chambers by electrifying the floor area near the levers.

We found that EE rats achieved abstinence (zero active lever presses for 3 consecutive sessions) in significantly fewer sessions than NEE rats. Further, EE rats abstained at significantly lower electric currents than NEE rats.

EE facilitated abstinence in the conflict model. The current use of the abstinence-conflict model to investigate EE as a behavioral strategy to facilitate abstinence will help in the development of effective treatments for human addicts by bringing together the positive consequences of abstinent behavior in an enriched environment with the aversive consequences of drug seeking.