Environmental conditions can dramatically influence the behavioral and neurochemical effects of drugs of abuse. For example, stress increases the reinforcing effects of drugs and plays an important role in determining the vulnerability to develop drug addiction. On the other hand, positive conditions, such as environmental enrichment, can reduce the reinforcing effects of psychostimulants and may provide protection against the development of drug addiction. However, whether environmental enrichment can be used to “treat” drug addiction has not been investigated. In this study, we first exposed mice to drugs and induced addiction-related behaviors and only afterward exposed them to enriched environments. We found that 30 days of environmental enrichment completely eliminates behavioral sensitization and conditioned place preference to cocaine. In addition, housing mice in enriched environments after the development of conditioned place preference prevents cocaine-induced reinstatement of conditioned place preference and reduces activation of the brain circuitry involved in cocaine-induced reinstatement. Altogether, these results demonstrate that environmental enrichment can eliminate already established addiction-related behaviors in mice and suggest that environmental stimulation may be a fundamental factor in facilitating abstinence and preventing relapse to cocaine addiction.
Wednesday, November 12, 2008
Undoing cocaine's consequences.
In animal experiments stressful and aversive conditions can enhance drug-seeking and drug intake, while stress-reducing manipulations and nondrug rewards can reduce such behaviors. The acquisition of addiction-related behaviors such as sensitization and drug self-administration is attenuated in animals housed in enriched environments containing novel toys, food, and conspecifics with which to interact, compared with those housed in standard laboratory conditions. But, how is this relevant to treating drug-addicted humans, who present for treatment only after drug use is acquired? Recent work by Solinas et al. now suggests that environmental enrichment can still exert its beneficial effects on addiction-related behaviors even after they are established. Their abstract: