Effect of the environmental enrichment on the severity of psychological dependence and voluntary methamphetamine consumption in methamphetamine withdrawn rats

Previously results have been shown that chronic methamphetamine causes dependence, withdrawal syndrome and drug craving. Also, environmental enrichment (EE) has been shown protective effects in several animal models of addiction. This study evaluated effect of the EE on the anxiety-depression profile and voluntary METH consumption in METH-dependent rats after abstinence. The rats were chronically treated with bi-daily doses (2 mg/kg, at 12 h intervals) of METH over a period of 14 days. METH dependent rats reared in standard environment (SE) or EE during spontaneous METH withdrawal which lasted 30 days. Then, the rats were tested for anxiety (the elevated plus maze-EPM) and depression (forced swim test-FST) and also voluntary consumption of METH using a two-bottle choice paradigm (TBC). The results showed that the EE rats exhibited an increase in EPM open arm time and entries (P < 0.05), lower levels of immobility (P < 0.001) as compared with the SE groups. Preference ratio of METH was less in the METH/EE rats than the SE group during 2 periods of the intake of drug (P < 0.05). Environmental enrichment seems to be one of the strategies in reduction of behavioral deficits and the risk of relapse induced by METH withdrawal.