OBJECTIVETo study the effects of early enriched environment on behavioral development and serum corticosterone level in rats.

METHODSForty-five neonatal rats were randomly assigned into three groups：blank control, enriched environment and isolated environment. The open-field environment test and the Lat maze test were performed to assess anxiety/irritability-related behaviors of the rats on postnatal day 31. The level of serum corticosterone was measured by radioimmunology assay.

RESULTSThe level of serum corticosterone in the enriched environment group (8±3 ng/mL) was significantly lower than the blank control (11±4 ng/mL) and the isolated groups (22±4 ng/mL) (P<0.01). The open-field environment test showed that the numbers of passing panels, keeping an erect posture and grooming were less than those in the blank control and the isolated groups (P<0.05). According to the results of the Lat maze test, the frequencies of running across the corner, keeping an erect posture and leaning against the wall in the enriched environment group were less than those in the blank control and the isolated groups (P<0.05).

CONCLUSIONSEarly enriched environment can decrease serum corticosterone level and thus alleviates anxiety and irritability in rats. It may play an important role in the improvement of brain development.