Memory, learning, and participation of the cholinergic system in young rats exposed to environmental enrichment

The present study demonstrates the consequences of animal exposure to an enriched environment compared to animals living in a standard environment regarding learning and space memory. Male albino Wistar rats were exposed to an enriched environment for 4 weeks after the lactation period and tested in the Morris water maze in the distal and proximal clue version and in the arena. In the former test, the animals were tested at 50 days of age with 12 daily trials on two consecutive days. At the end of each session, scopolamine at the dose of 0.6 mg/kg/ml or saline solution was injected intraperitoneally. Twenty-eight days after the first phase, a new test consisting of a single trial was held (retest). An independent group of animals receiving no drug was subjected to the arena test and to the proximal clue version of the Morris maze. In the distal clue version the results did not show differences between groups in the first phase of the experiment. After 28 days (retest), the animals reared in a standard environment and treated with scopolamine exhibited a significant increase in latency compared to the group receiving the same drug and stimulated and to the group receiving saline. The arena data demonstrated a significant increase in exploratory activity in the group of animals reared in an enriched environment. The proximal clue version of the Morris maze did not show differences between groups. The results of the present study indicate that animals exposed to environmental enrichment react less to the amnesic effects of scopolamine and show an increase in exploratory activity.