The effects of prenatal stress on learning in rats in a Morris maze.

The offspring of female Wistar rats subjected to daily stress (they were placed in an unfamiliar social group for 1 h) during the last third of pregnancy were studied. The offspring of these females were tested for the ability to perform spatial orientation in a Morris water maze at the ages of two and four months. Prenatal stress had no effect on the ability of rats to learn in the Morris maze. However, two-month-old animals subjected to prenatal stress, unlike controls, demonstrated less flexibility in their behavioral strategy in solving the spatial orientation task. These animals were characterized by a clear tendency for their behavior to perseverate. By the age of four months, the differences between the control and prenatally stressed animals had disappeared.