Effects of early protein malnutrition and repeated testing upon locomotor and exploratory behaviors in the elevated plus-maze.

An elevated plus-maze was used to investigate the effects of repeated testing on the locomotor and exploratory behaviors of malnourished rats. Pup malnutrition was induced during the lactation period (0 to 21 days of age) by feeding the dams a protein-deficient diet (6% protein) and the animals were allowed to recover from weaning to 70 days of age by eating a commercial lab chow diet. Control animals were suckled by dams receiving a normal protein diet (16% protein) during the lactation period and were fed a commercial lab chow diet after weaning. At 70 days, malnourished and control animals were placed on the central platform of the elevated plus-maze facing an enclosed arm and allowed to explore for 5 min. This procedure was repeated at 24-h intervals for 6 days. The repeated testing in the elevated plus-maze did not change the total number of arm entries and attempts to enter open arms, but decreased the percentage of open arm entries, time spent in open arms, and total time spent on the central platform. These data suggest an increase in anxiety with repeated testing in the elevated plus-maze. In addition, the malnourished animals showed a larger number of both rearings and attempts to enter the open arms, suggesting a high level of exploration and/or high impulsiveness of these animals as compared to control. The elevated plus-maze proved to be a useful animal model to evaluate exploratory behaviors in early protein malnourished animals.