Significant divergences between the temporal structure of the behavior in Wistar and in the spontaneously more anxious DA/Han strain of rats tested in elevated plus maze.

The aim of present research is to study the temporal structure of the behavior in two strains of rats with different basal level of emotionality. To this purpose, the temporal profile of the behavior in Wistar rat and in the spontaneously more anxious DA/Han strain was analyzed in the Elevated Plus Maze. Both quantitative and multivariate t-pattern analyses were carried out. In comparison with Wistar, DA/Han subjects showed a significant reduction of the permanence in open arm and a significant increase of the time spent in the central platform of the maze. Mean frequencies of each behavioral element showed significant modifications both in open and in closed arm. Multivariate t-pattern analyses demonstrated a very different temporal profile of behavior in the two strains: Wistar rats presented 197 t-patterns of different composition, whereas DA/Han rats only 26; as to the mean number of t-patterns, Wistar presented a value of 698.90, whereas DA/Han only 92.80. Similar clear-cut differences were detected for the mean number of t-patterns in the two arms and for the time course of such t-patterns. Present study has evidenced that the temporal organization of the bahavior in Elevated Plus Maze is differently structured in two strains of rats with different basal level of emotionality.