Effect of voluntary exercise on open-field behavior and on aggression in the spontaneously hypertensive rat (SHR)

In the present study we investigated the influence of voluntary exercise on exploratory behavior and on aggression in the spontaneously hypertensive rat (SHR). Twenty-four SHR (8 weeks old) were randomly assigned to either an exercise group or a sedentary control group. The animals in the exercise group exhibited a spontaneous wheel running activity of 5-6 km/day during 6 weeks. The characteristic hyperexploratory behavior of SHR was lowered in the exercise group (p less than .001) as compared to the control group. The runners also showed a tendency for less aggression. In the postexercise period, when the runners' wheels were locked, the exercise group had a significant rise in aggression (p less than .01) vs the controls. The exploratory behavior returned immediately to the level of the controls, but we found no further increase in any of the parameters measured. However, the runners showed a type of displaced aggression exhibited as digging and biting in the test cage. This evidence suggests that voluntary exercise lowers the hyperexploratory behavior and aggression in the SHR and that an abrupt stop in exercise gives an "abstinence" reaction.     

An ethological analysis of open-field behavior in rats and mice

In our view open-field testing entails both a predatory encounter, which occurs as a consequence of handling and placement of subjects into the testing apparatus, and sudden social separation from conspecifics. We hypothesize, therefore, that open-field behavior represents a compromise between responses aimed at minimizing detectability as a predator evasion tactic, and those which are motivated by attempts to reinstate contact with companions. Six experiments were conducted using rats and mice to test various implications of this model. Pretest shock and the presence of a human observer each retarded the appearance of social reinstatement behaviors and enhanced responses which minimize detectability in both species. Likewise, because of diminished reinstatement tendencies animals tested in pairs froze longer than those tested individually. The applicability of this model to other aspects of open-field behavior in rodents was examined, and the contrast between this view and the general emotionality hypothesis was briefly discussed.     

Mediators of aggression among young adult offspring of depressed mothers

The current article explores the connection between maternal depression and offspring aggression during the transition to adulthood, expanding the scope of prior research on this topic. Both family-level factors (including parent-child relationship quality and maternal romantic relationship quality) and youth factors (including depression history and social functioning in midadolescence) were tested as potential mediators in a longitudinal community sample of 710 youth at ages 15 and 20. The results suggest that maternal depression confers a risk for higher levels of aggressive behavior by offspring at age 20. Structural equation models suggested that the association between maternal depression and youth aggression is fully mediated by youth history of depression by midadolescence, even when accounting for the stability of aggression between ages 15 and 20. Parent-child relationship quality, youth social functioning, and maternal relationship quality were not unique mediators of this association. Limitations and implications are discussed.     

Effects of light and noise test stimuli on the open-field behavior of Wistar rats

The effects of five difFerent stimulus situations on open-field behavior were studied in male Wistar rats. The results show that each test situation is unique and yields a different behavioral pattern. This should be taken into account with applications of the open-field method.     

Differential effects of environmental enrichment on the open-field behavior of wild and domestic Norway rats.

Early postweaning experience in an enriched environment had a greater influence on the open-field behavior and body weight of wild Norway rats than of their domestic counterparts. Genetic changes accompanying the domestication process may have reduced the relative impact of postweaning experience on the development of the domestic rat's response to changes in its environment.