Rank positions in rats and their relations to tissue parameters

Abstract

Spontaneous behavioral categories such as attack. submission. boxing. allogrooming, mounting. and anogenital control were investigated in nine groups of three rats each. At the same time. the number of wins in the runway test and the amount of time spent occupying access-to-water space were registered in competitive tests. Antagonistic behavior jattack and induction of submission) permitted no significant relationships to be drawn as to the results of the competitive tests. The competitive parameters. too. showed no correlation among themselves. In agreement with other authors. we reject the existence of an encompassing unidimensional rank order in rats on the basis of these results. Attack wins and induction of submission showed a positive correlation to one another as well as to relative thymus and testes weights. A high antagonistic activity was also correlated with low relative adrenal weight. large number of nuclei in the adrenal cortex. and wide tubuli seminiferi in the testes. As indicated by factor analysis. a significant decrease in body weight. low heart. thymus. liver. spleen. kidney. and testes weights. and high adrenal weight with decreased number of nuclei in the adrenal cortex were typical for rats with low aggressive rank positions. The influence of endocrine organs and diminished physical vitality in these low-ranking animals was also observed following nonsocial stress.

Prenatal cocaine alters social competition of infant, adolescent, and adult rats.

“…To give but one example, acute and chronic immobilization restraint stress has been shown to increase aggressive behavior of female rats socializing with unfamiliar females (Albonetti & Farabollini, 1993). Although social competition itself has been shown to be a stressor, the predominant finding in this area has been that it is the defeated rats that display higher corticosterone levels (Chamove & Bowman, 1978; Militzer & Reinhard, 1982). Because prenatal treatment had no effect on time spent at the water source at either age in these experiments, it cannot be concluded that the reason for increased aggression in the cocaine-exposed rats was due to their experiencing greater levels of stress following social defeat.…”

Pavlovian conditioning of aggressive behavior in blue gourami fish (Trichogaster trichopterus): Winners become winners and losers stay losers.

“…Compared with winners, losers of an aggressive encounter have lower levels of testosterone (Rose, Bernstein, & Gordon, 1975) and higher levels of circulating corticoids, or stress hormones (Bronson, 1973; Hannes et al, 1984), which predispose them to yield to dominant males (e.g., Wingfield & Silverin, 1986). Indeed, losers' adrenal glands, which secrete the corticoid hormones, become enlarged (Militzer & Reinhard, 1982).…”

Pro-social preference in an automated operant two-choice reward task under different housing conditions: Exploratory studies on pro-social decision making

“…As a proxy for the influence of dominance on the willingness to share food with a partner, we used the difference in bodyweight (i.e. between the test rat and partner) as an indicator of dominance ( Boreman and Price, 1972 ; Militzer and Reinhard, 1982 ; Smith et al, 1994 ). The correlation between bodyweight difference and BR preference was computed using Pearson’s r .…”