THE CAGE DESIGN AFFECTS INTERMALE AGGRESSION IN SMALL-GROUPS OF MALE LABORATORY MICE - STRAIN-SPECIFIC CONSEQUENCES ON SOCIAL-ORGANIZATION,AND ENDOCRINE ACTIVATIONS IN 2 INBRED STRAINS (DBA 2J AND CBA/J)/
A. Haemisch et K. Gartner, THE CAGE DESIGN AFFECTS INTERMALE AGGRESSION IN SMALL-GROUPS OF MALE LABORATORY MICE - STRAIN-SPECIFIC CONSEQUENCES ON SOCIAL-ORGANIZATION,AND ENDOCRINE ACTIVATIONS IN 2 INBRED STRAINS (DBA 2J AND CBA/J)/, Journal of experimental animal science, 36(4-5), 1994, pp. 101-116
Effects of the enrichment of conventional laboratory housing cages wit
h an additional labyrinth on intermale aggression, social organization
, and activations of the pituitary-adrenocortical and sympathetic-adre
nomedullary neuroendocrine subsystems are compared between adult male
DBA/2J and CBA/J mice, differing genetically in their intermale aggres
sion. Mice of both strains were kept three per cage for six weeks eith
er in standard laboratory cages (SC) or in enriched cages (EC). Interm
ale aggression against a strange intruder and between cagemates was mo
nitored once a week within each group. Dominance relations were derive
d from the distribution of attacks within a group. Plasma corticostero
ne titers (PCT) and activities of the tyrosinehydroxylase (TH) and phe
nylethanolamine N-methyltransferase (PNMT) were determined for each mo
use at the end of the study. The main findings were: 1. Intermale aggr
ession increased in both strains in groups kept in EC. 2. In the more
aggressive DBA/2J the pattern of social organization shifted from grou
ps with a single permanent dominant mouse in SC to groups with a frequ
ently changing dominant mouse in EC. 3. In CBA interchanges of the dom
inant mouse was prevailing and did not differ between the two housing
conditions. 4. In DBA/2J mice PCT were significantly elevated in EC. 5
. In CBA/J mice activities of TH and PNMT were significantly elevated
in EC. 6. Body weight gain was significantly delayed in mice kept in E
C in both strains. Findings revealed strainspecific environmental effe
cts on both social organization and endocrine states. The PCT increase
obtained only in DBA/2J indicate that alterations of the social relat
ions between cagemates are more likely to induce states of stress than
an increase in intermale aggression alone.