Dominant mice show much lower concentrations of methionine-enkephalin in brain tissue than subordinates: cause or effect?
Possible relationships between dominance rank and brain methionine-enkephalin content were studied by using a method of consecutive rank determination in groups of mice reassembled according to their initial ordinal dominance rank. Thus, 10 groups of 3 Balb/c AnN mice of identical ordinal rank were formed with the consecutive dominants of 3 groups of 10 mice. Dominant, subdominant, subordinate and non-aggressive mice were recognized in these groups. Rank order was strongly correlated with brain Met-enkephalin content. Dominant mice contain less than a fourth Met-enkephalin immunologic reactivity in the brainstem and about half the forebrain concentration than subordinates. Brainstem Met-enkephalin correlated with the final ordinal rank and, accordingly, it was found to decrease exponentially after mice acquired alpha-dominance status. Different concentrations in the forebrain correlated with the initial but not the final ordinal rank and, therefore, probably preceded dominance status.
Díaz
J L
JL
Departamento de Fisiología, Universidad Nacional Autónoma de México, Mexico City.
Asai
M
M
D000374:Aggression / Q000502:physiology; D000378:Agonistic Behavior / Q000502:physiology*; D000818:Animals; D001143:Arousal / Q000502:physiology*; D001921:Brain / Q000502:physiology*; D001933:Brain Stem / Q000502:physiology; D002540:Cerebral Cortex / Q000502:physiology; D004291:Dominance-Subordination; D004744:Enkephalin, Methionine / Q000502:physiology*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D011863:Radioimmunoassay
D004744:Enkephalin, Methionine