The stress response to sensory contact in mice: genotype effect of the stimulus animal

Male wild house mice selectively bred for long and short attack latency (LAL and SAL, respectively) were previously shown to respond differently to chronic sensory contact stress with another SAL mate. In the present study, it was investigated whether the genotype of the opponent played a role in the differential stress response of LAL and SAL mice. To this end, a LAL or SAL mate was housed either under standard conditions (i.e. with a female), single, or in sensory contact with another LAL or SAL mate for a period of 5 days. This period was chosen in order to study stress response adaptations. Although social isolation (singly housed) already induced changes in some physiological markers, in particular in LAL mice, the highest number of stress-induced changes was observed in LAL and SAL mates living opposite a mate of the other genotype. This was indicated in LAL mice by higher corticosterone levels, adrenal hypertrophy, and reduced seminal vesicle weight, and in SAL mice by higher ACTH levels and adrenal hypertrophy. Some mechanisms through which LAL and SAL mice could perceive each other as being different are proposed in the discussion, but it remains unclear why these mice show a differential stress response depending on the genotype of the opponent. In conclusion, it was demonstrated that a psychosocial stressor triggered line-specific changes in LAL and SAL mice, which were shown to be determined by the genotype of the stressor. These results open a new avenue to investigate mechanisms underlying genotypic-dependent stress responses. (c) 2005 Elsevier Ltd. All rights reserved.