We investigated heart rate (HR), temperature (T), and physical activity (Act) (by means of radiotelemetry) in male mice subjected to chronic psychosocial stress. Resident/intruder dyads lived in sensory contact for 15 days with the possibility to physically interact daily during the light phase for a maximum of 15 min. Intruders becoming dominants (InD) or subordinates (InS) were investigated here. The aims were to investigate; if a daily aggressive interaction would result in adaptation of autonomic responses; the effects of the social stress on daily rhythmicity and the way these effects change over time; whether acute and long-term autonomic changes do correlate; to compare dominants and subordinates. InD and InS showed a strong autonomic activation during the interactions, with moderate (InS) or no (InD) habituation over time. On the long term, InD showed tachycardia and marked hyperthermia but normal physical activity, while InS showed tachycardia, slight hyperthermia, and depressed physical activity. No correlation emerged between the acute and the long-term autonomic responses. These results highlight the existence of a sustained autonomic activation under chronic stress, which was also affected by mice social status.
Bibliographical noteFunding Information:
This paper was financially supported by Italian MIUR (COFIN 2000) and University of Parma (FIL 2000). We acknowledge the contribution of Maarten Kole for comments on the manuscript, as well as Valeria Vascelli and Romano Romani for technical assistance. Finally, we wish to thank two anonymous referees for their comments that substantially improved the paper.
- Acute responses
- Allostatic load
- Heart rate
- Long-term responses