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Defense changes in stress nonresponsive subordinate males in a visible burrow system
R J Blanchard1, E Yudko, L Dulloog
1Department of Psychology, University of Hawaii at Manoa, 2430 Campus Road, Honolulu, HI 96822-2359, USA. blanchard@hawaii.edu
Physiology & Behavior
|May 5, 2001
Summary
Subordinate male rats experiencing stress may adopt passive defense behaviors. Stress-nonresponsive rats exhibited reduced activity and delayed righting responses, suggesting a reactive coping style influenced by social hierarchy and individual differences.
Area of Science:
- Neuroscience
- Animal Behavior
- Endocrinology
Background:
- Social hierarchy and stress impact animal behavior and physiology.
- Individual differences in stress response exist within populations.
- The hypothalamic-pituitary-adrenal (HPA) axis is central to stress regulation.
Purpose of the Study:
- To investigate how social subordination and stress responsiveness influence defensive behaviors in male rats.
- To explore the interaction between social experience and individual traits in shaping stress coping styles.
- To examine the relationship between behavioral and endocrine markers of stress.
Main Methods:
- Male rats were housed in dominant, subordinate (visible burrow system), or control conditions.
- Behavioral responses to mild and intense threatening stimuli were assessed.
- Subordinate rats were categorized as stress responsive (SRS) or nonresponsive (NRS) based on plasma corticosterone levels.
- Hormonal levels (corticosterone, testosterone) and defensive behaviors were analyzed.
Main Results:
- Stress-nonresponsive (NRS) subordinates showed reduced activity and longer latencies to right themselves in response to mild threats compared to SRS subordinates and dominants.
- No behavioral differences were observed between VBS groups when facing intense threats.
- NRS rats displayed a pattern of reduced corticosterone and testosterone responses, indicative of a passive, reactive coping style.
Conclusions:
- Stressful social experiences, particularly subordination, can shift defensive strategies towards passivity and immobility.
- Individual differences in stress responsiveness interact with social experiences to shape coping styles.
- Behavioral and endocrine changes in subordinate rats suggest a biobehavioral reactive coping style, with potential links between HPA axis activity, testosterone levels, and defensive behaviors.