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The active phase-related increase in corticosterone and aggression are linked
J Haller1, S Millar, J van de Schraaf
1Institute of Experimental Medicine, Hungarian Academy of Science, Budapest, Hungary.; Leiden/Amsterdam Center for Drug Research, Sylvius Laboratories, Leiden, The Netherlands.
Journal of Neuroendocrinology
|May 3, 2000
Summary
Corticosterone levels naturally rise at dusk, coinciding with increased aggression in male rats. Blocking the mineralocorticoid receptor with spironolactone significantly reduced this territorial aggression.
Area of Science:
- Neuroendocrinology
- Animal Behavior
Background:
- Corticosterone influences behavior, with peak production at the onset of the dark period.
- Male rats exhibit heightened aggression during the dark phase.
Purpose of the Study:
- To establish a causal link between the rise in corticosterone at the dark period onset and increased male rat aggression.
- To investigate the role of mineralocorticoid receptors (MR) in mediating this aggressive behavior.
Main Methods:
- Quantified plasma corticosterone levels and aggressive behavior in territorial male rats across the day-night transition.
- Administered spironolactone (a MR blocker) at specific doses (5 or 10 mg/kg) during the early dark period.
Main Results:
- Low corticosterone and aggression were observed during the light period.
- A surge in plasma corticosterone preceded the dark phase, correlating with peak aggressive responding.
- Aggression remained elevated in the early dark period when corticosterone levels were high.
- Spironolactone treatment significantly reduced territorial aggression, indicating MR involvement.
Conclusions:
- The increase in corticosterone at the onset of the dark period is causally linked to heightened territorial aggression in male rats.
- The high-affinity mineralocorticoid receptor plays a specific role in mediating this light-cycle-dependent aggressive behavior.