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Modulation of hypothalamic-pituitary-interrenal axis function by social status in rainbow trout
Jennifer D Jeffrey1, Andrew J Esbaugh, Mathilakath M Vijayan
1Department of Biology, University of Ottawa, Ottawa, Ontario, Canada.
General and Comparative Endocrinology
|February 14, 2012
Summary
Social status in rainbow trout affects the hypothalamic-pituitary-interrenal (HPI) axis. Subordinate fish show altered cortisol dynamics and reduced response, while dominant fish exhibit enhanced steroid biosynthesis for stress adaptation.
Area of Science:
- Endocrinology
- Neuroendocrinology
- Animal Behavior
Background:
- Social hierarchies are common in fish, driven by resource competition.
- Subordinate individuals often exhibit chronic stress responses, indicated by elevated cortisol.
- The hypothalamic-pituitary-interrenal (HPI) axis regulates stress response in vertebrates.
Purpose of the Study:
- To investigate how social status influences the expression of HPI axis proteins in juvenile rainbow trout.
- To determine if cortisol treatment and fasting mimic stress responses seen in subordinate fish.
Main Methods:
- Establishing dominance hierarchies in paired juvenile rainbow trout.
- Measuring plasma adrenocorticotropic hormone (ACTH) and cortisol levels.
- Analyzing mRNA expression of key HPI axis genes (CRF, CRF-BP, MC2R, StAR, P450scc) and glucocorticoid receptor (GR) protein levels.
Main Results:
- Social status modulated ACTH levels, cortisol synthesis, and liver GR expression.
- Subordinate trout had lower ACTH and liver GR levels, suggesting altered cortisol feedback and target tissue response.
- Dominant trout showed elevated mRNA levels for steroidogenic acute regulatory protein (StAR) and cytochrome P450 side chain cleavage (P450scc), indicating enhanced steroid biosynthesis.
Conclusions:
- Social status significantly impacts HPI axis function in rainbow trout.
- Subordinate fish display characteristics of chronic stress with reduced cortisol response.
- Dominant fish may possess an adaptive advantage due to enhanced steroidogenic capacity for future stressors.
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