Brain cortisol receptor expression differs in Arctic charr displaying opposite coping styles.

Area of Science:

• Neuroendocrinology
• Animal Behavior
• Physiology

Background:

• Consistent individual differences in behavioral and physiological stress responses, known as coping styles, are observed across species.
• The hypothalamic-pituitary axis, particularly glucocorticoid (GR) and mineralocorticoid (MR) receptors, is implicated in regulating these coping styles.

Purpose of the Study:

• To investigate the neuroendocrine differences between proactive and reactive coping styles in fish.
• To determine the role of GR and MR in mediating stress responses and coping mechanisms.

Main Methods:

• Fish were categorized into proactive and reactive coping styles using principal component analysis of behavioral data from stress tests.
• Plasma cortisol, serotonin neurochemistry, and hypothalamic mRNA expression of GR1 and MR were analyzed in relation to coping style.

Main Results:

• Proactive fish displayed lower serotonergic activity and higher activity levels under stress compared to reactive fish.
• Hypothalamic GR1 and MR abundance, along with the MR/GR1 ratio, were significantly higher in proactive fish.
• No significant differences were found in plasma cortisol or telencephalic GR1 and MR mRNA expression.

Conclusions:

• Higher brain MR and GR expression in proactive fish suggests enhanced tolerance and performance under stress.
• Evidence points to a conserved neuroendocrine mechanism associated with coping styles in a diverse fish species.
• This model may be valuable for studying climate change effects on fish populations.