Stirring Up New Ideas About the Regulation of the Hypothalamic-Pituitary-Interrenal Axis in Zebrafish (Danio rerio)

Abstract

The dynamic relationships between the changes in cortisol synthesis during and after a stressor and the expression pattern of the key genes that regulate the different levels of the hypothalamic-pituitary-interrenal (HPI) stress axis are poorly understood. This study established a novel vortex stressor and characterized its impact at all levels of the HPI axis in adult zebrafish. Exposure to a moderate vortex speed for 60 min was associated with a marked 18-fold increase in whole-body cortisol after 10 min followed by a gradual return to basal values 30 min poststress. The changes in whole-body cortisol were paralleled by increases in the expression of preoptic area corticotropin-releasing factor, pituitary prohormone convertase 1, and interrenal melanocortin 2 receptor, steroid acute regulatory protein, 11β-hydroxylase and 11β-hydroxysteroid dehydrogenase 2. The response to the vortex stressor also included delayed increases in preoptic area urotensin I and pituitary pro-opiomelanocortin mRNA levels but no change in the expression of other putative HPI axis regulators. Notably, the expression of several genes was depressed below control values 30 min poststress. These findings suggest that multiple genes at all levels of the HPI axis play an active role in the stimulation and termination of the cortisol stress response in zebrafish.

Programming of the hypothalamic-pituitary-interrenal axis by maternal social status in zebrafish (Danio rerio)

“…Cortisol was extracted from a subset (N=12 per treatment group) of adult female zebrafish using a protocol adapted from Fuzzen et al (2010Fuzzen et al ( , 2011. In brief, zebrafish were powdered in liquid nitrogen with a mortar and pestle prior to homogenization with a handheld homogenizer (PowerGen 125, Fisher Scientific, Ottawa, ON, Canada) on ice in 400 μl of homogenization buffer (80 mmol l −1 Na 2 HPO 4 , 20 mmol l −1 NaH 2 PO 4 , 100 mmol l −1 NaCl, 1 mmol l…”

11β-Hydroxysteroid dehydrogenase type 2 in zebrafish brain: a functional role in hypothalamus-pituitary-interrenal axis regulation

“…Stressor exposure Experiment 1 To establish the in vivo regulation of brain Hsd11b2 expression and activity in response to stress, adult mixed-sex fish were subjected to a 1-min air exposure and allowed to recover for 20 min (nZ6), 1 h (nZ16), 4 h (nZ16), and 24 h (nZ16) poststressor exposure as described previously (Fuzzen et al 2010). At the end of the recovery period, fish were terminally anesthetized as earlier.…”

“…Gene-specific primer sequences are as reported in Alsop & Vijayan (2008). Transcript abundance was calculated by fitting the threshold cycle to the antilog of a standard curve made from serially diluted cDNA, and all samples were normalized to the abundance of elongation factor 1a (ef1a; primer sequences reported in Fuzzen et al (2010)); the threshold cycle for ef1a was similar in all samples and hence used for normalization. All non-RT controls failed to amplify confirming the absence of genomic contamination, while single-peaked dissociation curves confirmed specific amplification of a single product.…”

“…suggesting transcriptional regulation (Nematollahi et al 2009, Fuzzen et al 2010. However, more studies are needed to tease out the direction, timing, and tissue specificity of hsd11b2 regulation by cortisol.…”

A comparison of two methods for the assessment of stress axis activity in wild fish in relation to wastewater effluent exposure

“…WBIC has been widely used for assessing cortisol levels during stress, in a variety of fish species (Fuzzen et al, 2010;Pottinger and Calder, 1995;Pottinger et al, 2002). However, although measurement of WBIC is very effective at discriminating between unstressed and stressed individuals (e.g.…”