Heads or tails? Stressor-specific expression of corticotropin-releasing factor and urotensin I in the preoptic area and caudal neurosecretory system of rainbow trout

Abstract

Corticotropin-releasing factor (CRF)-and urotensin I (UI)-expressing cells of the preoptic area (POA) and caudal neurosecretory system (CNSS) are considered key contributors to the regulation of the stress response in fish; however, the expression pattern of these neurons to environmental and social challenges have not been compared in a single study. Therefore, we characterized in rainbow trout (Oncorhynchus mykiss) the central distribution of CRF and UI expression and quantified the POA and CNSS mRNA levels of both transcripts in response to hyperammonemia, hypoxia, isolation, or subordination. The tissue distribution demonstrated that the POA and the CNSS are dominant sites of CRF and UI expression. Comparison of the plasma cortisol levels in response to the diverse treatments showed that subordination was the most severe stressor followed by hyperammonemia, isolation, and hypoxia. In the POA, with the exception of subordination that had no effect on UI expression, all stressors resulted in increase in CRF and UI mRNA levels. In the CNSS, while hyperammonemia was associated with increase in CRF and UI mRNA levels, and hypoxia induced an increase in CRF expression, isolation caused a decrease in the expression of both transcripts, and subordination had no effect. Independent of the stressor, we found strong positive correlations between CRF and UI expression in the POA and the CNSS, and no correlation in the expression of either gene between regions. Overall, the results demonstrate that the contribution of POA and CNSS CRF and UI neurons to the stress response in rainbow trout is stressor-, time-, and region-specific.

Chronic cortisol and the regulation of food intake and the endocrine growth axis in rainbow trout

“…Fork length and BW were then recorded, and several tissues were collected to quantify the mRNA levels of key appetite-and growth-regulating genes by quantitative real-time RT-PCR (qRT-PCR) or tissue metabolite levels. The brain was removed and regionally dissected (Bernier et al 2008) to isolate the POA and the hypothalamus. Whole pituitary and liver, and a standardized sample of white muscle (rostral to dorsal fin) were also collected.…”

“…After development of the radiographs, the number of steel beads in the gastrointestinal tract was tallied and the amount of feed consumed calculated using a calibration curve. Plasma analyses Plasma cortisol concentrations were measured in triplicate by RIA as per the methods of Bernier et al (2008). The lower detection of the assay was 16 pg/ml.…”

Differential effects of chronic hypoxia and feed restriction on the expression of leptin and its receptor, food intake regulation and the endocrine stress response in common carp

“…The brain, whole pituitary and liver were also collected to quantify the mRNA levels of several genes. The brain was regionally dissected to isolate the hypothalamus and the pre-optic area (POA) as per Bernier et al (Bernier et al, 2008). All tissues were immediately frozen in liquid nitrogen and stored at -80°C for future analysis.…”

Effect of different glycaemic conditions on gene expression of neuropeptides involved in control of food intake in rainbow trout; interaction with stress

“…Analyses were performed on 1l of the diluted cDNA [further dilution 1/25 for elongation factor 1-alpha (EF1) and 1/4 for POMC] using the ABsolute TM qPCR SYBR ® Green Mix (Abgene, Cambridge, UK), in a total PCR reaction volume of 15l, containing 50 to 500nmoll -1 of each primer. GK (Panserat et al, 2000), POMC1 (Leder and Silverstein, 2006), EF1 (Bernier et al, 2008) and CRF (Bernier et al, 2008) qPCRs were performed using primers previously described. Primers for NPY were designed according to the available sequence in public databases (GenBank accession number NM_001124266).…”

“…The changes in the activity of glucosensor systems, as well as in the food intake response, might be related to an altered expression of orexigenic or anorexigenic factors in the same areas owing to the interaction between different glycaemic conditions and stress. Several studies have reported changes in the expression of peptides in several brain areas when fish were exposed to stress conditions such as decreased corticotrophin-releasing factor (CRF) and increased NPY expression in the preoptic area of goldfish (Bernier et al, 2004), increased CRF expression in the forebrain (Bernier and Craig, 2005) and preoptic area (Bernier et al, 2008) of rainbow trout and decreased POMC expression in the brain of sole Solea solea (Palermo et al, 2008). However, there are no studies available in the literature regarding changes in the expression of the same peptides under different glycaemic conditions when fish are simultaneously exposed to a stressful situation.…”