High Stocking Density and Food Deprivation Increase Brain Monoaminergic Activity in Gilthead Sea Bream (Sparus aurata)

Abstract

In teleosts, brain monoamines (dopamine and serotonin) participate in the early response to different acute stressors. However, little is known regarding their role during chronic stress. In a 2 × 2 factorial design, the influence of a high stocking density (HSD) and/or food deprivation (FD) on the brain monoaminergic activity in gilthead sea bream (Sparus aurata) was evaluated. Following a 21-day experimental design, samples from the plasma and brain regions (telencephalon, hypothalamus, and optic tectum) were collected. The dopamine (DA), serotonin (5HT), and their main metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and 5 hydroxyindoleacetic acid (5HIAA), contents were HPLC-assessed in brain tissues, and the ratios DOPAC/DA and 5HIAA/5HT were calculated as indicators of enhanced monoaminergic activity. The plasma levels of cortisol and catecholamine were also evaluated. The cortisol levels increased in fish exposed to HSD and normally fed but, also, in all FD groups, whereas the NA levels decreased in LSD-FD animals. Within the brain, the dopaminergic and serotonergic activities in telencephalon and hypothalamus increased in fish subjected to HSD and in the telencephalon of LSD-FD fish. While DA (hypothalamus) and 5HT (telencephalon) increased in the animals submitted to a HSD, food-deprived fish did not show such an increase. Taken together, our results supported the hypothesis of brain monoaminergic activity participating in maintaining and orchestrating the endocrine response to chronic stress in fish.

Cohabitation With Atlantic Salmon (Salmo salar) Affects Brain Neuromodulators But Not Welfare Indicators in Lumpfish (Cyclopterus lumpus)

“…Furthermore, based on the results of this and a previous study ( Staven et al, 2021 ), the social factor was likely the most important. Social factors were considered the most relevant because stress related alterations in the brain monoaminergic systems are usually more prominent in the serotonergic than in the dopaminergic system, both in situations of acute and prolonged stress ( Øverli et al, 2001 ; Gesto et al, 2013 ; Conde-Sieira et al, 2018 ; López-Patiño et al, 2021 ), and no alterations were found in the serotonergic system in this study. Furthermore, our previous study ( Staven et al, 2021 ) showed that both Live and Olfaction treatment were equally able to acutely modify the swimming activity of the lumpfish (in a kind of “startling” response), while only the Live treatment significantly affected the lumpfish brain in the current study.…”

Visual Perception of Density and Density-Dependent Growth in Medaka (Oryzias latipes): A Suitable Model for Studying Density Effects in Fish

“…ACTH enters the bloodstream and stimulates the synthesis and secretion of glucocorticoids in the steroidogenic cells of the interrenal gland (Spiess et al, 1981; Lederis et al, 1994; Bernier, 2006; Cerdá-Reverter et al, 2011; Gesto et al, 2013). Generally, elevated blood cortisol concentrations are observed among fish in a high-density environment, which is an extremely stressful condition (Liu et al, 2017; Long et al, 2019; López-Patiño et al, 2021). However, the results of this study revealed that the expression of pro-opiomelanocortin ( pomc ), the precursor of acth , decreased in the brains of highly stocked fish, and the transcription level of crh did not show a significant difference.…”

Grape pomace in diets for European sea bass: influence on oxidative status, intestinal microbiota, and fillet quality

“…Furthermore, data obtained on circulating cortisol levels revealed that either of the two experimental groups was not in a stressful situation judging by their low concentrations compared to several experimental models focused on the substitution or supplementation of different ingredients in aquaculture feeds, or even related to the basal levels considered normal recorded in other species including European sea bass (Montero et al 2015;Gorissen and Flik 2016;Schreck and Tort 2016;Samaras et al 2018;López-Patiño et al 2021). Although cortisol levels were low in both treatments, the slightly significant increase observed in control fish could be related to lower antioxidant capacity compared to fish fed the GP diet.…”