Effects of acute exposure to exogenous ammonia on cerebral monoaminergic neurotransmitters in juvenile Solea senegalensis

Abstract

The present study explored the potential role of brain catecholaminergic and serotoninergic systems as neuronal targets for the toxicological effects of acute ammonia exposure (0.28 mg l(-1) of un-ionized ammonia for 12 and 24 h) in juvenile sole (Solea senegalensis). In addition, plasma cortisol levels were measured. The results showed significant increases in their concentrations that were similar after 12 and 24 h of exposure. These data indicate that acute exposure (12 and 24 h) to ammonia initiates a typical stress response in the Senegalese sole, with stimulation of the hypothalamus-pituitary-interrenal axis. The concentrations of dopamine (DA), serotonin (5-hydroxytryptamine; 5-HT) and noradrenaline (NA), and their metabolites, 3, 4-dihydroxyphenylacetic acid (DOPAC) and 5-hydroxy-3-indoleacetic acid (5HIAA), were measured in the hypothalamus, telencephalon and optic tectum. The main changes induced by acute exposure to ammonia were decreases in the concentrations of 5-HT and DA, which were significant in most of the brain regions studied. The ratios of 5-HIAA/5-HT and DOPAC/DA increased in all regions and at all times studied, although in the case of the DOPAC/DA ratio, the increases were only significant in the hypothalamus (24 h exposure) and in the optic tectum (12 and 24 h exposure). These changes indicated that exposure to ammonia elicited time-dependent increases in serotoninergic and dopaminergic activity in the hypothalamus, telencephalon and optic tectum.

The response of brain serotonergic and dopaminergic systems to an acute stressor in rainbow trout: a time-course study

“…The initial activation of the brain monoaminergic neurons could be part of the stressor recognition mechanisms, taking part in the central integration of the stress signals to initiate the neuroendocrine response. The observed peaks in both hypothalamic and telencephalic serotonergic activities 45 min after stress could be the result of the indirect effects of other participants in the stress response such as cortisol, which is known to promote serotonergic activity in fish (Summers and Winberg, 2006;Weber et al, 2012). It is known that the regulation of the serotonergic neuronal system is different in cases of chronic stress, where the activation seems to be more permanent (Øverli et al, 2005; Øverli et al, 2007).…”

“…In mammals, both stimulatory and inhibitory effects of stress on dopaminergic activity have been reported (Höglund et al, 2001;Waters et al, 2005). In fish, although several studies have reported a stimulatory action of different kinds of stressors on the central dopaminergic system (Backström et al, 2011;Gesto et al, 2008;Øverli et al, 1999;Weber et al, 2012), such stimulation did not always take place (M.G. and J.M.M., unpublished observations).…”

“…The role of most of these elements is well known, whereas the function of some others, such as the brain monoaminergic neurotransmitters, is not yet clear. For instance, the activity of central monoaminergic systems increases after exposure to different types of stressors, such as handling, isolation, predator exposure, pollutant exposure or crowding (Gesto et al, 2008;Gesto et al, 2009;Schjolden et al, 2006;Weber et al, 2012;Winberg and Nilsson, 1993), with the response of the serotonergic activity being especially consistent. However, the causes and consequences of these increased activities within the stress response along with the dynamics of the monoaminergic response to stress are not well known.…”

Effects of acute handling stress on cerebral monoaminergic neurotransmitters in juvenile Senegalese sole Solea senegalensis

“…Compared with the numerous studies that have addressed the effect of stress factors on serotoninergic and catecholaminergic systems in mammals, relatively few such studies have been carried out with fishes, and most of the existing studies have focused on the effect of social stress or stress associated with exposure to toxic chemicals. Thus, increased brain serotoninergic and dopaminergic activity have been observed in salmonids subjected to social stress (Winberg & Nilsson, ; Winberg & Lepage, ; Øverli et al , ; Cubitt et al , ) and in salmonids and Senegalese sole Solea senegalensis (Kaup 1858) subjected to stress induced by exposure to toxic chemicals (Gesto et al , ; Weber et al , ). A recent study has also shown that acute handling stress induces a rapid increase in serotoninergic and dopaminergic activity in the telencephalon of rainbow trout Oncorhynchus mykiss (Walbaum 1792) (Gesto et al , ).…”

Acute toxicity of ammonia and nitrite to different ages of Pacific cod (Gadus macrocephalus) larvae

“…Ammonia and nitrite are toxic to fish. [11][12][13][14][15][16][17][18][19][20] Weber et al [21] discovered that the brain dopaminergic and serotonergic systems are neuronal targets for the toxicological effects of acute ammonia exposure. Miron et al [22] found that exposure to ammonia increased the total ammonia levels in tissues and damaged the gill epithelium in juvenile silver catfish, Rhamdia quelen (Heptapteridae).…”