Abstract
Stress induces various neurobiological responses and causes psychiatric disorders, including depression. Monoamine oxidase A (MAO-A) plays an important role in various functions of the brain, such as regulation of mood, anxiety and aggression, and dysregulation of MAO-A is observed in stress-related psychiatric disorders. This study addressed the question whether acute social stress induces changes to transcriptional and/or post-transcriptional regulation of MAO-A expression in the brain. Using male Nile tilapia (Oreochromis niloticus), we investigated whether acute social stress, induced by the presence of a dominant male fish, changes the expression of MAO-A. We measured gene expression of MAO-A by quantitative PCR, enzymatic activity of MAO-A by the luminescent method, and 5-HT and 5-HIAA levels by liquid chromatography–mass spectrometry in the brain of socially stressed and control fish. Socially stressed males showed decreased MAO-A mRNA levels, consistent MAO-A enzymatic activity, increased 5-HT turnover in the brain, and elevated plasma cortisol levels, compared to controls. Our results suggest that acute social stress suppresses the transcription of MAO-A gene, enhances 5-HT metabolism but does not affect the production of MAO-A protein.
Highlights
Stress elicits various neurobiological responses and causes several psychiatric disorders, including depression, anxiety disorder, and post-traumatic stress disorder (Lucassen et al, 2014; Chiritã et al, 2015)
In this study, using male Nile tilapia (Oreochromis niloticus), we studied whether acute social stress induces responses in the regulation of monoamine oxidase A (MAO-A) by measuring the gene expression and enzymatic activity of MAO-A, and 5-HT turnover
Plasma cortisol levels were significantly higher in social stress group, compared to control groups [p < 0.01 for 2.5 h social stress (111.9 ng/mL) vs. control (28.9 ng/mL); p < 0.01 for 5 h social stress (139.3 ng/mL) vs. control (10.7 ng/mL); Figure 1C]
Summary
Stress elicits various neurobiological responses and causes several psychiatric disorders, including depression, anxiety disorder, and post-traumatic stress disorder (Lucassen et al, 2014; Chiritã et al, 2015). Dysregulation of monoamine oxidase A (MAO-A) is observed in stress-related psychiatric disorders. Elevated MAO-A activity and 5-hydroxytryptamine (5-HT) degradation in the brain are well-known features in depressed patients and animals exposed to chronic stress. Positron emission tomography shows higher density of MAO-A in the brain of patients with major depressive disorders, compared to healthy subjects (Meyer et al, 2006). Higher MAO-A density in the brain is associated with the recurrence of depressive symptoms. MAO-A Expression During Social Stress (Meyer et al, 2009). Chronically stressed animals show increased MAO-A levels, decreased 5-HT levels, and elevated 5-hydroxyindoleacetic acid (5-HIAA) levels (Winberg and Lepage, 1998; Grunewald et al, 2012)
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