Aromatase regulates aggression in the African cichlid fish Astatotilapia burtoni

• Published in: Physiology & behavior Vol. 112; pp. 77 - 83
• Main Authors: Huffman, Lin S, O’Connell, Lauren A, Hofmann, Hans A
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 15-03-2013; Elsevier
• Subjects: Aggression; Aggression - drug effects; Aggression - physiology; Animals; Aromatase; Aromatase - genetics; Aromatase - metabolism; Aromatase Inhibitors - pharmacology; Astatotilapia; Behavioral psychophysiology; Biological and medical sciences; Brain - drug effects; Brain - enzymology; Cichlids - metabolism; Cichlids - physiology; Dose-Response Relationship, Drug; Drug Delivery Systems; estradiol; Estradiol - blood; Estrogen; Fadrozole; Fadrozole - pharmacology; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Enzymologic - drug effects; Hierarchy, Social; Male; males; preoptic area; Preoptic Area - drug effects; Preoptic Area - metabolism; Psychiatry; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Reproduction - drug effects; reproductive behavior; social behavior; Statistics, Nonparametric; Testosterone; Testosterone - blood; Fadrozole; Testosterone; Aggression; Aromatase; Estrogen; Antineoplastic agent; Imidazole derivatives; Androgen; Enzyme; Enzyme inhibitor; Estrogen synthase; Ovarian hormone; African; Testicular hormone; Sex steroid hormone; Non steroid compound
• ISSN: 0031-9384; 1873-507X
• DOI: 10.1016/j.physbeh.2013.02.004

Abstract The roles of estrogen and androgens in male social behavior are well studied, but little is known about how these hormones contribute to behavior in a social hierarchy. Here we test the role of aromatase, the enzyme that converts testosterone into estradiol, in mediating aggression and reproductive behavior in male Astatotilapia burtoni , an African cichlid fish that displays remarkable plasticity in social behavior. We first measured aromatase expression in subordinate and dominant males in brain regions that regulate social behavior and found that subordinate males have higher aromatase expression than dominant males in the magnocellular and gigantocellular regions of the preoptic area. Next, we functionally tested the role of aromatase in regulating behavior by intraperitoneally injecting dominant males with either saline or fadrozole (FAD), an aromatase inhibitor, and found that FAD treatment decreases aggressive, but not reproductive, behaviors compared to saline controls. To determine the underlying physiological and molecular consequences of FAD treatment, we measured estradiol and testosterone levels from plasma and brain aromatase expression in FAD and saline treated dominant males. We found that estradiol levels decreased and testosterone levels increased in response to FAD treatment. Moreover, FAD treated males had increased aromatase expression in the gigantocellular portion of the POA, possibly a compensatory response. Overall, our results suggest aromatase is a key enzyme that promotes aggression in A. burtoni males through actions in the preoptic area.