Adolescent anabolic-androgenic steroid exposure alters lateral anterior hypothalamic serotonin-2A receptors in aggressive male hamsters

Chronic anabolic-androgenic steroid (AAS) treatment during adolescence facilitates offensive aggression in male Syrian hamsters (Mesocricetus auratus). Serotonin (5-HT) modulates aggressive behavior and has been shown to be altered after chronic treatment with AAS. Furthermore, 5-HT type 2 receptors have been implicated in the control of aggression. For example, treatment with 5-HT2A receptor antagonists suppress the generation of the offensive aggressive phenotype. However, it is unclear whether these receptors are sensitive to adolescent AAS exposure. The current study assessed whether treatment with AAS throughout adolescence influenced the immunohistochemical localization of 5-HT2A in areas of the hamster brain implicated in the control of aggression. Hamsters were administered AAS (5.0 mg/kg) each day throughout adolescence, scored for offensive aggression, and then examined for differences in 5-HT2A-immunoreactivity (5-HT2A-ir). When compared with non-aggressive oil-treated controls, aggressive AAS-treated hamsters showed significant increases in 5-HT2A-ir fibers in the lateral portion of the anterior hypothalamus (LAH). Further analysis revealed that AAS treatment also produced a significant increase in the number of cells expressing 5-HT2A-ir in the LAH. Together, these results support a role for altered 5-HT2A expression and further implicate the LAH as a central brain region important in the control of adolescent AAS-induced offensive aggression.