Chronic nandrolone administration induces dysfunction of the reward pathway in rats

Data in animal models and surveys in humans have revealed psychiatric complications of long-term anabolic androgenic steroid abuse. However, the neurobiochemical mechanisms behind the observed behavioral changes are poorly understood. The aim of the present study was to investigate the effects of nandrolone decanoate on emotional behavior and neurochemical brain alterations in gonadally intact male rats. The behavioral reactivity to the elevated plus maze and the social interaction test was used to assess anxiety-related symptoms, and the sucrose preference test was used to evaluate anhedonia. Dopaminergic, serotonergic and noradrenergic transmissions were also evaluated in selected brain areas. The chronic administration of nandrolone, at 5 mg kg(-1) injected daily for 4 weeks, induced the loss of sweet taste preference, a sign of anhedonia and dysfunction of the reward pathway. The behavioral outcomes were accompanied by reductions in the dopamine, serotonin and noradrenaline contents in the nucleus accumbens. Alterations in the time spent in the open arms and in the social interaction test were not found, suggesting that nandrolone did not induce an anxiogenic profile. No differences were revealed between the experimental groups in the amygdala in terms of the neurotransmitters measured. Our data suggest that nandrolone-treated rats have a depressive, but not anxiogenic-like, profile, accompanied by brain region-dependent changes in dopaminergic, serotonergic and noradrenergic neurotransmission. As anabolic androgenic steroid dependence is plausibly the major form of worldwide substance dependence that remains largely unexplored, it should be highlighted that our data could contribute to a better understanding of the altered rewards induced by nandrolone treatment and to the development of appropriate treatments.