The effect on opioid peptides in the rat brain, after chronic treatment with the anabolic androgenic steroid, nandrolone decanoate

In recent years, an increase in abuse of anabolic androgenic steroids (AAS) has been seen among individuals not directly connected to sports. Clinical evidence suggests that abuse of these steroids may result in profound chan ges in personality, expressed by depressive symptoms, irritability and incr eased aggression. It is still unknown whether these alterations are related to changes in any particular transmitter system or whether they are persis tent or reversible. In this study we focused on AAS effect on the endogenou s dynorphin and enkephalin system in the brain. Male rats were given intram uscular injections of the AAS nandrolone decanoate (15 mg/kg), once daily f or 2 weeks. The levels of the opioid peptide immunoreactivities (ir) were a ssessed by radioimmunoassay in two groups immediately after the treatment a nd in two other groups after additional 3 weeks without any drug treatment (recovery period). The result indicates that chronic AAS treatment increase d the activity in the dynorphin B- and Met-enkephalin-Arg(6)Phe(7)-ir in th e hypothalamus, striatum and periaqueductal gray (PAG) compared to controls . In addition, the steroid induced an imbalance between the dynorphin and t he enkephalin opioid system in the nucleus accumbens, hypothalamus and PAG. This imbalance remained after the recovery period, Since increased peptide activity was found in brain regions regulating emotions, dependence, defen sive reactions and aggression, it was suggested that the actual endogenous opioid systems are involved in previously reported AAS-induced changes in t hese behaviours. (C) 2000 Elsevier Science Inc.