P. Johansson et al., ANABOLIC-ANDROGENIC STEROIDS INCREASE BETA-ENDORPHIN LEVELS IN THE VENTRAL TEGMENTAL AREA IN THE MALE-RAT BRAIN, Neuroscience research, 27(2), 1997, pp. 185-189
The levels of beta-endorphin and Met-enkephalin-Arg-Phe (MEAP) immunor
eactivity in various brain regions (including amygdala, cortex, hippoc
ampus, hypothalmus, nucleus accumbens, pituitary and ventral tegmental
area) were studied in male rats subjected to dialy intramuscular inje
ctions during 14 days of high doses (5 and 15 mg/kg) of ths anabolic a
ndrogenic steroid (AAS), nandrolone decanoate. At the nandrolone dose
of 15 mg/kg a significant (about 20-fold) increase in beta-endorphin l
evels in the ventral tegmental area (VTA) was observed. The steroid di
d not significantly affect the concentration of the peptide at any dos
e in other brain areas examined. The levels of MEAP remained unaltered
in all studied regions. A slight increase in serum concentrations of
both peptides was also found but this elevation was not statistically
significant. The observed increase in beta-endorphin in VTA iras sugge
sted to be involved in a mechanism by which the steroid may influence
the reward system in the brain. An opioid mediated stimulation of the
reward system following injection of AAS supports a previous hypothesi
s that AAS may induce psychological dependence. (C) 1997 Elsevier Scie
nce Ireland Ltd.