Effects of an anabolic-androgenic steroid on the regulation of the NMDA receptor NR1, NR2A and NR2B subunit mRNAs in brain regions of the male rat

The expression of the N-methyl- d-aspartate (NMDA) receptor subunits NR1, NR2A and NR2B mRNAs was examined in discrete areas of the male rat brain (including hippocampus, hypothalamus, nucleus accumbens and cortex) following 14 days daily intramuscular injections of high doses (5 and 15 mg/kg) of an anabolic-androgenic steroid (AAS) (nandrolone decanoate). The results indicated that the drug produced a significant decrease in the mRNA expression of the NR2A receptor subunit both in the hypothalamus and hippocampus. A decrease in the level of NR2B receptor mRNA was observed in hypothalamus at the lower dose of the AAS but in other areas examined, this receptor subunit mRNA was not affected. Except for a decreased expression in the nucleus accumbens at the higher dose of AAS the NR1 receptor subunit mRNA was not affected by the drug. The three subunit mRNAs in cortex were not significantly altered. The effects of the steroid on the mRNA expression for the NMDA receptor subunits in hippocampus and hypothalamus are suggested to be involved in the mechanism behind aggressive behaviour, a feature previously associated with AAS misuse. The downregulation of the mRNA for the NR1 receptor subunit in nucleus accumbens may relate to a mechanism involved in the recently suggested AAS-induced stimulation of the brain reward system.