EFFECTS OF AN ANABOLIC-ANDROGENIC STEROID ON THE REGULATION OF THE NMDA RECEPTOR NR1, NR2A AND NR2B SUBUNIT MESSENGER-RNAS IN BRAIN-REGIONSOF THE MALE-RAT

The expression of the N-methyl-D-aspartate (NMDA) receptor subunits NR 1, NR2A and NR2B mRNAs was examined in discrete areas of the male rat brain (including hippocampus, hypothalamus, nucleus accumbens and cort ex) following 14 days daily intramuscular injections of high doses (5 and 15 mg/kg) of an anabolic-androgenic steroid (AAS) (nandrolone deca noate). The results indicated that the drug produced a significant dec rease 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. Ex cept for a decreased expression in the nucleus accumbens at the higher dose of AAS the NR1 receptor subunit mRNA was not affected by the dru g. The three subunit mRNAs in cortex were not significantly altered. T he 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 as sociated with AAS misuse. The downregulation of the mRNA for the NR1 r eceptor subunit in nucleus accumbens may relate to a mechanism involve d in the recently suggested AAS-induced stimulation of the brain rewar d system. (C) 1997 Elsevier Science Ireland Ltd.