DIFFERENT TYPES OF STEROIDS INHIBIT [H-3]DIPRENORPHINE BINDING IN MOUSE-BRAIN MEMBRANES

1. The binding of 60 drugs, mainly steroids, to opioid receptors was s tudied in crude membrane fractions from mouse brains. 2. Competition a ssays with the different drugs (5 x 10(-7)-10(-4) M) were performed by labeling opiate receptors with [H-3]diprenorphine (0.3-0.4 nM). 3. On ly 7 drugs (alpha,5 beta-tetrahydrodeoxycorticosterone, megestrol acet ate, mifepristone, 17 alpha-ethynlestradiol, diethylstilbestrol, clomi phene citrate and tamoxifen citrate) inhibited [H-3]diprenorphine bind ing more than 50% at the highest concentration assayed (10(-4) M). The IC50 values ranged between 6 x 10(-5) M. 4. Thus, the present results show that only a limited number of steroids, from diverse classes, bi nd to opiate receptors. (C) 1998 Elsevier Science Inc.