Drugs acting on androgen receptors modify opioid transmission in the c
entral nervous system. To investigate a direct interaction, we studied
whether the binding of [H-3]diprenorphine to mouse brain membranes wa
s modified by cyproterone acetate (progesterone derivative with antian
drogen activity), flutamide (non-steroidal antiandrogen), 5 alpha-dihy
drotestosterone and progesterone. Only cyproterone acetate inhibited [
H-3]diprenorphine binding (IC50 = (1.62 +/- 0.33) x 10(-6) M) without
modifying its association rate. These results suggest that cyproterone
acetate binds to opiate receptors independently of its classical andr
ogenic intracellular receptor effect.