Nandrolone, an anabolic androgenic steroid, reduced delta opioid receptor (DOR) mRNA and the number of DOR binding sites in two neuronal hybrid cell lines: NG 108-15 and the GT1-1 cells. Both cell lines express DOR but only GT1-1 cells express androgen receptors (AR). DOR mRNA levels were maximally decreased by ∼45% in NG 108-15 cells and by ∼38% in GT1-1 cells exposed for 24 h to 10−6M nandrolone. This action was partly due to a decrease in the rate of transcription of DOR mRNA and was not blocked by the androgen antagonist flutamide. Flutamide antagonized the repression of AR mRNA induced by nandrolone. The synthetic glucocorticoid dexamethasone (10−6M) did not modify DOR steady-state transcripts in either cell line. These results suggest that nandrolone presumably regulate DOR mRNA levels through mechanisms independent of the androgen and glucocorticoid receptors.