Résumé
Trilostane is a competitive inhibitor of 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD), which notably converts pregnenolone into progesterone or dehydroepiandrosterone into androstenedione. Trilostane shows antidepressant-like properties in the forced swimming test (FST). The compound, however, induced only moderate effects on neuroactive steroid levels that could be related to its behavioral efficacy.
We compared the behavioral effect of trilostane with the other 3 beta-HSD inhibitor, cyanoketone, and analyzed the putative involvement of the beta-type estrogen receptor (ER beta) in its antidepressant effect.
Trilostane reduced immobility in the FST significantly at 12.5 and 25 mg/kg subcutaneously (s.c.), whereas cyanoketone (0-100 mg/kg s.c.) was ineffective. The negative ER modulator fulvestrant (ICI 182780) dose-dependently blocked the effect of trilostane (25 mg/kg). Trilostane increased circulating estradiol levels in the 12.5-50 mg/kg dose-range, and this effect was unaffected by stress and not shared by cyanoketone (25 mg/kg). The trilostane (25 mg/kg) treatment increased the ER beta mRNA expression in adrenals (+100%) and centrally, in the hippocampus (+330%). Stress and cyanoketone failed to affect ER beta mRNA levels in periphery or in the brain.
These data demonstrate that the antidepressant-like potential of trilostane is not due to its 3 beta-HSD inhibiting activity, since it is not shared by cyanoketone, but rather to its estrogenic activity. The compound, which releases estradiol and up-regulates ER beta receptors, could be used as a therapeutic tool to allow an estrogenic facilitation of antidepressant efficacy.