The antidepressant-like effect of the 3β-hydroxysteroid dehydrogenase inhibitor trilostane involves a regulation of β-type estrogen receptors.

RATIONALE: Trilostane is a competitive inhibitor of 3β-hydroxysteroid dehydrogenase (3β-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.

METHODS

We compared the behavioral effect of trilostane with the other 3β-HSD inhibitor, cyanoketone, and analyzed the putative involvement of the β-type estrogen receptor (ERβ) in its antidepressant effect.

RESULTS

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 ERβ mRNA expression in adrenals (+100%) and centrally, in the hippocampus (+330%). Stress and cyanoketone failed to affect ERβ mRNA levels in periphery or in the brain.

CONCLUSIONS

These data demonstrate that the antidepressant-like potential of trilostane is not due to its 3β-HSD inhibiting activity, since it is not shared by cyanoketone, but rather to its estrogenic activity. The compound, which releases estradiol and up-regulates ERβ receptors, could be used as a therapeutic tool to allow an estrogenic facilitation of antidepressant efficacy.