γ-Oryzanol Ameliorates Depressive Behavior in Ovariectomized Mice by Regulating Hippocampal Nitric Oxide Synthase: A Potential Therapy for Menopausal Depression.

Abstract

Depression is a severe mental condition, common among menopausal women. γ-Oryzanol (ORY) has various biological properties; however, the effect of ORY on menopausal depression and its underlying mechanisms have not been investigated. ORY is orally administered to ovariectomized (OVX) mice for 20 weeks. ORY administration results in lower immobility time in the tail suspension and forced swim test and increases locomotor activity in the open field test. In the primary hippocampal neurons and hippocampi of OVX mice, ORY treatment increases nitric oxide (NO) production and neuronal NO synthase (nNOS) expression. Further, the phosphorylation of extracellular signal-regulated kinase (ERK), cAMP response element-binding protein (CREB), and tropomyosin receptor kinase B, along with the expression of brain-derived neurotrophic factior (BDNF), is upregulated. These stimulatory effects of ORY are diminished by treatment with estrogen receptor β (ERβ) antagonist. ORY similarly interacts with ERβ in the molecular docking analysis. Moreover,intracerebroventricular injection of 7-nitroindazole, a nNOS inhibitor, abolishes the antidepressant effects of ORY. The results indicate that ORY attenuates depressive behavior in OVX mice by upregulating ERβ-mediated hippocampal nNOS expression and activating the ERK-CREB-BDNF signaling networks. The findings suggest that ORY is a potential therapeutic agent for attenuating menopausal depression.