Dried Nardostachys chinensis roots contain sesquiterpenoids that are widely used as herbal tranquilizers. We previously identified the highly sedative sesquiterpenoid valerena-4,7(11)-diene (VLD) from this plant. In the present study, we investigated stress reducing effects of VLD and the associated mechanisms of action. Application of 15-min restraint stresses induced excitatory behaviors in mice. Immobility times in the forced swim test and sleeping times in the pentobarbital sleep test were shortened in the stressed group by 47% and 43%, respectively, compared with the control group. Furthermore, restraint stress increased serum corticosterone levels by 75%, and cerebral serotonin (5-HT) and dopamine (DA) levels. Inhaled VLD (300 mu g/cage) suppressed stress-induced excitatory behaviors and significantly reduced stress-induced blood corticosterone, cerebral 5-HT, and DA levels. These results suggest that VLD interacts with the hypothalamic pituitary adrenal axis and the sympathetic-adrenomedullary system. These interactions appear to involve GABAergic and D, antagonist activities. Moreover, tests in anosmic and intravenously treated mice showed that the sedative effect of inhaled VLD was expressed via olfactory stimulation and pulmonary absorption. Although more studies are required to further elucidate the properties of this compound, our studies suggest that VLD may be an effective anti-stress aromatherapy for humans.