title: Green odor and depressive-like state in rats: toward an evidence-based alternative medicine?
abstract: It is widely accepted that mental stress is an important factor in the development of psychological disorders such as depression. On pre-existing evidence, the so-called green odor may have a relieving and sedative effect on animals exposed to stressful situations. Using two behavioral models of depression, the forced-swim test and learned helplessness paradigm, we investigated whether inhalation of green odor (a 50:50 mixture of trans-2-hexenal and cis-3-hexenol) might alleviate and/or prevent experimentally induced depressive-like states in rats. A 3-min swim every day for 7 days resulted in significant prolongation of immobility time (vs. day 1). Inhaling green odor, but not vehicle, thereafter for 10 days (without swimming) led to the prolonged immobility time being significantly reduced and the hippocampal level of brain-derived neurotrophic factor (BDNF) being significantly increased. In the learned helplessness paradigm, the failure number and time spent in the shock compartment seen in the active avoidance test were both significantly attenuated in those rats that inhaled green odor for 11 days after the postshock screening test (vs. vehicle-exposed rats). Finally, for 10 consecutive days rats continuously exposed to green odor or vehicle swam for 3 min/day. Immobility time was significantly shorter in the green-odor group than in the vehicle-exposed group on days 6-10. These results suggest that green odor has not only a therapeutic, but also a preventive effect on depressive-like states in rats. These effects may be at least in part due to a green odor-induced upregulation of BDNF in the hippocampus.
authors.affiliation: Division of Integrative Physiology, Department of Functional, Morphological and Regulatory Science, Tottori University Faculty of Medicine, Yonago, Tottori 683, Japan. watanabe@med.tottori-u.ac.jp
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Watanabe
authors.forename: Miho
authors.initials: M
authors.lastname: Fujihara
authors.forename: Eri
authors.initials: E
authors.lastname: Murakami
authors.forename: Michio
authors.initials: M
authors.lastname: Miyoshi
authors.forename: Yuki
authors.initials: Y
authors.lastname: Tanaka
authors.forename: Satoshi
authors.initials: S
authors.lastname: Koba
authors.forename: Hiroto
authors.initials: H
authors.lastname: Tachibana
mesh_terms: D000280:Administration, Inhalation; D000818:Animals; D000929:Antidepressive Agents, Tricyclic / Q000494:pharmacology; D019341:Aromatherapy; D001362:Avoidance Learning / Q000187:drug effects; D001923:Brain Chemistry / Q000502:physiology; D019208:Brain-Derived Neurotrophic Factor / Q000096:biosynthesis / Q000378:metabolism; D020148:Butyric Acid / Q000494:pharmacology; D000529:Complementary Therapies; D003863:Depression / Q000523:psychology*; D019317:Evidence-Based Medicine; D006380:Helplessness, Learned; D006624:Hippocampus / Q000378:metabolism / Q000502:physiology; D007099:Imipramine / Q000494:pharmacology; D008297:Male; D009043:Motor Activity / Q000502:physiology; D009812:Odorants; D018515:Plant Leaves; D010944:Plants; D051381:Rats; D017208:Rats, Wistar; D013550:Swimming / Q000523:psychology
chemical_list: D000929:Antidepressive Agents, Tricyclic; D019208:Brain-Derived Neurotrophic Factor; D020148:Butyric Acid; D007099:Imipramine