title: Identification of a pheromone that increases anxiety in rats.
abstract: Chemical communication plays an important role in the social lives of various mammalian species. Some of these chemicals are called pheromones. Rats release a specific odor into the air when stressed. This stress-related odor increases the anxiety levels of other rats; therefore, it is possible that the anxiety-causing molecules are present in the stress-related odorants. Here, we have tried to identify the responsible molecules by using the acoustic startle reflex as a bioassay system to detect anxiogenic activity. After successive fractionation of the stress-related odor, we detected 4-methylpentanal and hexanal in the final fraction that still possessed anxiogenic properties. Using synthetic molecules, we found that minute amounts of the binary mixture, but not either molecule separately, increased anxiety in rats. Furthermore, we determined that the mixture increased a specific type of anxiety and evoked anxiety-related behavioral responses in an experimental model that was different from the acoustic startle reflex. Analyses of neural mechanisms proposed that the neural circuit related to anxiety was only activated when the two molecules were simultaneously perceived by two olfactory systems. We concluded that the mixture is a pheromone that increases anxiety in rats. To our knowledge, this is the first study identifying a rat pheromone. Our results could aid further research on rat pheromones, which would enhance our understanding of chemical communication in mammals.
authors.affiliation: Laboratory of Veterinary Ethology, Department of Animal Resource Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan;
authors.forename: Hideaki
authors.initials: H
authors.lastname: Inagaki
authors.affiliation: Laboratory of Veterinary Ethology, Department of Animal Resource Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan;
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Kiyokawa
authors.affiliation: Technical Research Institute, T. Hasegawa Co., Ltd., Kawasaki-shi, Kanagawa 211-0022, Japan; and.
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Tamogami
authors.affiliation: Laboratory of Organic Chemistry, Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Hidenori
authors.initials: H
authors.lastname: Watanabe
authors.affiliation: Laboratory of Veterinary Ethology, Department of Animal Resource Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan; aytake@mail.ecc.u-tokyo.ac.jp.
authors.forename: Yukari
authors.initials: Y
authors.lastname: Takeuchi
authors.affiliation: Laboratory of Veterinary Ethology, Department of Animal Resource Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan;
authors.forename: Yuji
authors.initials: Y
authors.lastname: Mori
mesh_terms: D000447:Aldehydes / Q000737:chemistry / Q000494:pharmacology; D000818:Animals; D001007:Anxiety / Q000139:chemically induced / Q000503:physiopathology; D001522:Behavior, Animal / Q000187:drug effects*; D002208:Caproates / Q000737:chemistry / Q000494:pharmacology; D008297:Male; D009830:Olfactory Bulb / Q000503:physiopathology; D010675:Pheromones / Q000737:chemistry / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013216:Reflex, Startle / Q000187:drug effects*
chemical_list: D000447:Aldehydes; D002208:Caproates; D010675:Pheromones; C018575:isocaproaldehyde; C010463:n-hexanal
keywords: acoustic startle reflex; alarm pheromone; anxiety; rat; stress-related odor