title: Alarm pheromone does not modulate 22-kHz calls in male rats.
abstract: Rats are known to emit a series of ultrasonic vocalizations, termed 22-kHz calls, when exposed to distressing stimuli. Pharmacological studies have indicated that anxiety mediates 22-kHz calls in distressed rats. We previously found that exposure to the rat alarm pheromone increases anxiety in rats. Therefore, we hypothesized that the alarm pheromone would increase 22-kHz calls in pheromone-exposed rats. Accordingly, we tested whether exposure to the alarm pheromone induced 22-kHz calls, as well as whether the alarm pheromone increased 22-kHz calls in response to an aversive conditioned stimulus (CS). Rats were first fear-conditioned to an auditory and contextual CS. On the following day, the rats were either exposed to the alarm pheromone or a control odor that was released from the neck region of odor-donor rats. Then, the rats were re-exposed to the aversive CS. The alarm pheromone neither induced 22-kHz calls nor increased 22-kHz calls in response to the aversive CS. In contrast, the control odor unexpectedly reduced the total number and duration of 22-kHz calls elicited by the aversive CS, as well as the duration of freezing. These results suggest that the alarm pheromone does not affect 22-kHz calls in rats. However, we may have found evidence for an appeasing olfactory signal, released from the neck region of odor-donor rats.
authors.affiliation: Laboratory of Veterinary Ethology, The University of Tokyo, Tokyo, Japan. Electronic address: muyamahi@gmail.com.
authors.forename: Hiromi
authors.initials: H
authors.lastname: Muyama
authors.affiliation: Laboratory of Veterinary Ethology, The University of Tokyo, Tokyo, Japan. Electronic address: akiyo@mail.ecc.u-tokyo.ac.jp.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Kiyokawa
authors.affiliation: Center for Animal Research and Education, Nagoya University, Nagoya, Japan. Electronic address: inagaki@care.nagoya-u.ac.jp.
authors.forename: Hideaki
authors.initials: H
authors.lastname: Inagaki
authors.affiliation: Laboratory of Veterinary Ethology, The University of Tokyo, Tokyo, Japan. Electronic address: aytake@mail.ecc.u-tokyo.ac.jp.
authors.forename: Yukari
authors.initials: Y
authors.lastname: Takeuchi
authors.affiliation: Laboratory of Veterinary Ethology, The University of Tokyo, Tokyo, Japan. Electronic address: aymori@mail.ecc.u-tokyo.ac.jp.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Mori
mesh_terms: D000161:Acoustic Stimulation; D000818:Animals; D001007:Anxiety; D001522:Behavior, Animal / Q000502:physiology*; D003213:Conditioning, Psychological / Q000502:physiology; D005239:Fear / Q000502:physiology; D008297:Male; D010675:Pheromones; D051381:Rats; D014465:Ultrasonics / Q000379:methods; D014828:Vocalization, Animal / Q000502:physiology*
chemical_list: D010675:Pheromones
keywords: 22-kHz calls; Alarm pheromone; Fear conditioning; Ultrasonic vocalizations