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.stress-related odor | alarm pheromone | acoustic startle reflex | anxiety | rat C hemical communication plays an important role in the social lives of various mammalian species. Some of these chemicals are called "pheromones." Because the term pheromone was coined and defined based on findings in insects (1), there is still a debate as to whether the original definition can be applied to mammals (2). Researchers have proposed revised definitions by modifying the original definition and/or specifying additional requirements (3-6). On the basis of the original and revised definitions, we set a working definition of pheromone within this study as (i) substances that are secreted to the outside by an individual and received by a second individual of the same species, in which they cause a specific reaction; (ii) substances that are effective in minute amounts; (iii) substances that are released from living individuals; and (iv) substances that mediate communication for an evolutionarily adaptive function.Rats release a specific odor into the air when stressed (7). This stress-related odor increases anxiety levels (8, 9) and induces a variety of anxiety-related responses depending on their situation with other rats (9-18). Rats respond to their own stressrelated odor in a similar manner to odor released from the other rats, suggesting that the odor has general effects (10,19). In addition, the stress-related odor appears to be effective in minute amounts (20,21). Therefore, the molecules responsible for increasing anxiety levels should exist in the...

Pheromone signals regulate conspecific behavior and physiology [1]. Releaser pheromones induce specific behavior by exerting acute effects on the neuronal response, whereas primer pheromones induce physiological changes with long-lasting effects by changing the neuroendocrine status of the recipients. In mammals, although several types of releaser pheromones have been identified [2-5], the identities of primer pheromones, as well as their mechanisms of action, remain largely unknown [6]. In sheep and goats, the seasonally anestrous endocrine state of females is changed to the estrous state upon exposure to male scents [7, 8]. This so-called "male effect" is one of the most conspicuous primer pheromone effects in mammals [9, 10]. In this study, we have identified an olfactory signal molecule that activates the central regulator of reproduction, the gonadotropin-releasing hormone (GnRH) pulse generator, in goats. Using gas chromatography-mass spectrometry to analyze male goat headspace volatiles, we identified several ethyl-branched aldehydes and ketones. We electrophysiologically demonstrated that one of these compounds, 4-ethyloctanal, activates the GnRH pulse generator in female goats. This is the first report of an olfactory molecule that has been shown to activate the central reproductive axis, and this discovery will provide a new direction for primer pheromone research.

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We report that the abdomen and associated tissues are the predominant sources of

In order to overcome the limitations of the methodology for the separation of enantiomers in GLC analysis, we successfully developed a novel GLC column named 'Chiramix', coated with a mixture of two chiral stationary phases, heptakis-(2,6-di-O-methyl-3-O-pentyl)-ˇ-cyclodextrin (2,6-Me-3-Pe-ˇ-CD) and octakis-(2,6-di-O-methyl-3-O-trifluoroacetyl)--cyclodextrin (2,6-Me-3-TFAc--CD). It was proved that the 'Chiramix' column is greatly superior to those with a single chiral phase for separating enantiomers of compounds with various functional groups. As a successful example, this was applied to the analysis of multicomponent systems, such as peach flavours, and the enantiomeric purities of several components of monoterpene hydrocarbons, alcohols, ketones and lactones were determined exactly and simultaneously.