Identification of an Olfactory Signal Molecule that Activates the Central Regulator of Reproduction in Goats

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. [Display omitted] •Ethyl-branched aldehydes and ketones were isolated from male goat headspace volatiles•One of these molecules, 4-ethyloctanal, activates the reproduction center•This molecule is the primer pheromone responsible for the male effect in goats Murata et al. report the identification of a male goat-specific olfactory signal molecule, 4-ethyloctanal, which activates the reproduction center of the female perceiving this molecule. This is the first evidence of a primer pheromone molecule with central action in mammals.