Tears don’t lie – Pheromones Drive Social Behavior

Together with international collaborative partners, RWTH professor, Marc Spehr, has published a study in the professional journal Nature on the influence of pheromones on the social behavior of mice. Pheromones play an important role in the social behavior of many animals. They facilitate information about the sex, reproduction cycle, state of health of other species members. In the study, researchers were able to prove that a newly discovered pheromone, ESP 22, delivers information about the age of mice. The study was conducted by Marc Spehr, Chair of a Lichtenberg Professorship and Head of the Department of Chemosensory, together with colleagues from Harvard University and the University of Tokyo.

 

The Scent of Youth

The pheromone is created based on age in the tear ducts of young mice. Upon reaching puberty, the creation of ESP22 dramatically reduces in mice three to four weeks old. In older animals the pheromone is not detectable. Not only was the age-dependent presence in tear fluid impressively documented in this study, but also the perception of this pheromone in the socalled vomeronasal organ and its effects on the behavior of mice.

The vomeronasal organ plays a crucial role in the perception of social signals in many animals. Professor Spehr's working group was able to show that individual nerve cells in mice's vomeronasal organs are responsible for the recognition of ESP22 and the further transfer of this signal to the brain. Although only a small part, one to two percent, of all nerve cells in vomeronasal organs are involved in the recognition of ESP22, the pheromone influences massive changes in the social behavior.

The scientists proved in experiments, that male mice with defective vomeronasal organs showed more sexual behavior towards young mice, just as other species members still producing ESP22 did. The impressive effect of the pheromone on sexual behavior was also demonstrated in the pubescent animals: When scientists marked the fur of adult female animals with ESP22, the number of pairing attemps by male species members dramatically decreased. Interestingly, ESP22 exclusively influences seuxal behavior and not other aspects of the mice's social interactions.

Neuronal Circuits

The results of this international study make it clear again how a sensory organ absent in humans encode pheromones and thus can have a direct influence of the complex social behavior of a group. Together with their American and Japanese colleagues, the Aachen biologists are already working on a clarification of the neuronal circuits in the brain that drive a behavior reaction dependent on ESP22. Future exciting news in the field of chemosensory will then depend on and result from their discovery.