Baby's tears and mom's libido

October 26, 2018

A substance in young mice's tears makes female mice more likely to reject male sexual advances. This research is part of ongoing efforts at the University of Tokyo to understand how animals communicate using chemicals called pheromones.

Direct connections between human and mouse behavior cannot be made because pheromones are highly species specific.

"If humans can detect anything in tears, we won't use the same pheromone signal or receptor as mice. But we are investigating if species share the basic neurocircuitry of how the brain processes an olfactory signal to affect behavior," said Professor Kazushige Touhara, leader of the research project.

Pheromone population control

Researchers hope to use the tear pheromone as a natural mouse birth control to reduce mouse populations in the future.

"It is unlikely that other animals would be affected because pheromones are so species specific. The sex-rejecting behavior is an innate instinct, so it's also unlikely that the mice will learn to change their behavior or ignore the artificial pheromone," said Touhara.

Only juvenile mice aged one to three weeks produce the pheromone, called exocrine gland-secreting peptide 22 (ESP22). ESP22 is not airborne and lacks a noticeable odor, but the pheromone spreads around the territory as mothers and young mice wipe tears while grooming.

Both mothers and virgin female mice reject male sexual advances after exposure to ESP22. Less female interest in sex would theoretically benefit juvenile mice by reducing the number of younger siblings competing for resources.

"ESP22 is difficult to artificially synthesize, so we want to find a smaller portion of the pheromone molecule that could be added to mouse drinking water. This could prevent mice breeding in areas where they are pests," said Touhara.

Specific receptors

ESP1 is an adult male pheromone that Touhara's research group has previously studied for its role in enhancing female acceptance of sex. In this new study, researchers tracked how ESP22 and ESP1 are received and processed by the adult female mouse brain.

Pheromone signals from young mice overrode the signals from adult males. Virgin female mice rejected male advances when they were exposed to the sex-rejecting ESP22 even after being exposed to the sex-accepting ESP1.

Both sex-rejecting ESP22 and sex-accepting ESP1 pheromones are recognized by single, dedicated receptors in the nose. Specific neurons send the different pheromone signals to the brain. The presence of similar but specific ESP1 and ESP22 receptors helps reveal how animals evolved the ability to detect and interpret pheromone signals.

"The discovery of only one receptor for each pheromone shows us that single molecules can drastically affect animal behavior," said Touhara.

Pheromones in the brain

Pheromone signals are routed to the medial amygdala, a small group of neurons in the brain.

"The medial amygdala is like a hub to receive and reroute pheromone signals," said Kentaro Ishii, a co-first author of the research paper and fifth-year doctoral student working with Touhara.

ESP22 and ESP1 signals travel separately but in parallel until reaching the medial amygdala. After that point, the pheromones affect different neurocircuitry in the brain to create different behaviors. Ongoing research in the laboratory will explore pheromone-related neurocircuitry beyond the medial amygdala hub.

"The medial amygdala is still very mysterious, so we are excited to discover more details about how pheromone signals are sorted and routed after they are received there," said Ishii.

"Additionally, we want to understand the complexity of how the brain computes and sorts olfactory signals in a natural environment, where animals are simultaneously exposed to many different pheromones and other chemical signals all the time," said Ishii.
-end-
The paper is published by Nature Communications. Collaborators at RIKEN Center for Brain Science in Japan and Harvard Medical School in the U.S. also contributed to the research.

Journal Article

Takuya Osakada, Kentaro K. Ishii, Hiromi Mori, Ryo Eguchi, David M. Ferrero, Yoshihiro Yoshihara, Stephen D. Liberles, Kazunari Miyamichi, and Kazushige Touhara. 2018. Sexual rejection via a vomeronasal receptor-triggered limbic circuit. Nature Communications. DOI: 10.1038/s41467-018-07003-5.

Related Links

Graduate School of Agricultural and Life Sciences, The University of Tokyo website: http://www.a.u-tokyo.ac.jp/english/index.html

Kazushige Touhara website: http://park.itc.u-tokyo.ac.jp/biological-chemistry/profile_english/index.html

Research Contact

Professor Kazushige Touhara
Laboratory of Biological Chemistry, Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657
Tel: +81-(0)3-5841-5109
E-mail: ktouhara@mail.ecc.u-tokyo.ac.jp

Press Contacts

Ms. Caitlin Devor
Division for Strategic Public Relations, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654, JAPAN
Tel: +81-3-5841-0876
Email: press-releases.adm@mail.u-tokyo.ac.jp

About the University of Tokyo

The University of Tokyo is Japan's leading university and one of the world's top research universities. The vast research output of some 6,000 researchers is published in the world's top journals across the arts and sciences. Our vibrant student body of around 15,000 undergraduate and 15,000 graduate students includes over 2,000 international students. Find out more at http://www.u-tokyo.ac.jp/en/ or follow us on Twitter at @UTokyo_News_en.

University of Tokyo

Related Brain Articles from Brightsurf:

Glioblastoma nanomedicine crosses into brain in mice, eradicates recurring brain cancer
A new synthetic protein nanoparticle capable of slipping past the nearly impermeable blood-brain barrier in mice could deliver cancer-killing drugs directly to malignant brain tumors, new research from the University of Michigan shows.

Children with asymptomatic brain bleeds as newborns show normal brain development at age 2
A study by UNC researchers finds that neurodevelopmental scores and gray matter volumes at age two years did not differ between children who had MRI-confirmed asymptomatic subdural hemorrhages when they were neonates, compared to children with no history of subdural hemorrhage.

New model of human brain 'conversations' could inform research on brain disease, cognition
A team of Indiana University neuroscientists has built a new model of human brain networks that sheds light on how the brain functions.

Human brain size gene triggers bigger brain in monkeys
Dresden and Japanese researchers show that a human-specific gene causes a larger neocortex in the common marmoset, a non-human primate.

Unique insight into development of the human brain: Model of the early embryonic brain
Stem cell researchers from the University of Copenhagen have designed a model of an early embryonic brain.

An optical brain-to-brain interface supports information exchange for locomotion control
Chinese researchers established an optical BtBI that supports rapid information transmission for precise locomotion control, thus providing a proof-of-principle demonstration of fast BtBI for real-time behavioral control.

Transplanting human nerve cells into a mouse brain reveals how they wire into brain circuits
A team of researchers led by Pierre Vanderhaeghen and Vincent Bonin (VIB-KU Leuven, Université libre de Bruxelles and NERF) showed how human nerve cells can develop at their own pace, and form highly precise connections with the surrounding mouse brain cells.

Brain scans reveal how the human brain compensates when one hemisphere is removed
Researchers studying six adults who had one of their brain hemispheres removed during childhood to reduce epileptic seizures found that the remaining half of the brain formed unusually strong connections between different functional brain networks, which potentially help the body to function as if the brain were intact.

Alcohol byproduct contributes to brain chemistry changes in specific brain regions
Study of mouse models provides clear implications for new targets to treat alcohol use disorder and fetal alcohol syndrome.

Scientists predict the areas of the brain to stimulate transitions between different brain states
Using a computer model of the brain, Gustavo Deco, director of the Center for Brain and Cognition, and Josephine Cruzat, a member of his team, together with a group of international collaborators, have developed an innovative method published in Proceedings of the National Academy of Sciences on Sept.

Read More: Brain News and Brain Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.