Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Researchers Record First "Pheromone Images" in Brains of Mice

14.02.2003


Howard Hughes Medical Institute researchers are beginning to unravel how a mysterious sixth sense guides animal attraction. The scientists have made the first-ever recordings of patterns of brain activity in a mouse as it explores the sex and identity of a newly encountered animal.

The research team, led by Lawrence C. Katz, a Howard Hughes Medical Institute investigator at Duke University Medical Center, recorded the firing of neurons in the accessory olfactory bulb, part of a poorly understood sensory pathway that is thought to be important in sex discrimination and social behavior in most mammals. Katz presented his research findings at the annual meeting of the American Association for the Advancement of Science in Denver, Colorado.

The results of the studies, which will also be published in a future issue of the journal Science, show that chemical signals called pheromones trigger highly specific patterns of neural excitation in the brain. These “pheromone images” provide vital information about the sexual receptiveness of females and the dominance hierarchy in males, among other things, said Katz.



“Mice, which live in the darkness in the wild, can readily identify each other on the basis of a pheromonal image rather than a visual image,” said Katz.

Both wild and domestic animals, such as dogs and cats, collect pheromone signals through the “flehmen” response, in which the upper lip curls back during exploration of the oral and anogenital areas of other animals during social encounters. These pheromone signals are collected by the vomeronasal organ (VNO), a hollow tube in the nasal cavity. Sensory neurons lining the VNO, in turn, stimulate neurons in the accessory olfactory bulb, a part of the central nervous system. Finally, signals are sent to the amygdala, a part of the brain responsible for basic drives, such as fear, aggression, mating behavior and maternal instincts.

The information contained in pheromone signals is key to survival and reproduction, said Katz. Male mice establish dominance hierarchies, so they need to know if another male is dominant or non-dominant. In addition, males respond to females who are in estrus because they smell differently. “In essence,” said Katz, “these pheromonal cues help mice decide `should I mate or fight.’”

Important clues to the VNO’s importance in sex recognition have emerged from genetic studies. For example, HHMI investigator Catherine Dulac and her colleagues at Harvard University reported in January 2002 that mice lacking a key molecule in the pheromone-signaling pathway were unable to distinguish males from females and behaved as if all mice were female.

To capture the pheromonal image created by this accessory olfactory system, Katz and his colleagues, which included Minmin Luo of Duke and Michale Fee of Lucent Technologies in Murray Hill, N.J., developed miniature electrodes and micromotors to record the firing of individual neurons in mice that were awake and behaving normally. The electrodes were implanted in the accessory olfactory bulb, which along with the main olfactory system, processes pheromone signals. The micromotors, which are about the size and shape of a pencil eraser, were light and unobtrusive, so they did not interfere with the normal activities of the mice, said Katz. Once the recording device was attached to the mouse, the researchers introduced another mouse into the cage and allowed the two to interact. In each case, test animals repeatedly explored the faces and anogenital areas of the stimulus animals with their snouts.

The scientists then recorded male mouse responses to females, males of the same and different genetic backgrounds, and castrated males. To be certain they were recording responses to pheromones, the scientists also recorded responses as the test mice investigated fake mice, which never evoked any neuronal response.

“No one has ever recorded from this area because it only works while the animals are awake and exploring their environment,” said Katz. “What we’ve done is look at how that sensory information is sent into a central location and what kind of information is represented in the brain.”

When they began their studies, the scientists hypothesized that individual neurons might be responsible for detecting “maleness” or “femaleness,” but instead they found a much more sophisticated sensory system that could distinguish individuals with great fidelity.

“The most exciting thing we found was that individual neurons were responsive to individual animals. Each type of animal encountered set off a unique pattern of neural excitation or inhibition,” said Katz. “We did not see any neurons that responded to all male mice or to all female mice. They responded to the male mice of a specific genetic identity, but not to male mice of other genetic backgrounds. This suggests there must be pheromones that male mice of one genetic identity have, but that male mice of another genetic identity do not. In essence, each individual animal has a different pheromonal signature.”

“What we also learned,” he added, “is that there must be pheromonal signals, whose identity we do not yet know, that carry information about sexual identity.”

There is evidence that humans also respond to pheromone signals, said Katz. “Don’t forget that for years the main ingredient in perfume was a secretion from the anal gland of the civet cat, which is probably full of pheromones. In addition, there is evidence in humans that pheromone-like molecules activate different parts of the brain than standard odorants. And a lot of people think that kissing and all of the other oral investigations that humans engage in is a vestige or even an ongoing part of this pheromone system.”

Jim Keeley | Howard Hughes Medical Institute
Further information:
http://www.hhmi.org/news/katz2.html

More articles from Life Sciences:

nachricht Cancer diagnosis: no more needles?
25.05.2018 | Christian-Albrechts-Universität zu Kiel

nachricht Less is more? Gene switch for healthy aging found
25.05.2018 | Leibniz-Institut für Alternsforschung - Fritz-Lipmann-Institut e.V. (FLI)

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Powerful IT security for the car of the future – research alliance develops new approaches

The more electronics steer, accelerate and brake cars, the more important it is to protect them against cyber-attacks. That is why 15 partners from industry and academia will work together over the next three years on new approaches to IT security in self-driving cars. The joint project goes by the name Security For Connected, Autonomous Cars (SecForCARs) and has funding of €7.2 million from the German Federal Ministry of Education and Research. Infineon is leading the project.

Vehicles already offer diverse communication interfaces and more and more automated functions, such as distance and lane-keeping assist systems. At the same...

Im Focus: Molecular switch will facilitate the development of pioneering electro-optical devices

A research team led by physicists at the Technical University of Munich (TUM) has developed molecular nanoswitches that can be toggled between two structurally different states using an applied voltage. They can serve as the basis for a pioneering class of devices that could replace silicon-based components with organic molecules.

The development of new electronic technologies drives the incessant reduction of functional component sizes. In the context of an international collaborative...

Im Focus: LZH showcases laser material processing of tomorrow at the LASYS 2018

At the LASYS 2018, from June 5th to 7th, the Laser Zentrum Hannover e.V. (LZH) will be showcasing processes for the laser material processing of tomorrow in hall 4 at stand 4E75. With blown bomb shells the LZH will present first results of a research project on civil security.

At this year's LASYS, the LZH will exhibit light-based processes such as cutting, welding, ablation and structuring as well as additive manufacturing for...

Im Focus: Self-illuminating pixels for a new display generation

There are videos on the internet that can make one marvel at technology. For example, a smartphone is casually bent around the arm or a thin-film display is rolled in all directions and with almost every diameter. From the user's point of view, this looks fantastic. From a professional point of view, however, the question arises: Is that already possible?

At Display Week 2018, scientists from the Fraunhofer Institute for Applied Polymer Research IAP will be demonstrating today’s technological possibilities and...

Im Focus: Explanation for puzzling quantum oscillations has been found

So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics

Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

In focus: Climate adapted plants

25.05.2018 | Event News

Save the date: Forum European Neuroscience – 07-11 July 2018 in Berlin, Germany

02.05.2018 | Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

 
Latest News

In focus: Climate adapted plants

25.05.2018 | Event News

Flow probes from the 3D printer

25.05.2018 | Machine Engineering

Less is more? Gene switch for healthy aging found

25.05.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>