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 A Map of the Cell’s Power Station
18.08.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau

nachricht On the way to developing a new active ingredient against chronic infections
18.08.2017 | Deutsches Zentrum für Infektionsforschung

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

A Map of the Cell’s Power Station

18.08.2017 | Life Sciences

Engineering team images tiny quasicrystals as they form

18.08.2017 | Physics and Astronomy

Researchers printed graphene-like materials with inkjet

18.08.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>