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 Newly discovered bacteria-binding protein in the intestine
08.12.2016 | University of Gothenburg

nachricht The balancing act: An enzyme that links endocytosis to membrane recycling
07.12.2016 | National Centre for Biological Sciences

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Scientists track chemical and structural evolution of catalytic nanoparticles in 3-D

08.12.2016 | Materials Sciences

Decoding cement's shape promises greener concrete

08.12.2016 | Materials Sciences

Will Earth still exist 5 billion years from now?

08.12.2016 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>