Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Olfactory nerve cells expressing same receptor display a varied set of reactions


Findings help researchers revise models of mammalian sense of smell

Composite of olfactory neuron response to lyral odor. The background shows intact olfactory neuroepithelium containing MOR23 cells tagged with GFP (green fluorescent protein). The right upper corner shows dendritic knob and cilia from a single MOR23 neuron. The left lower corner shows the electrical responses over time of a single MOR23 cell to lyral, the ligand for MOR23, at different concentrations. (Credit: Xavier Grosmaitre and Minghong Ma, PhD, University of Pennsylvania School of Medicine)

In a mouse model, University of Pennsylvania School of Medicine researchers discovered that olfactory sensory neurons expressing the same receptor responded to a specific odor with an array of speeds and sensitivities, a phenomenon previously not detected in the mammalian sense of smell. The group published their findings this week in the online edition of the Proceedings of the National Academy of Sciences.

"We assumed that the sensory neurons that express the same receptor would respond to a specific odor in the same way," says senior author Minghong Ma, PhD, Assistant Professor of Neuroscience at Penn. "But in real biology, these olfactory neurons keep regenerating, and even though they all express the same receptor, they’re probably at different states of maturation, displaying different qualities. By knowing that olfactory neurons can respond differently, we’re adding another layer to understanding how the olfactory system receives outside information."

Ma’s group measured 53 different olfactory neurons that express the MOR23 odor receptor. As a group, the neurons reacted differently from one another in their response to lyral, an artificial odor used in fragrances and flavoring. After subjecting all cells to a short pulse (200-300 milliseconds) of lyral, the researchers measured the cells’ sensitivity to the odor. Some cells responded to very low concentrations of lyral; others, to higher concentrations. Regarding the cells’ reaction time, some neurons finished firing within 500 milliseconds, but for others, the response time was up to five seconds.

Detection of odor molecules depends on about 1000 different odor receptors in the rodent nose. Different sets of receptors respond to different sets of odors. To date, no one has been able to record electrical impulses from a specific subtype of olfactory sensory neuron expressing a known receptor. This is important, says Ma, because prior to this paper, when researchers would work with olfactory cells, there was no way to know what odor receptor that cell expressed. "It could literally be one out of 1000," she says.

All the sensory neurons expressing the same receptor merge to a common region called a glomerulus, a region in the brain’s olfactory bulb. In one bulb there are about 2000 glomeruli. (The brain has two olfactory bulbs.) There are thousands of sensory neurons dedicated to expressing the same receptor, and in the case of MOR23 they all merge to two glomeruli.

The researchers used genetically engineered mice that express MOR23 together with green fluorescent protein (GFP), which was generated by colleagues from Rockefeller University. The GFP allows the investigators to visualize the MOR23 cells separate from other neurons. They also recorded their measurements using cells still intact within the lining of the nose, which allows the researchers to study these cells in their natural biochemical environment.

The researchers made their measurements from the endings of olfactory neuron dendrites. A single dendrite extends from the cell body of the olfactory neuron into the nasal cavity. The dendrite has a swelling at the end called the knob, where about 10 to 15 hair-like extensions called cilia contain the odor receptors.

Ma and colleagues are now working out the implications of their findings. She says this study points to a more finely tuned response in the brain to odors than previously thought. "Olfactory neurons may be able to respond to an even wider range of odor concentrations than we realized," she says. The heterogeneity in odor sensitivity and the wide response range in single cells provides new insights into why mammals, including humans, perceive odors with unchanged quality over a broad concentration range.

Karen Kreeger | EurekAlert!
Further information:

More articles from Studies and Analyses:

nachricht Rutgers-led innovation could spur faster, cheaper, nano-based manufacturing
14.02.2018 | Rutgers University

nachricht New study from the University of Halle: How climate change alters plant growth
12.01.2018 | Martin-Luther-Universität Halle-Wittenberg

All articles from Studies and Analyses >>>

The most recent press releases about innovation >>>

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

Im Focus: Tiny implants for cells are functional in vivo

For the first time, an interdisciplinary team from the University of Basel has succeeded in integrating artificial organelles into the cells of live zebrafish embryos. This innovative approach using artificial organelles as cellular implants offers new potential in treating a range of diseases, as the authors report in an article published in Nature Communications.

In the cells of higher organisms, organelles such as the nucleus or mitochondria perform a range of complex functions necessary for life. In the networks of...

Im Focus: Locomotion control with photopigments

Researchers from Göttingen University discover additional function of opsins

Animal photoreceptors capture light with photopigments. Researchers from the University of Göttingen have now discovered that these photopigments fulfill an...

Im Focus: Surveying the Arctic: Tracking down carbon particles

Researchers embark on aerial campaign over Northeast Greenland

On 15 March, the AWI research aeroplane Polar 5 will depart for Greenland. Concentrating on the furthest northeast region of the island, an international team...

Im Focus: Unique Insights into the Antarctic Ice Shelf System

Data collected on ocean-ice interactions in the little-researched regions of the far south

The world’s second-largest ice shelf was the destination for a Polarstern expedition that ended in Punta Arenas, Chile on 14th March 2018. Oceanographers from...

Im Focus: ILA 2018: Laser alternative to hexavalent chromium coating

At the 2018 ILA Berlin Air Show from April 25–29, the Fraunhofer Institute for Laser Technology ILT is showcasing extreme high-speed Laser Material Deposition (EHLA): A video documents how for metal components that are highly loaded, EHLA has already proved itself as an alternative to hard chrome plating, which is now allowed only under special conditions.

When the EU restricted the use of hexavalent chromium compounds to special applications requiring authorization, the move prompted a rethink in the surface...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

Virtual reality conference comes to Reutlingen

19.03.2018 | Event News

Ultrafast Wireless and Chip Design at the DATE Conference in Dresden

16.03.2018 | Event News

International Tinnitus Conference of the Tinnitus Research Initiative in Regensburg

13.03.2018 | Event News

Latest News

Thawing permafrost produces more methane than expected

20.03.2018 | Earth Sciences

Scientists invented method of catching bacteria with 'photonic hook'

20.03.2018 | Physics and Astronomy

Next Generation Cryptography

20.03.2018 | Information Technology

Science & Research
Overview of more VideoLinks >>>