Nose receptors adapt to surrounding smells, researchers find

Feb. 26 (UPI) -- New research suggests the nose adapts to the environment, changing to relay information to the brain about the most common surrounding smells as efficiently as possible.

The findings -- published this week in the journal eLife -- could offer new insights into how the mammalian nose and olfactory system evolved, as well as how the system is impacted by the aging process.

The nose of a mouse contains some 10 million receptor neurons. These cells are organized into 1,000 types, and each type specializes in receiving certain kinds of molecules. Different types of neurons are activated by a variety of molecules, and different smells activate an array of neurons. As a result, the brain must process activation patterns, or signatures, across the full spectrum of receptor types.

"Some types of receptor neurons in the nose are used more often than others, depending on the animal's species," Tiberiu Tesileanu, a computational biologists at the Flatiron Institute in New York, said in a news release. "Recent experiments have also shown that the way different receptor types are used can change when animals are exposed to different smells. In our current study, we set out to explain these findings and build a model that can predict the observed biases in how receptors are used."

Researchers in the United States and France modeled the distribution of receptor types, using the assumption that the nose and its many neurons are adaptable. An adaptable nose benefits from a larger number of neuron types that are activated by a variety of common smells.

"The receptor types activated by variable smells are important because they convey a lot of information to the brain about this variability, and are more abundant in the nose because of this," Tesileanu said. "To our knowledge, this is the first time that such 'efficient coding' ideas have been applied to explain patterns in the use of receptor neurons by the nose."

Researchers based their assumption on the results of experiments that measure the effects of different aromas on the organization of receptor neurons in mice.

"Experimentally, increased exposure to odorants leads variously, but reproducibly, to increased, decreased, or unchanged abundances of different activated receptors," researchers wrote in their new paper.

Using their experimental data and new model, scientists developed an algorithm to predict how different environments influence the organization of receptor neuron types in the nose.

"Comparing the results of these experiments to the changes predicted by our model would provide a strong test of how well these neurons take information to the brain when they first detect a new smell," said Vijay Balasubramanian, researcher at the University of Pennsylvania.