"The ability to desensitize to odors is important for our well-being," says Randall Reed, Ph.D., a Howard Hughes Medical Institute (HHMI) investigator and a molecular biologist and neuroscientist in the school's Institute for Basic Biomedical Sciences. "Odor adaptation is important in telling whether a scent is getting stronger or going away, and it prevents sensory overload. Understanding this process should help us figure out how adaptation affects our perception of odors."

Two papers published in the Dec. 8 issue of Science show that a protein called CNGA4 helps plug the "nose" of odor receptor cells -- neurons whose job is to detect smells and send that information to the brain as an electrical signal. The "nose" is really a channel in the neurons' membrane that opens when an odor is presented and closes as the neuron becomes desensitized to that smell.

By measuring the signals from these odor receptor cells in genetically engineered mice, Reed and his colleagues showed that mice lacking CNGA4 can't adapt to odors. Other scientists studied the molecule's behavior in laboratory-grown cells and reported that CNGA4 speeds up the "nose's" closing.

In normal mice, and in humans, the electrical signal from odor receptor neurons diminishes quickly over time, even when the odor is still present. Also, the neurons usually produce a much smaller electrical signal if exposed to the same odor twice in a short period of time, says Reed.

Using mice that were missing CNGA4, a protein they thought to be involved in odor sensitivity, Reed and his collaborators from the University of Maryland, Baltimore, found that mice without CNGA4 could sense odors but could not adapt to them. In these mice, the signal from the neurons st
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Contact: Joanna Downer
jdowner1@jhmi.edu
410-614-5105
Johns Hopkins Medical Institutions
4-Feb-2002