Excerpts from citation for Medicine Nobel

Americans Axel and Buck have solved the enigmatic of the sense of smell, and in a series of pioneering studies clarified how our olfactory system works.

Excerpts from the citation awarding the 2004 Nobel Prize in Physiology or Medicine to Americans Richard Axel and Linda B Buck for their discoveries in the details of the sense of smell.

HT Image

The sense of smell has long remained the most enigmatic of our senses. The basic principles for recognizing and remembering about 10,000 different odors were not understood.

This year's Nobel Laureates in physiology or medicine have solved this problem and in a series of pioneering studies clarified how our olfactory system works. They discovered a large gene family, comprised of some 1,000 different genes (3 per cent of our genes) that give rise to an equivalent number of olfactory receptor types. These receptors are located on the olfactory receptor cells, which occupy a small area in the upper part of the nasal epithelium and detect the inhaled odorant molecules.

The conclusion that each olfactory receptor cell only expresses one single odorant receptor gene was highly unexpected. Axel and Buck continued by determining the organization of the first relay station in the brain. The olfactory receptor cell sends its nerve processes to the olfactory bulb, where there are some 2,000 well-defined microregions, glomeruli. There are thus about twice as many glomeruli as the types of olfactory receptor cells.

The general principles that Axel and Buck discovered for the olfactory system appears to apply also to other sensory systems. Pheromones are molecules that can influence different social behaviors, especially in animals. Axel and Buck, independent of each other, discovered that pheromones are detected by two other families of GPCR, localized to a different part of the nasal epithelium. The taste buds of the tongue have yet another family of GPCR, which is associated with the sense of taste.