American scientist who, with Linda B. Buck (Buck, Linda B.), won the Nobel Prize for Physiology or Medicine in 2004 for pioneering research on the olfactory system.

Axel received an A.B. (1967) from Columbia University and an M.D. (1970) from Johns Hopkins University School of Medicine. In 1978 he became a member of the pathology and biochemistry faculty at Columbia, where in the early 1980s Buck worked under him as a postdoctoral student. Axel joined the Howard Hughes Medical Institute (Hughes Medical Institute) (HHMI) as an investigator in 1984.

In 1991 Buck and Axel jointly published their seminal paper, based on research they had conducted with laboratory rats, that detailed their discovery of the family of 1,000 genes that encode, or produce, an equivalent number of olfactory receptors (olfactory receptor). Responsible for detecting the odorant molecules in the air, these receptors are located on olfactory receptor cells, which are clustered within a small area in the back of the nasal cavity. The two scientists then explained how the olfactory system works by showing that each receptor cell has only one type of odour receptor, which is specialized to recognize a limited number of odours. After odorant molecules bind to receptors, the receptor cells send electrical signals to the olfactory bulb in the brain. The brain combines information from several types of receptors in specific patterns, which are experienced as distinct odours.

Axel and Buck later determined that most of their findings concerning the sense of smell are virtually identical in rats, humans, and other animals, although they discovered that humans have only about 350 types of working olfactory receptors, about one-third the number in rats. The genes that encode olfactory receptors in humans account for about 3 percent of all human genes. Axel's HHMI laboratory also studied how sensory information is represented and sought to create a topographic map of olfactory representation in the brain.