Our sense of smell is one of the oldest of our senses yet the least understood. Two American scientists, Linda B. Buck and Richard Axel, discovered how people can smell and recall about 10,000 different odors in the early 1990’s. They were awarded the 2004 Nobel Prize. Their work provides a science based understanding of how people who smell a lilac for example in childhood can recognize the fragrance later in life, and also recall associated memories. Once inhaled, fragrant molecules start a process by which olfactory cells send messages to the olfactory bulb, a part of the brain that is associated with smell. The information is then relayed to other parts of the brain. They also discovered a large gene family that gives rise to the olfactory receptors located on cells in a small area in the upper part of the nose.
Well since then continued research has been conducted to further understand these receptors. It has been discovered that odor receptors are not just found in the nose but throughout the body.
A team of biologists at Ruhr University Bochum in Germany has found that our skin contains olfactory receptors. “More than 15 of the olfactory receptors that exist in the nose are also found in human skin cells,” said the lead researcher, Dr. Hanns Hatt. The presence of scent receptors outside the nose seems remarkable but as Dr. Hatt and others have observed, odor receptors are among the most evolutionarily ancient chemical sensors in the body, capable of detecting a multitude of compounds, not solely those drifting through the air.
“If you think of olfactory receptors as specialized chemical detectors, instead of as receptors in your nose that detect smell, then it makes a lot of sense for them to be in other places,” said Jennifer Pluznick, an assistant professor of physiology at Johns Hopkins University.
Dr. Hatt and his colleagues reported finding olfactory receptors inside the testes that function like a chemical guidance system helping sperm cells to find their way toward an unfertilized egg. Olfactory receptors have been found in the liver, heart, kidneys, colon, lungs and brain – and they are suggesting that almost every organ in the body contains olfactory receptors.
Olfactory receptors are the largest subset of G protein-coupled receptors, a family of proteins, found on the surface of cells, that allow the cells to sense what is going on around them. Interestingly, 40% of all prescription drugs target these G protein coupled-receptors. Humans have approximately 350 different olfactory receptors. What begins to make things more complicated is that many scent molecules may activate the same receptor and multiple receptors often react to the same scent.
We refer to these receptors as “olfactory” receptors because they were first discovered in the nose. Yehuda Ben-Shahar, a biologist at Washington University in St. Louis published a paper this year on olfactory receptors in the human lung, which he found act as a safety switch against poisonous compounds by causing the airways to constrict when we inhale noxious substances. “It’s an open question,” he said, “as to which evolved first.”
What will be interesting to follow now is just how “scent based medicine” in the “traditional realm” will be explored, developed used and/or abused. As aromatherapists we have always known the benefits of inhalation and topical application of essential oils and carriers. Can these new findings open up new doors for us to explore as well? Or does knowing that almost all the organs of our body have olfactory receptors confirm that our work is even more profound then most of us in the field even imagine?
What are your thoughts?
Information for this blog post was gathered from several NY Times Science articles.