The world is spinning before our eyes. Sweat breaks out all over the body. One wrong move can cause us to start chugging.
Frailty can be caused by anything from a car ride to chemotherapy. For some, it is only a passing ailment, while others suffer from chronic nausea that affects their entire daily life and impairs their quality of life.
Apart from the discomfort itself, nausea can also lead to fatigue and lack of energy, which can lead to weight loss. The stomach acid produced by frequent vomiting can damage both the esophagus and the teeth.
Despite how common nausea is and how serious its consequences can be, very little has been known about its medical causes until now.
Scientists have now for the first time managed to find out the root of nausea in the brain and are now working hard to use this breakthrough information to cure this unpleasant ailment.
Anything possible can cause success
Nausea is not considered a disease in itself, but rather a series of symptoms that can manifest themselves for many reasons. The symptoms are often dizziness, discomfort and stomach ache, loss of appetite, sweating, involuntary contraction of the muscles around the internal organs and when the worst happens – vomiting.
Some people don’t actually throw up and it can be even more uncomfortable. The reason for this is that our brains produce so-called endorphins when we are done throwing up. Endorphins are substances that produce feelings of well-being and happiness, and as a result, there may be a convenient solution to the vomiting itself. Without vomiting, this sedative effect of the endorphins is missing.
A number of different factors can trigger nausea, and since each of these factors has a different effect on the body, the source of nausea is not always the same.
Motion sickness and dizziness, for example, affect the brain in that both cause disturbances in the optic nerve and the sense of balance, but on the other hand, overeating can cause nausea by affecting the stomach’s tensor sensors.
It is not known for sure why the body responds to these effects by inducing nausea. In some cases, however, the feeling is a good thing. By inducing vomiting, nausea caused, for example, by the consumption of alcoholic beverages or spoiled food can benefit the body to reduce the effects of the damage. When we vomit, we get rid of toxins from the stomach before they enter the bloodstream.
This bodily function is probably also the reason why some types of drugs, including cancer drugs and diabetes drugs, can cause fatigue, because the body simply perceives the drugs as toxins that need to be removed.
The various causes of nausea are precisely why scientists have struggled to find the root of the discomfort. However, they have long suspected certain areas of the brain.
The brain makes us throw up
As early as the 1960s, researchers discovered that a brain region called the Area postrema in the spinal cord was somehow connected to nausea. In the 1990s, it was experimentally demonstrated that electrical stimulation of this area in question resulted in wandering symptoms in mice. However, damage to this same region rendered the mice unable to sense nausea.
Today, scientists know that the area postrema triggers nausea when the area detects certain toxins or hormones from the blood. The area is responsible for, among other things, nausea of pregnancy, hangovers and nausea associated with taking certain drugs, but not motion sickness, which seems to have its roots in other areas of the brain.
The brain region’s ability to respond to the chemicals in the blood is related to its location. The area is found in the so-called fourth cerebral cavity of the brainstem and is therefore outside the part of the brain where the blood vessels are surrounded by blood-brain barriers. These restrictions keep substances from the brain cells that can be thought to be harmful, but the substances can still enter the area postrema.
In the brain area, the chemicals activate an area called the CTZ (chemoreceptor trigger zone), which contains many receptors that are sensitive to the chemicals. CTZ then sends signals to other parts of the brain and body that trigger nausea and vomiting.
Several types of anti-nausea drugs work by blocking the receptors in CTZ. The problem is that there are many different receptors and the drugs do not always hit the receptor that causes the nausea. The receptors are also found elsewhere in the body, where they play an important role that has nothing to do with nausea, and as a result, the drugs can have unfortunate side effects.
For taste, there is an urgent need for new types of drugs. Scientists have discovered a previously unknown aspect of the biology of nausea that can be crucial in the fight against the disease.
New technology reveals an important detail
The nausea area area postrema is extremely small and the furthest part of the brain, which makes it difficult to study the area. In 2021 , a team of researchers at Harvard Medical School managed to uncover a little of everything related to this small area of neurons, thanks to a new revolutionary method.
Scientists managed to very carefully remove the brain region from mice and then studied it with the help of a technique known in English as single-core RNA sequencing, i.e. reading of RNA from a single cell nucleus.
RNA is a type of copy of the active genetic code in the cell nucleus and serves as instructions for the cell’s proteins. By reading RNA, scientists can find out what proteins the cell makes.
The proteins are a kind of workers of the cell, and the composition of proteins reveals what properties the cell has and what it is capable of.
The study revealed that the area postrema contains two very different types of neurons.
The second group of cells triggers the nausea, but the second group is able to suppress the first and prevent the discomfort.
The discovery made the Harvard scientists decide to launch a new study in 2022, this time with a drug that seems to have several advantages.
New drugs on the way
The scientists first instead fed a group of lab mice water to which a nausea-inducing substance had been added. The discomfort caused the mice to avoid the water.
Another group of mice was given water containing the same substance but to which the hormone GIP had also been added. This hormone activates the neurons that suppress the feeling of nausea.
The experiment was successful. GIP overcame the effects of the nauseating agent in the water, and the mice drank the water to their heart’s content without feeling nauseous.
The results are promising and pave the way for a brand new method in the fight against nausea. In the past, researchers primarily relied on drugs that inhibited specific receptors on the neurons that activate nausea. Each individual receptor is only involved in a few types of nausea, and for the taste the drugs do not help many patients at all.
However, by activating the neurons that suppress nausea, the doctors only need one unique drug against all kinds of ailments, from hangovers and morning sickness in pregnant women to nausea caused by cancer drugs.
The only type of success that this new weapon of the researchers at Harvard does not seem to overcome is motion sickness. However, this method, which consists of studying the exact individual neurons of the brain, will hopefully also reveal the mystery of motion sickness and reveal how the various types of nausea are connected in the brain.
When this happens, scientists will finally succeed in developing a universal drug that should benefit everyone, from cancer patients to car sickness.
