Researchers from Northwestern University and Lund University collaborated on a study showing how catnip could protect itself from insects. They found that catnip had the same effect as chemical mosquito sprays like DEET. The article was published on March 4, 2021 in the magazine
Companies often add catnip to cat snacks and toys due to its euphoric and hallucinogenic effects on cats. However, people have also been using catnip for thousands of years to protect themselves from insects. Recent research found that catnip compounds they have the same effect on insects as synthetic insect repellants.
Researchers did not know what caused the insect repellency to catnip, a member of the mint family, until recently. In this study, the research teams found the mechanism behind mosquitoes’ aversion to the plant.
“Catnip and its active ingredient, nepetalactone, have been used for millennia to protect against insect pests, at least since the time of Pliny the Elder,” said Marcus C. Stensmyr, associate professor at Lund University and corresponding co-author. “But why catnip is so potent in such a wide range of insect species is unknown.”
The most common method of controlling mosquito populations is the use of insecticides. However, those do not target other species of insects. Synthetic insect repellants like DEET inhibit taste and smell receptors in mosquitoes so that they cannot recognize human prey. Catnip targets a different receptor in insects, but is just as effective in deterring them.
“We discovered that catnip and its active ingredient nepetalactone activate the irritant receptor TRPA1, an ancient pain receptor found in animals as diverse as flatworms, fruit flies and humans,” said Marco Gallio, associate professor of neurobiology at Weinberg College of the Arts. and Sciences. “We now believe that catnip is so aversive to so many species of insects because it activates this generalized irritant receptor.”
Catnip can play a crucial role in protecting against insect-borne diseases caused by climate change.
Previous studies by the Gallio Lab and others found a common receptor among humans, insects, and many other animal species. All three possess a type of transient receptor potential ion channel ankyrin 1 (TRPA1). This protein is commonly called the “wasabi receptor,” which detects environmental irritants such as pain and itching. However, catnip only seems to work on insects and animals like cats, but not humans.
“What’s particularly interesting is that, unlike wasabi or garlic compounds that also activate these receptors in humans, catnip appears to selectively activate the insect receptor,” Gallio said. “This explains why humans are indifferent to it and provides a great advantage for its use as a repellent.”
Researchers don’t know exactly why cats react so strongly to catnip. Some studies have suggested that catnip it affects the reward system in a cat’s brain, triggering the euphoric reaction. One of the active ingredients in catnip is believed to interact with a molecular component in this part of a cat’s brain.
The research team believes that the same plant that attracts cats could repel insects like mosquitoes. As the weather continues to warm, it will create the perfect conditions for disease-carrying insects like mosquitoes. Finding out how to smother the mosquito population with repellants is crucial to preventing the spread of disease.
“Mosquitoes, particularly those that act as vectors of disease, are becoming a bigger problem as climate change creates attractive conditions for them further north and south of the equator,” Stensmyr said. “Compounds derived from plants represent an emerging new approach to developing insect repellants, as plants have long known how to protect themselves from insect pests.”
Gallio says that plant repellants like catnip cost much less than synthetic chemicals. Also, more people have access to them. In developing countries where mosquito-borne diseases are rampant, catnip could make a big difference for these reasons.
The experiment that showed how catnip repels a variety of insect species
Gallio’s laboratory at Northwestern focuses primarily on studying the sensory systems of the common laboratory fruit fly Drosophila. They investigate what controls their responses to external temperature and pain. However, in Lund’s Stensmyr laboratory, researchers primarily study mosquitoes and other insect vectors of human disease.
Both teams of researchers studied different species of insects to understand why catnip repels insects but does not affect humans. The team conducted several tests, including administering food to the mosquitoes covered with a nylon sock soaked in catnip. They also conducted experiments that involved a wind tunnel and one in which the volunteers placed their hands inside a cage with mosquitoes. Some participants had their hands rubbed with catnip oil and the other group did not.
Gallio believes that the mechanism they found in the study provides evidence for the development of new insect repellants. He says these repellants will likely utilize knowledge of how to target mosquitoes’ irritant receptor. They will continue to study the mechanism behind how the Catnip affects this receptor in insects.
“This is an entry point to study how this molecule works in the receptor,” he said. “Once we understand its chemistry and how it interacts with the receptor, we could design even more powerful and selectively targeted molecules.”
Repellants that use catnip or other plant derivatives would also positively affect the environment. Since many people use repellants that contain DEET, it ends up in waterways and can adversely affect marine life. It can also cause a rash and irritation in some people with sensitive skin. Therefore, a plant-based product would not only help the environment, but also improve safety in humans.
Most people only think of catnip as the plant that makes cats “high” due to its hallucinogenic effect. However, researchers have found that this same plant can also repel mosquitoes. In fact, the study showed that it had the same effect as synthetic mosquito spray in protecting against insects.
The team discovered that catnip interacts with an insect receptor that detects environmental irritants, called TRPA1. Although catnip does not affect humans, this receptor is activated in insects exposed to it. In the future, perhaps catnip can replace all synthetic sprays, which will have a small positive impact on the environment.