New collaborative research from the North-West University and the University of Lund could turn people to their backyard at the beginning of this year’s mosquito season instead of to the store.
It is often used as an additive for cat toys and treats due to the euphoric and hallucinogenic effects on cats, and catnip has also long been known for its powerful repellent on insects, especially mosquitoes. Recent research shows that catnip compounds are at least as effective as synthetic insecticides such as DEET.
But until now, the mechanism that caused insects’ aversion to this common member of the mint family was unknown. In a paper published in the magazine on March 4 Current biology, reports a team of researchers from North-West and Lund universities to find the underlying receptors that contribute to the aversion to mosquitoes.
“Catnip and its active ingredient, Nepetalactone, have been used for millennia to ward off insect pests, at least since the time of Pliny the Elder,” said Marcus C. Stensmyr, associate professor at Lund University and co-author, said. “But why Catnip is so strong for such a wide variety of insect species has remained unknown.”
Traditional approaches to mosquito control have involved insecticides, but other insect species are eliminated as collateral damage. Modern formulations of insecticides such as DEET target mosquito odor and taste receptors, which do not enable the insect to recognize the chemical indications that a human prey indicates.
“We have discovered that Catnip and the active ingredient Nepetalactone activate the irritating 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 Arts and Arts. , said. Sciences. “We now think that Catnip is so frightening to so many insect species because it activates this widespread irritating receptor.”
In previous work, the Gallio Lab and others have shown that humans, insects and many other animal species have a version of the transient receptor potential ankyrin 1 (TRPA1) ion channel, a protein known in particular as the “wasabi receptor” which irritating environmental irritants such as pain and itching.
“What is particularly interesting is that, unlike wasabi or garlic compounds, which also activate these receptors in humans, the catnip appears to selectively activate the insect receptor,” Gallio said. “It explains why people are indifferent to it, and offers a serious benefit to its use as a repellent.”
The reason why cats feel so attracted to catnip is a very different story that is not completely understood. Research suggests that this may be due to an unusual interaction between one of the active ingredients of catnip and a molecular component found in the reward system of the feline brain.
“Mosquitoes, especially those that act as vectors for diseases, are becoming a bigger problem as climate change creates attractive conditions for them north and south of the equator,” Stensmyr said. “Plant compounds represent a new emerging approach to the development of insecticides, as plants have long known how to protect themselves from insect pests.”
Gallio added that plant repellents are often available at a much lower cost and are more readily available. The accessibility of Catnip can have major consequences in developing countries where mosquito-borne diseases are a major problem.
The Gallio Laboratory in the Northwest is studying the sensory systems of the common Lab fruit fly Drosophila, including the mechanisms that control responses to external temperature and pain. Lund’s Stensmyr laboratory focuses mainly on mosquitoes and other insect vectors of human diseases.
The researchers studied different insect species to better understand how catnip and its active ingredient work to ward off a wide variety of insects while having no irritating effect on humans.
To confirm their results, the team conducted a series of tests, including mosquitoes offering a blood meal in a dish covered with a nylon sock dipped in catnip, experiments with a wind tunnel and experiments in which volunteers put their hand in a cage farm with live mosquitoes, with or without the protection of a catnip oil rub.
Gallio believes that the mechanism they are discovering also provides evidence of the development of the next generation of repellents that use the same logic – selectively focusing on the mosquito-irritating receptor.
“This is a starting point to investigate how this molecule works on the receptor,” he said. “Once we understand its chemistry and how it interacts with the receptor, we can design even more powerful and selectively directed molecules.”
The team’s next project? Discover how to get rid of the cats that keep chasing them.