Could catnip become the new insect repellant? – ScienceDaily

Often used as an additive for cat toys and treats due to its euphoric and hallucinogenic effects on cats, catnip has also long been known for its potent repellent action on insects, especially mosquitoes. Recent research shows that catnip compounds are at least as effective as synthetic insect repellents such as DEET.

But until now, the mechanism that triggered insect aversion to this common member of the mint family was unknown. In an article to be published on March 4 in the journal Current biology, a team of researchers from Northwestern and Lund Universities report finding the underlying receptors that contribute to the aversive response of mosquitoes.

“Catnip and its active ingredient, nepetalactone, have been used for millennia to ward off insect pests, at least since the days of Pliny the Elder,” said Marcus C. Stensmyr, associate professor at the Lund University and corresponding co-author. “But why catnip is so potent on such a wide range of insect species remains unknown.”

Traditional approaches to mosquito control involved insecticides, but these kill other insect species as collateral damage. Modern formulations of insect repellants such as DEET target mosquito odor and taste receptors, rendering the insect unable to recognize chemical signals that signal human prey.

“We have found that catnip and its active ingredient nepetalactone activate the irritant TRPA1 receptor, an ancient pain receptor found in animals as diverse as tapeworms, fruit flies and humans,” Marco said. Gallio, associate professor of neurobiology at Weinberg College of Arts and Sciences. “We now believe that catnip is so aversive to so many insect species because it activates this widespread irritant receptor.”

In previous work, the Gallio Lab and others have demonstrated that humans, insects, and many other animal species possess a potential ion channel version of the transient ankyrin 1 receptor (TRPA1), a protein better known as “Wasabi receptor” which detects environmental irritants such as pain and itching.

“What is particularly interesting is that, unlike compounds in wasabi or garlic which also activate these receptors in humans, catnip appears to selectively activate the receptor in insects,” said Gallio. “This explains why humans are indifferent to it, and provides a serious advantage for its use as a repellant.”

Why cats are so drawn to catnip is an entirely different story, and not fully understood. Research indicates that this may be due to an unusual interaction between one of the active ingredients in catnip and a molecular component present in the cat’s brain reward system.

“Mosquitoes, especially those that act as disease vectors, are becoming a bigger problem as climate change creates attractive conditions for them further north and south of the equator,” Stensmyr said. “Compounds of plant origin represent an emerging new approach to developing insect repellents, because plants have long known how to protect themselves from insect pests.”

Gallio added that repellents of plant origin are often available at a much lower cost and are easier to obtain. The accessibility of catnip could have major implications in developing countries where mosquito-borne diseases are a huge problem.

Northwestern’s Gallio lab is studying the sensory systems of Drosophila fruit fly in the lab, including the mechanisms that control external temperature and pain responses. Lund’s Stensmyr Laboratory focuses primarily on mosquitoes and other insects that are vectors of human disease.

Researchers studied various insect species to gain a better understanding of how catnip and its active ingredient work to repel a wide range of insects, while having no irritating effects on humans.

To confirm their results, the team performed a series of tests, including offering mosquitoes a blood meal in a dish covered with a nylon sock sprayed with catnip, experiments involving a wind tunnel, as well as experiments. in which volunteers place their hand in a cage. with live mosquitoes, with or without the protection of a catnip oil rub.

Gallio believes that the mechanism they discovered also provides a proof of concept for the development of next-generation repellents that exploit the same logic – selectively targeting the irritant receptor in mosquitoes.

“It’s an entry point to study how this molecule works on the receptor,” he said. “Once we understand its chemistry and how it interacts with the receptor, we could design even more potent and selectively targeted molecules.”

The team’s next project? Find out how to get rid of cats that keep chasing them.