When exposed to catnip or silvery vines, cats have some very predictable behaviors, such as licking and chewing leaves, rubbing their heads and faces on plants and rolling on the ground. Cats love these plants, but surprising new research points to a more practical purpose than just wanting to get high.
Nepetalactol – the most potent active ingredient in catnip (Nepeta cataria) and silver vine (Actinidia polygama) – provides cats with a chemical defense against mosquitoes, according to the new search published in Science Advances. The discovery may explain why felines, whether domesticated cats or giant jungle predators, exhibit similar behaviors after being exposed to these plants.
The new research, led by Masao Miyazaki from Iwate University in Japan, offers new insights into nepetalactol and how it affects feline behavior and its opioid receptors. That nepetalactol stopping mosquitoes is an amazing revelation and could result in an entirely new class of insect repellent, according to the researchers. Nepetalactol had previously been linked to mosquito repellent activity, but “our data is the first to show this,” explained Miyazaki by email.
In addition, the new article is “the first to show that nepetalactol is a potent bioactive compound for cats”. In fact, it is no secret that the chemical has some kind of neurological effect in cats, but catnip, a plant in the mint family, and the silver vine, a type of kiwi, contain a multitude of other bioactive compounds, such as isoiridomyrmecin, iridomyrmecin, isodihydronepetalactone and dihydronepetalactone. Miyazaki and his colleagues, including researchers at Nagoya University in Japan and the University of Liverpool in the United Kingdom, focused on nepetalactol because of its suspected potency.
After coming in contact with catnip and silver creeper, cats have some stereotyped behaviors, such as rubbing their heads and faces on plants, rolling on the ground and giving the impression of euphoria. This lasts for about five 15 minutes and is followed by the collision phase, in which cats rest for about an hour or more. The effect that these plants have on cats has been known for centuries, but scientists don’t fully understand the purpose of all of this, as a biological or evolutionary reason for it – assuming it is not just a peculiar coincidence that has to do with the feline brain.
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To learn more, the team studied a group of different felines, including 25 lab cats, 30 wild cats and several large captive cats, including leopards, jaguars and lynx. They documented the cats’ reactions filter paper mixed with nepetalactol. ANall the cats exhibited the classic behavioral response. Dogs and exposed mice for the chemist did not display an answer.
Scientists also studied the reactions of cats to some of the other bioactive agents found in the silver vine and found nepetalactol is the most potent.
“This study found that … nepetalactol is the main bioactive compound in the leaves of the silvery vine that induces friction and rolling characteristic in cats,” write the authors in their study. “In addition, nepetalactol had similar bioactivity in Amur leopard, jaguar and Eurasian lynx. Like most [feline] species tested so far have shown positive responses to catnip (13 of 21 species tested out of a total of 41 live species in this family), this characteristic response to nepetalactol is likely to be common in many [felines]. “
The group also measured the cat’s endorphin levels before and after exposure, finding that the feline reaction to nepetalactol is regulated by its opioid system; elevated levels of endorphins were only observed after exposure to nepetalactol. Furthermore, when scientists suppressed their opioid receptors with special drugs, cats no longer exhibited their characteristic behaviors when exposed to the chemical.
As for silver vine’s role as a possible mosquito repellent, the researchers found that herenepetalactol-covered ts attracted significantly less mosquitoes, specifically the species A. albopictus, than the untreated control group –in some cases, up to half.
“These results show that nepetalactol, transferred to the face and hair on the head when rubbing on silver vine leaves, works as a repellent against A. albopictus in cats ”, write the authors. “This is compelling evidence that the characteristic scrub and roll response works to transfer plant chemicals that provide mosquito repellency to cats.”
This, argue the authors, could explain why the behavior evolved. Cats get stoned with these plants, roll around in the leaves and, inadvertently, are protected against mosquitoes in the process. This theory makes a lot of sense, but scientists now need to explain why this behavior is not seen in other animals, and whether the repellent action actually happens in nature, not just in a laboratory setting. We also need to find out if nepetalactol works to repel A. aegypti, mosquito responsible for the spread of yellow fever, dengue and zika.
Miyazaki said there may be a good reason for cats to develop this special relationship with catnip and silvery grapevine. Many cats “rely on stealth to chase and ambush their prey”, demanding that they remain quiet and still, he said. A repellent that “reduces your susceptibility to the irritation of mosquitoes that bite and the diseases transmitted by these insect vectors will likely provide a strong selective advantage”. This explains why this characteristic was maintained by many species of cats, but “it does not explain why the behavior evolved only in cats,” said Miyazaki.
One possible explanation is that an ancestor of modern cats developed special olfactory receptors, which it may have been a “crucial pre-adaptation” that provided the opportunity for this behavior to evolve, speculated Miyazaki.
Looking ahead, the team wants to identify the olfactory receptors linked to nepetalactol, as well as the genes responsible for the behavior. Miyazaki said the team members had tested nepetalactol in their arms, and seemed to keep mosquitoes away. But this “is just for patent data,” he said.
Ah yes, the almighty dollar. But this is a in which case good science can lead to a good and welcome commercial product. In fact, researchers may have found a new type of mosquito repellent, but time will tell if it really works better than conventional repellents and it makes economic and practical sense to synthesize this compound in large batches.