They roll around in the leaves and get into a state of intoxication: What is this strange enthusiasm of cats for certain plants about? In addition to the well-known active ingredient of catnip, researchers have now also identified the “intoxicating” substance of the even more powerful silver wine. In addition to stimulating sensations of pleasure, the iridoid active ingredients also have a practical effect, according to the studies: The substances drive away mosquitoes. The results thus suggest that cats have developed an affection for certain plants in order to protect themselves from potentially disease-transmitting pests.
In dried form, they are used as fillings in pillows and toys: Many cat owners are familiar with the amazing effects of certain herbs. The smell magically attracts the house tigers and they begin to wallow with relish in the material and to play with the filled objects. Other members of the cat family also show such reactions to certain plants. With us especially the catnip (Nepeta cataria) known as a feline “intoxicant”, but also the Asian silver wine (Actinidia polygama) is increasingly finding its way into western pet shops. This plant, also known as Matatabi, is said to have a particularly intense effect and it has a long tradition of dealing with cats, especially in Japan.
On the trail of “cat drugs”
As for catnip, the trigger for animal enthusiasm is already known: the plant substance nepetalactone from the group of iridoids causes the behavior. However, the mechanisms of action and the biological significance have so far remained largely unclear. The researchers led by Masao Miyazaki from Iwate University in Morioka have therefore now investigated the phenomenon further. The focus was on the previously barely researched silver wine. To do this, they first isolated the active ingredients in question from the plant and tested them on cats. They were able to show that the iridoid nepetalactol triggers the characteristic behavior in silver wine: house cats and large cats such as jaguars, amur leopards and lynxes react to laboratory paper filter paper mixed with nepetalactol with the same behavior that they also show with complete plant material, the scientists report.
Then they addressed the question of what exactly could be behind the euphoric effect of the substance. They investigated the suspicion that it stimulates the opioid system in cats, similar to what is known from comparable effects in humans. “We tested the endorphin levels before and after the nepetalactol-induced reaction in the blood of the test animals. In this way, we were able to confirm that the nervous system is activated, which is responsible for the euphoric response, ”says Miyazaki.
Enjoyable protection against mosquitoes
But does this mean that cats only love plants because they get “high” from them? Is the effect of the iridoids in catnip and silver wine a coincidence – or is there an overriding cause? “On the basis of indications that the nepetalactone in catnip has insect-repellent effects, we speculated that cats might protect themselves from parasites with nepetalactol or nepetalactone,” says first author Reiko Uenoyama. In this context, the researchers initially demonstrated that mosquitoes avoid the plant material of silver wine and are also deterred by nepetalactol alone. The substance therefore acts as a so-called repellent. In this context, the observations of cats made it clear that the animals rubbed their heads deliberately on paper mixed with the substance, thereby transferring them to their fur.
“Next we tested the mosquito repellent properties of nepetalactol on the cats. We counted the number of mosquitoes that landed on cats’ heads with and without the use of nepetalactol, ”reports Miyazaki. The researchers were able to confirm that the substance actually keeps the pests away from the animals. “From these results we conclude that the cats’ reaction to the iridoid substances is linked to a chemical defense against mosquitoes, and perhaps also against other parasitic insects,” says Miyazaki.
In addition to clarifying the background to the strange behavior of cats, the results could also be used to develop new mosquito repellent products, say the scientists. As you emphasize, there are still questions that you want to investigate. “Why is this reaction limited to cats? In order to find answers, we now want to identify the gene that is responsible for the reaction, ”says Miyazaki.
Source: Iwate University, professional article: Science Advances, doi: 10.1126 / sciadv.abd9135