An international team of researchers has discovered that catnip and silver vine offer cats more than just feelings of intoxication and euphoria. The chemicals in these attractant plants also provide cats with protection from mosquitoes, according to a study led by Iwate University.
“The first appearance of silver vine (“Matatabi” in Japanese) as a cat attractant in literature in Japan dates back to more than 300 years ago,” said Professor Masao Miyazaki. “A folklore Ukiyo-e drawn in 1859 shows a group of mice trying to tempt some cats with a smell of silver vine. Still, benefits of the cats’ response had remained unknown.”
Cats experience undeniable feelings of pleasure when they encounter catnip or silver vine. They rub their faces against the plants and sniff them, roll around on the ground, and ultimately lounge around in a seemingly intoxicated state.
Despite the strong effects, the specific component of cat attractant plants underlying the response has been a mystery, as well as the neurophysiological mechanisms involved.
The researchers isolated the substances in silver vine leaf extracts and administered each of them to cats. They found that the most potent active ingredient is nepetalactol, which activates the opioid reward system in both domesticated and big jungle cats.
“We applied nepetalactol to laboratory paper filters and tested with eighteen laboratory and seventeen feral cats. They displayed the typical response to silver vine. We also tested the substance with larger, non-domestic cats (jaguar, Amur leopard, and Eurasian lynx). They showed a similar reaction. We concluded nepetalactol is responsible for the typical feline reaction to silver vine,” explained study first author Reiko Uenoyama.
The experts theorized that the cats’ opioid reward system, which is associated with euphoric effects in humans, is activated by the intoxicating plant compound.
“We tested β-endorphin levels before and after nepetalactol-induced response in cat blood. We found that silver vine activates the nervous system that is responsible for the euphorigenic reaction,” said Professor Miyazaki.
Since this reaction was already shown in feline animals when they evolved from other species about 10 million years ago, the researchers believed that the plant had another biologically important function.
“On the basis of some reports that nepetalactone, the feline attractant in catnip, has mosquito repellent activity, we thought that the response allows cats to transfer plant’s nepetalactol or nepetalactone on their fur for protection against mosquitoes. This led to a strong hypothesis when we found the mosquito repellent activity of nepetalactol.” said Uenoyama.
To investigate whether cats purposefully transfer nepetalactol, the team placed paper filters with nepetalactol on different parts of the cat cage, including the floor and ceiling. The results of the experiment showed that the cats make it a priority to transfer the substance to their faces and heads.
“Next, we tested the mosquito repellent property of nepetalactol on cats,” said Miyazaki. “We counted the numbers of mosquitoes landing on cat heads with and without application of nepetalactol. The mosquitoes landed less on the nepetalactol heads.”
“To see whether mosquitoes react the same in a more natural setting, we compared the mosquito reaction between cats that responded to silver vine leaves and nonresponsive cats. Mosquitoes avoided the responsive cats.”
“From these results, we found that the cats’ reaction to silver vine is chemical defense against mosquitoes, and perhaps against viruses and parasitic insects. This was the most significant finding of our study.”
Based on the results, the researchers see great potential for many future studies and practical applications.
“Why is this reaction limited to cats? Why don’t non-feline animals react to the plant? To find answers, we want to identify the gene responsible for the reaction. The findings of this study may be used in various applications, including development of new mosquito repellant products.”
The research is published in the journal Science Advances.
By Chrissy Sexton, Earth.com Staff Writer