New research shows how catnip and silver vine induce euphoric feelings in cats and help them ward off mosquitoes.
Catnip is known to hold a special place in the hearts of felines, who often respond by rubbing their face and head into the plant, rolling it on the ground, and then zoning into a state of intoxicated tranquility.
But the biological mechanisms by which it works its magic and whether it provides additional benefits for cats have been unanswered questions until now.
An international team of researchers published a study Wednesday in the journal Science Advances, in which they found that catnip and silver vine, an even more potent herb found in the mountains of Japan and China, can repel mosquitoes.
They also identified nepetalactol as the main silver vine compound responsible for inducing a euphoric state and found that it activates the brain’s opioid reward system. The substance is comparable to nepetalactone, the main psychoactive substance in catnip.
Masao Miyazaki, a professor at Japan’s Iwate University who was the senior author of the article, told AFP news agency that the team had filed for a patent to develop an insect repellent based on their findings.
The team began by testing how 25 lab cats, 30 feral cats and several large cats, including an Amur leopard, two jaguars and two Eurasian lynxes, responded to filter paper soaked in nepetalactol.
The felines all spent more time with nepetalactol-infused paper than with the regular filter paper used as a control.
In contrast, dogs and laboratory mice showed no interest in the nepetalactol-containing paper.
They then tested how 12 cats reacted to all known bioactive compounds of silver vine, confirming that nepetalactol was the most potent of the compounds.
To test whether the cat’s responses to the substance were controlled by the brain’s opioid system, they took blood samples to check beta-endorphin levels five minutes before and after they were exposed to nepetalactol.
Increased endorphins only occurred after exposure to nepetalactol and not after the control substance.
When the researchers gave the cats naloxone, a drug that inhibits the effects of opioids, the cats no longer wanted to rub against the nepetalactol. Naloxone is often used in humans to treat opioid overdose.
But unlike opioids, the scientists think the response to nepetalactol is “non-addictive” because it works by causing an increase in endorphins already produced by the body.
In contrast, drugs such as morphine directly, not indirectly, stimulate the brain’s opioid receptors.
Finally, they tested whether silver vine leaves repelled Aedes albopictus mosquitoes when cats rubbed the plant.
They found that significantly fewer mosquitoes landed on cats that engaged in this behavior.
This, they wrote, was an example of “how animals use plant metabolites to protect against insect pests,” seen, for example, in some bird species rubbing citrus fruit against themselves or chimpanzees making sleeping platforms from trees with repellent properties.