New research shows how catnip and silver vine trigger euphoric feelings in cats and help keep mosquitoes away.
Catnip is known to hold a special place in the hearts of felines, which often respond by rubbing their face and head into the plant, rolling on the ground, and then zoning into a state of intoxicated rest.
But the biological mechanisms by which it works its magic, and whether it confers additional benefits on cats, had remained unanswered questions until now.
An international team of researchers published a study in the journal Science Advances on Wednesday, concluding 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 compound in silver vine responsible for inducing a euphoric state and found that it activates the brain’s opioid reward system. The substance is similar to nepetalactone, the main psychoactive compound in catnip.
Masao Miyazaki, professor at Iwate University of Japan, and lead author of the article, told AFP news agency that the team had applied for a patent to develop an insect repellant based on their findings.
The team began by testing how 25 lab cats, 30 feral cats and several big cats, including an Amur leopard, two jaguars and two Eurasian lynxes, reacted to the neetalactol-soaked filter paper.
The felines all spent more time with neetalactol infused paper than with regular filter paper that was used as a control.
In contrast, laboratory dogs and mice showed no interest in the paper containing nepetalactol.
Next, they tested the response of 12 cats to all known bioactive compounds in silver vine, confirming that nepetalactol was the most potent of the substances.
To test whether feline responses to the substance were governed by the brain’s opioid system, they took blood samples to check beta-endorphin levels five minutes before and after being exposed to nepetalactol.
Elevated endorphins only occurred after exposure to nepetalactol and not to the control substance.
When researchers gave cats naloxone, a drug that inhibits the effects of opioids, the cats no longer wanted to rub nepetalactol. Naloxone is commonly used in humans to treat opioid overdose.
But unlike opioids, scientists believe the response to nepetalactol is “non-addictive” because it works by triggering an increase in endorphins already produced by the body.
Drugs like morphine, on the other hand, stimulate opioid receptors in the brain directly, not indirectly.
Finally, they tested whether the leaves of the silver vine repelled Aedes albopictus mosquitoes when the cats rubbed against the plant.
They found that far fewer mosquitoes landed on cats that engaged in this behavior.
This, they wrote, was an example of “how animals use plant metabolites to protect themselves from harmful insects”, as seen for example in some species of birds that rub citrus against themselves or in chimpanzees who make sleeping platforms from trees with repellent qualities.