New research shows how catnip and silvery vines cause feelings of euphoria in cats and help them ward off mosquitoes.
Catnip is known to occupy a special place in the heart of cats, which often respond by rubbing their faces and heads on the plant, rolling on the ground and then zoning into a drunken state of rest.
But the biological mechanisms by which it works its magic and gives some additional benefit to cats, have remained unanswered questions until now.
An international team of researchers published a study in the journal Science Advances on Wednesday, finding that catnip and silver vine, an even more potent herb found in the mountains of Japan and China, can ward off mosquitoes.
They also identified nepetalactol as the main compound in the silver vine responsible for inducing a state of euphoria 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, a professor at Iwate University in Japan, who was the senior author of the article, told AFP news agency that the team had applied for a patent to develop an insect repellent based on their findings.
The team began by testing how 25 laboratory cats, 30 wild cats and several large cats, including an Amur leopard, two ounces and two Eurasian lynxes responded to the filter paper soaked in nepetalactol.
All cats spent more time on nepetalactol-infused paper than on regular filter paper used as a control.
In contrast, dogs and lab rats showed no interest in the paper containing nepetalactol.
They then tested how 12 cats responded to all known bioactive compounds in the 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.
High concentrations of endorphin occurred only after exposure to nepetalactol and not to the control substance.
When researchers gave cats naloxone, a drug that inhibits the effects of opioids, cats no longer wanted to rub against nepetalactol. Naloxone is commonly used in humans to treat an opioid overdose.
But, unlike opioids, scientists think the response to nepetalactol is “non-addictive”, as it works by triggering an increase in the endorphins that are already produced by the body.
Drugs like morphine, on the other hand, stimulate the brain’s opioid receptors directly, not indirectly.
Finally, they tested whether the silver vine leaves repelled Aedes albopictus mosquitoes when cats rubbed against 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”, which is seen, for example, in some species of birds that rub citrus on themselves or on chimpanzees that make platforms for sleeping on trees with repellent qualities.