Just a nip


Catnip and other members of the mint family produce whole bouquets of chemicals, mainly to ward off infections and enemies, generally without interesting cats.

Just a nip
• 01 October 2005
• From New Scientist Print Edition. Subscribe and get 4 free issues.
Why do cats love the plant catnip? What is the evolutionary benefit of this affection to either the plant or the cat?
The main active ingredient of catnip is nepetalactone. Its structure has little obvious resemblance to mammalian biochemicals, but just happens to fit particular receptor molecules. In several carnivores, nepetalactone molecules seem to fit vomeronasal receptors for sex pheromones and induce orgasmic behaviour, complete with a period of resolution.
The response is genetically determined; some cats are unaffected. This supports the suspicion that nepetalactone is different from the real pheromone. The drug should be of little selective relevance to cats, because few of their ancestors would have encountered catnip lactones.
It is not easy to see what selective advantage the plant could gain from stimulating carnivores with what amounts to a recreational drug. In fact, the whole thing might be coincidental and irrelevant to the plant. Catnip and other members of the mint family produce whole bouquets of chemicals, mainly to ward off infections and enemies, generally without interesting cats.
Nepetalactone is important to humans as an insect repellent, insecticide and microbial inhibitor.
Jon Richfield, Somerset West, South Africa
Cats love catnip (nepeta cataria) because it stimulates their olfactory love receptors.
The herb, a member of the mint family, releases nepetalactone when crushed. Nepetalactone closely resembles a chemical found in the urine of female cats. It binds to cat olfactory receptors that are involved in sexual stimulation, including those of large wild cats such as cougars and bobcats. In humans, herbalists have been using catnip as a sedative for centuries.
The cat's response to catnip is just an evolutionary joke or accident. But the benefit to the plant over the past few centuries has been substantial. A herb that was originally native to the Mediterranean has been spread around the world by cat lovers, and is now considered a weed throughout much of North America.
Nelson D. Sherry, Monmouth, Oregon, US
My dog, a cocker spaniel, also likes catnip. She takes the cat's catnip-filled toys and opens them up to get the filling out. I have consulted veterinarians, but they have no idea as to why this should be.
John Heckler, Bethesda, Maryland, US
From issue 2519 of New Scientist magazine, 01 October 2005, page 81

Posted: Mon - November 21, 2005 at 10:45 PM          

©