Have you wondered why some cats exhibit strange behavior when exposed to catnip? They act much like a female cat in heat: They may rub their head and body on the herb or jump, roll around, vocalize and salivate. This response lasts for about 10 minutes, after which the cat becomes refractory to catnip's effects for roughly 30 minutes. Response to catnip is hereditary; about 70 percent of cats exhibit this behavior in the plant's presence, although it does not affect kittens until they are about six months old and begin to reach sexual maturity.

The genetically susceptible cats are responding to a volatile oil in the stems and leaves of the plant Nepeta cataria and other Nepeta species, which are members of the mint family. When the oil, named nepetalactone, enters the cat's nasal tissue, it apparently binds to proteins that stimulate sensory neurons. These nerve cells, in turn, provoke a response in neurons in the brain's olfactory bulb, which project to several regions of the brain, including the amygdala (two neuronal clusters deep in the temporal lobes that mediate emotional responses to stimuli) and the hypothalamus (the brain's “master gland”), which is known to play a role in regulating everything from hunger to emotions.

The hypothalamus, acting through the pituitary gland, alters hormonal levels to spur the sexual-like response. In other words, the cat essentially responds to the oil as if it were a pheromone emitted by another cat. Catnip is considered to be nonaddictive and completely harmless to cats.