From the humble domestic cats to the mighty tyrants of the animal world - lions and tigers - the felines have a soft spot: they are extremely vulnerable to a volatile oil encountered in the stems and leaves of the catnip (catmint) plants (Nepeta species, from the mint family).

When cats smell catnip, they start displaying behaviors which are common to that to heat: they rub their genitals, roll over, vocalize and salivate. The response can be 10 minutes long, after which the cat turns temporarily immune to the plant's effects for about 30 minutes.

The sensitivity of the felines to catnip is genetic; about 70 - 80 % of cats display this behavior, while the rest are indifferent to the catnip's presence.

Still, the plant is non-addictive and harmless. Catnip does not affect kittens which have not reached their sexual maturity (that happens at about 6 months) yet.

Catnip plants synthesize volatile oils, sterols and tannins and grow naturally in Europe, Asia and Africa, being an exotic weed and garden herb in North America.

Nepetalactone, a terpene from the plant's volatile oils, binds to the olfactory protein receptors from the felines' noses (not to their mouth olfactory organ). The messages go through the neurons in the olfactory bulb, and from there into several brain areas, like the amygdala (involved in the emotional responses to stimuli) and the hypothalamus (which tunes the body's processes, from hunger and emotions to... sex!)

The amygdala integrates the olfactory signals to behavioral responses and the hypothalamus triggers through the pituitary gland a "sexual response." Thus, the plant's chemicals act like an artificial cat pheromone.

Human sexual physiology relies little on pheromones and smells, that's why we cannot experience sexual arousal by smelling catnip, but the plant is employed in folk medicine against the uncontrollable cries of infant colic and as a mild sedative in some herbal teas. Herbalists employ it to ease headaches and to relieve cramps, gas, indigestion, insomnia, nervousness and anorexia, arthritis and soft tissue swelling due to injury.

A plant that induces a similar response in cats is the valerian (Valerinan officinalis).