It is not clear how catnip affects cats but it's invariably a revelation to see a cat react to catnip, a plant that smells strongly of mint. The cat goes into throes of ecstasy & excitement, behaving as if it were on drugs. It begins to salivate and sniff and chew in a possessed manner.
Many cats begin to grind their bodies against the floor or the wall. Some even become giddy and loose balance as they try to walk roughly the room. Cats also show a assured degree of forceful behavior as they kick out with their front paws and flex their claws
Although it is not officially known as to why cats behave in the way they do after taking catnip, but some of their reactions are quite predictable. They loose their aggressive attitude, their inhibitions seem to melt away and they seem to embark on a fun trip very much like human beings under the influence of marijuana.
It is also possible that catnip has a sexual effect on cats because they are seen rolling and rubbing against hard objects (this works for male as well as female cats). Incidentally, kicking out is a symbol of predators, not of cats.
Science too has not been able to explain satisfactorily the effect of catnip on cats. However, it has been able to identify the substance in the catnip that affects cats. It is a volatile chemical called 'nepetalactone'. This chemical does not affect all cats, but only those cats that actually chew on the plant.
Nepetalactone has an opium-like molecule and an opium-like action in that, it stimulates certain pheromones in cats, which in turn sensitize certain receptors, quite similar to the effect morphine has on humans. It has a certain excitatory effect on the hypothalamus, the place of the brain that controls appetitive, predatory and sexual behavior in cats.
Catnip is not necessarily harmful for cats. In fact, it has some useful, medicinal properties that are rapidly being developed. However, for cat owners catnip remains a mysterious plant with its small, plane flowers. They can only gasp in amazement when they see their cats react to this plant. Some even give catnip to their cats for fun. However, this is an activity that should be avoided. There is always the possibility that the cat may get hooked on the plant, and behave in an abnormal manner.