Why does a cat.....

Why do some cats go crazy over catnip, but others ignore it?
The response to catnip is the result of a gene in the cat; if the cat doesn't have the gene, it cannot physically react to catnip. Some cats will react to catnip by rolling around on the floor in delight, others will just quickly eat it up and wander off, while others will ignore it completely. It's like a cat cocain.

Catnip (Nepeta cataria) is a plant in the mint family that grows wild as a weed and is found throughout the United States, particularly in the Midwest.

Cats under three months of age usually do not respond to catnip. Most older cats typically become excited or aroused as they smell, chew and eat catnip. They will frequently salivate, roll and rub, and sometimes run and leap in the air when responding to the catnip. It may be applied to scratching posts or used in stuffed toys.

Not all cats are stimulated by catnip to the same degree, and over a third of cats will not respond at all. Strange as it may seem, the different responses are probably due to environmental factors, genetics, and the gender of the cat (males are more likely to respond than females). If a cat who normally reacts to catnip is in a strange environment or is anxious, she may not react to the catnip. Cats in certain genetic 'lines' do not react to catnip. No one really understands the genetic trait, but it can be bred into a line through genetic selection.

The cat-active ingredient in catnip is 'nepatalactone.' This substance closely resembles a chemical found in the urine of female cats. This may be why unneutered males generally have more of a reaction to catnip than females and neutered males.