英語時差：貓薄荷是什么？（下）

Lactones carry chemical messages inside a body, and nepetalactone carries its message straight to the pleasure center of a cat’s brain, where it can randomly excite the cat’s neural circuits associated with sex, playing, hunting, and feeding. Although a cat may try to eat catnip or a catnip toy, it is only the smell of catnip that transfers the drug to a cat’s brain, not the actual ingestion. This is why a small amount of catnip inside a toy can make a cat happy again and again. It’s also why a cat will sometimes be more interested in the cardboard box that a catnip toy came in than the actual toy–the cardboard might carry more of the smell. If your cat seems unaffected by catnip, don’t worry. A cat’s sensitivity to catnip is genetically determined, and some don’t respond at all.