My 2 cats LOVE catnip. They start to roll over, look with crossed eyes, drool, and are totally out of space. They also like to lick the little catnip bag till it's soaking wet.
But, as soon as the dog has been playing with it, they pretend to have lost all interest in catnip, until I come home with a new little bag for them.
My old cat that passed away, used to sleep with her head on a little catnip pillow.