system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What exactly is happening to our cats when we give them catnip?

What's with the dialated pupils and erratic behavior that some cats display after being given catnip? 

Is it like an actual drug for cats? Should there be a limit that we as humans should be aware of as to not injure our pets? Is it addictive?
gpt
Yep, they are getting high.
Nepetalactone is a volatile compound in catnip. The smell induces olfactory neurons which project to the brain and causes a response. 

The amygdala of the brain integrates the the signal from the olfactory neurons and projects to areas like the hypothalamus. The hypothalamus regulates hormonal responses through the pituitary gland. This creates a "sexual response." The cat essentially reacts to an artificial cat pheromone. 

Human brains do react to catnip but not in the same manner, the plant tends to cause relaxation.