Okay, so I'm going to sound like the stereotypical intro to psych student, spouting off ideas that I'm not really sure I even remember correctly....but here goes.
Assuming I do recall correctly, my psych professor told us of an experiment kind of dealing with this subject. Since the hypothalamus in the brain is known as the "pleasure center," they implanted a little electrode type thing in a rat's hypothalamus. As I'm sure we've all heard of teaching rats to press levers in the little Skinner boxes, it was slightly similar in that everytime the rat pressed the lever, it got a stimulation of the hypothalamus...needless to say, they were very happy rats. Some of the rats would forego eating and sleeping, and they never tired of that activity. Kinda seems like you could spark some controversy over whether or not we'd like to introduce another potential addiction.
Anyhow, the guy that observed the rats, Delgado, used the same type of thing when he staged the first remote-controlled bull fight. He stepped in the bull ring and as the bull was preparing to charge, he stimulated the hypothalamus, thus transforming the bull from a raging, snorting thing ready to gore him, the bull kinda broke into a cartoon-like happy go lucky trot.
They also tried this to control rage responses in a person. Whenever the person became enraged, he had to first exhibit self-control, and he was then given a similar stimulation of the hypothalamus.