answer:I cannot tell you if it changes the whole nature of the cat, but it does seem to make them more docile. I had a male kitten we intended to neuter; however, he got out of the house one night. After that he behaved the way your cat did originally, he would dart for the door whenever it looked like someone was leaving. We could not keep him in the house even though where we lived the cats were not supposed to just roam. He would disappear for days. He got to the point that I was the only one he would let touch him. Basically, he became feral. He got in multiple fights as evidenced by the wounds. The vets would not treat him because he was so aggressive. We never could get him neutered. We have had all of our subsequent cats spayed or neutered and never had a similar problem with aggression. I guess the point is twofold. Although it may change their temperament, it can make them more domesticated. Also, it keeps them from pro-creating when there are already too many cats without homes.