Feline Aggression

[SierraRose]

I adopted an 8-9 week old kitten (a Khao Manee mix/Siamese) about two months ago, and when I first brought him home he was kind and gentle. I gradually introduced him to my very laid back senior cat, and she swatted him once. Ever since that day, my kitten has displayed extreme and ruthless aggression towards me and my senior cat. I've never ever been able to pet him because he bites and scratches extremely hard, and always plays very rough, picking him up is out of the question. I think I've tried all the methods to train a cat not to attack humans, unfortunately, nothing seems to work! I only use his toys to play with him (he has lots of them- including scratching posts, condos, balls, and mice) and not my hands (thought he prefers to attack my hands and face), that water gun/bottle trick? He LOVES water and will just sit there and try to drink the water I squirt at him, picking him up by the nape of his neck drives him crazy and has no effect on him - instead of calming down, he becomes wild and manages to claw my hands. I'm hoping once I have him neutered he will calm down slightly. But recently, I've found he has been hurting my senior cat, and I just cannot allow that to much longer. Does anyone have any ideas or suggestions, experiences perhaps? I feel like I have a possessed cat! Are there personality disorders for felines? Are there medications out there? My vet reccommended anti-depressents as even he belives he's out of control, has anyone had experiences with medications? Any help greaaatly appreciated!!:)