How old is he?
Older animals have been known to suffer from dimentia, so you may actually be on the right track with the "doggy Prozac" idea.
He's about 11 or 11 1/2 years old. This is the same dog that needed a toe amputated a couple of months ago. He was found under someone's (friends of my sister) hibachi cover in the rain, skinny and I suspect abused and abandoned. He's always been food aggressive, made worse by my dad feeding him from the table (you can't tell Dad what to do), which then gave everyone else the idea to do it. I'm the only one who doesn't.
Thanks for the links, Dee. The one that mentioned the various meds also mentions behavior/training, and I don't think my parents are going to change. Dad's too stuck in his ways (esp. with the memory issues that he has), and my mother is too overwhelmed with Dad and her health issues.
There is a local vet who does house calls, so that might be an option if they don't need to have him in the office. If they do need him there, though, that's a problem because he also has hip issues and he can't get in/out of a car anymore, and he's about 100 lbs so getting him in/out is very difficult. But I can suggest it to my mother and see if she wants to have the vet come out. The worst they can do is say "no."
The article also mentioned a behaviorist. I don't think the vet's office has one, but I do know of one near NYC. That brings up the issue of getting him there, though.
I will definitely pass on this information to my mother. There's no guarantee she'll act on it, but it's worth a try. Meanwhile, I think I'll pick up some doggie pheromones and bring them the next time I visit. At worst, it won't have any effect, but what's it hurt to try?
Thank you all so much, and please, if you have any other suggestions/questions, feel free to post them.