As far as cannabiloid antagonists, I don't know. I do know that there are two different chemicals in weed that affect you. There's THC which gets you high, and there is CBD, which calms you down. The relative levels of these chemicals determines the type of high you have. THC makes your brain think crazy things (i.e. be high) but can lead to anxiety. CBD fights anxiety but can also lead to couch lock. CBD has been studied for use as an anti depressant and for use in treating people with schizophrenia.
I still smoke weed all the time, but it was only after 9 months of not smoking or drinking anything. Weed makes visuals/DP slightly worse, but its not phasing amount, and I cope with it so easily it almost doesn't even matter. If I smoke a lot, however, it does get substantially worse, dying down in a day or two, usually within the day.
Yesterday is a good example: people are getting off school, and yesterday I smoked probably 5 or 6 js with others during the evening. Today I feel like total shit, DP really bad. But that said, I know what it is, so I'm no freaking out that badly at all. In fact, if I had felt this way a year ago, I would be having a full on panic attack. Not anymore. You just gotta be careful and keep the necessary perspective. I regret what I did yesterday (seemed fun at the time), but at least I know how to cope with it today.