Since there are little more than "unconfirmed" reports of the benefit of MM in PD , i suggest that we all try it and come up with a verdict of just how helpful MM is in PD. I have tried it, and had considerable success with calming dyskinesia, and found that it can be the only thing that works for depression, much better than SSRI's and the like. But that is me, i am sure that it's not for everyone of us (getting "stoned" is not for everyone!) There are also anecdotal reports that the antidyskinetic and antiseizure principle is cannabidiol, which is apparently not psychoactive, and may be useful by itself. If used properly i think it has a useful role to play in PD therapy. But it still doesn't do anything to make one feel "asymptomatic", so, is probably just another palliative agent. But if it works dont try to fix it!
I tried to find anything on the web about cannabinoids being excitatory amino acid antagonists, but no real hits.