I found some articles by Dr. Jennings, etc. which explain a little bit of the ideas.

Here's an old article so it doesn't mention PD specifically though that is currently an active area of interest.

http://williamritter.com/CM_Research...0The%20Jaw.pdf

Among many other effects, too much substance P depresses nerve growth factor leading to neurodegeneration. Here is a full list of its effects.

http://web.me.com/thriiive/Summit_9/...20main03-3.pdf

Here is another older article. He is now of the opinion that in almost every case, PD is actually the result of a TMJ disorder.

http://web.me.com/thriiive/Summit_9/...ONTMJpub-1.pdf

Here is an article from Japan with an interesting experiment. Grinding the teeth down on one side of a dog's jaw yielded PD type symptoms on the opposite side.

http://parkinsonstmj.com/wp-content/...in-dogs019.pdf