The attached link is a Doctor dissertation which examines Parkinson's disease therapies till 1980. It is a comprehensive 876 page document which goes into great detail. So if you want to hear the inside story of anticholinergics, amantadine, levodopa, mucuna pruriens, Benadryl, etc, etc, etc....this is for you. If you are only interested in specific topics do not despair. If you open the document with Acrobat 9 there is a search engine under the 'Edit' tab in the upper left corner. Open the tab and scroll down to 'Search'. Type in your word and hit enter. I am on page 300 and find it fascinating. To give you an idea as to its content the author examines all the past therapies and, believe it or not, at one point circa 1920 doctors thought inducing a fever was good for PD patients. What did they do? They gave PD patients malaria....you read that right.
I hope you find this interesting.