Jeanb,
You are right, the dosage is all important. In

http://www.aboutxinjiang.com/Science...nt_1977627.htm
it says,
"The research team by James Surmeier implanted a time-release capsule of the drug beneath the skin of mice that had just reached adulthood. This implant released a daily dose of isradipine that, if scaled up for humans, would correspond to roughly 10 times the dose for a person with hypertension, but less than the amount given to treat stroke."

It looks as if you need a much higher dose to see an effect on your PD.

Actually, the British PDS (Parkinson's Disease Society) have asked me to write an article for their magazine, after I alerted them to the link with hypertension drugs.
The other hypertension drugs are:
Ramipril
Burinex
Hydrazoline
Captoprill,
Tetrazosin.
I am investigating the effect of these drugs on the BBB, and am corresponding with a professor who specialises in the role of the BBB in MS.
I have personally met two people who were diagnosed with PD up to 20 years ago, and have never needed any PD medication. One has taken Ramipril for many years for hypertension, and the other has taken Burinex for years.
Ron