Hello Johnt,
We can manipulate the permeability of the BBB to some extent
using the substances mentioned above. Those drugs that widen the permeability (stress and growing old also,), cause a worsening of symptoms. Those materials that reduce the permeability will improve symptoms.
However, the change in permeability will only be temporary while the drugs are present.
In the case where the permeability is above the threshold, dopamine can leak in both directions until equilibrium is established.
The dopamine would only go through the BBB where the person has PD and their BBB permeability is above the threshold value.
Since Prof Al Lossinsky has confirmed that it is possible to measure the permeability without waiting for the patient to die!! there are several intriguing experiments you could do.
In a group of PWP's with a spectrum of years since diagnosis, say from 2 years to over 20 years, and measure their permeability. They must all be in a steady state, no food or meds for say 3 hours. Then plot a graph of years since diagnosis against permeability, and see whether you get essentially a straight line graph. Take alpha lipoic acid, curcumin etc and measure the effect on permeability.This would give a league table showing the best (and worst ) supplements. Determine the level of permeability at the threshold value, etc.
Plenty of Ph.D topics!!
Ron