A thought as to; Why our Parkinson’s brain is not making Dopamine?
Dopamine is synthesized in various regions around the body unable to cross the blood brain barrier (keeping it isolated from the Central Nervous system) and there is no doubt a ‘trigger or keys’, that act upon it; Braking and regulating supply and demand, to inhibit and dispose of any overloads in production.
It would only take a little wee virus, to hook up upon those ‘triggering keys’, before carrying them across the blood brain barrier, into the Central Nervous system; especially when the ‘good Microbiology’ in the gut and airways are not wholly up to scratch. And the destruction of the Dopamine system in the brain begins (even after the mechanisms within the brain have effectively eradicated the virus).
Headache & Flu symptoms?