It has been done before!! They even used dopamine.
It got to the brain via the nasal passage,
"These molecules appeared rapidly in the CSF, although hard evidence of direct transfer
from the nose remains elusive."

So they had problems using scientific tests to get hard evidence of how much reached the target.
But PDers can test easily by measuring effect on our symptoms. The effect would be extremely rapid, with no dyskinesia or side effects, since none goes into the blood.

However, they recognise the value of the nasal route.
"The nasal administration of drugs offers advantages over administration by intravenous
injection. Drugs can be rapidly absorbed through the nasal mucosa, resulting in a rapid onset
of action, and also avoiding degradation in the gastrointestinal tract and first-pass metabolism
in the liver. Targeting the brain via nasal administration offers potential for the development
of new drugs."
See
http://www.diva-portal.org/diva/getD...__fulltext.pdf

Ron