[xlib]

No clue. Not my area of expertise—I have no idea what a “perivascular membrane of Held” is, much less how to get past one.

[Rudder]

Functional name is the blood-brain barrier that serves to keep the brain protected from certain materials in the blood from getting into (or out of) the brain. Many agents do not pass this barrier and thus, many drugs have to be in the form of precursors (raw materials rather than the assembled drug) to be assembled in the brain.

Thanks for your reply.