Read with caution!
This post was written during early stages of trying to understand a complex scientific problem, and we didn't get everything right. The original author no longer endorses the content of this post. It is being left online for historical reasons, but read at your own risk.
Apparently the nasal-CNS connection can sometimes allow drugs administered as nasal drops or sprays to bypass the blood-brain barrier and access the brain directly. In this case a Japanese team was able to get methotrexate (a non-BBB crossing antitumor agent) to the brains of rats by taking advantage of what they term “nose-brain direct transport.”