In certain neurosurgical procedures, like fixing pituitary glands, surgeons can remove a tumor through the nose with minimal damage to surrounding tissue. It turns out, that passing things in the other direction—into the brain through an intranasal route—has many advantages too. Everything from drugs, proteins, and gene vectors, to stem cells, can now by administered in this way. The major question for today, is not so much what do these agents do, but where do they go once they are inside? StemGenex, a La Jolla-based company, has recently announced their new hopes for a treatment which could potentially address several neurological diseases. They are now offering a therapy for patients with multiple sclerosis in based on the intranasal delivery of mesenchymal stem cells.
The preferred medical term for act of snorting is insufflation. While insufflation is an obvious choice to deliver drugs to the sinuses or lungs, it is now appreciated that many bioactive agents can get much further than that. One major advantage of this method is the low barrier of entry through the mucous membranes into the bloodstream. Although some pro-drugs, like codeine, require absorption through the gut to pass to the liver where they can be metabolized into an active form, many other drugs are compromised by a digestive passage. What’s more important though here for the brain, is that the normally-intact blood brain barrier can by bypassed either by slipping around the perineural sheath cells, or getting endocytosed and retrogradely transported along either the olfactory nerves, or the trigeminal nerves.