Figure 8.

Schematic of the mechanisms associated with the transport of peptide drugs to the brain after intranasal coadministration with CPPs. The peptides travel directly from the nasal cavity to the olfactory bulb or CSF and further diffuse through the olfactory bulb or CSF or are distributed via perivascular spaces deeper into the brain. The fractions of the peptide drugs absorbed systemically or transported to the trigeminal nerves cannot contribute to the distribution to the brain. Insulin delivered to the brain by coadministration with CPPs can accumulate in the hippocampus.