β-Amyloid peptide (1–40) in the brain reaches the nasal cavity via a non-blood pathway

• High level of 125I-Aβ40 was detected in the nose of rats receiving an icv injection.
• Nasal 125I-Aβ40 level was low in rats that received an intravenous injection.
• Aβ injected into the cerebral ventricle spreads to the nose via a non-blood pathway.

We examined the distribution patterns of human β-amyloid (1–40) peptide labeled with iodine 125 (125I-Aβ40) after injections into the cerebral ventricle or tail vein of rats. In rats receiving an intravenous injection, the radioactive concentration of 125I-Aβ40 in the nasal area was similar to other extracranial organs. In contrast, the caudal part of the nasal area in rats receiving an intracerebroventricular injection displayed a high level of 125I-Aβ40 radioactivity. These results suggest that Aβ reaches the nasal cavity from the brain via a non-blood pathway.