Brain and Nasal Cavity Anatomy of the Cynomolgus Monkey: Species Differences from the Viewpoint of Direct Delivery from the Nose to the Brain

Abstract

Based on structural data on the nasal cavity and brain of the cynomolgus monkey, species differences in the olfactory bulb and cribriform plate were discussed from the viewpoint of direct delivery from the nose to the brain. Structural 3D data on the cynomolgus monkey skull were obtained using X-ray computed tomography. The dimensions of the nasal cavity of the cynomolgus monkey were 5 mm width × 20 mm height × 60 mm depth. The nasal cavity was very narrow and the olfactory region was far from the nostrils, similar to rats and humans. The weight and size of the monkey brain were 70 g and 55 mm width × 40 mm height × 70 mm depth. The olfactory bulb of monkeys is plate-like, while that of humans and rats is bulbar, suggesting that the olfactory area connected with the brain of monkeys is narrow. Although the structure of the monkey nasal cavity is similar to that of humans, the size and shape of the olfactory bulb are different, which is likely to result in low estimation of direct delivery from the nose to the brain in monkeys.

In Vitro Evaluation of Nasal Aerosol Depositions: An Insight for Direct Nose to Brain Drug Delivery

“…As it is unlikely that nasal product developers will be able to carry out encyclopaedic testing in human volunteers and patients, in vivo models such as mice, rats, and monkeys have been generally used as surrogates for humans in order to evaluate the distribution of airborne materials within the nasal cavity and to provide a proof of concept for olfactory targeting and efficient brain delivery via pharmacokinetic and pharmacodynamic studies [ 16 , 17 , 19 , 20 , 36 ]. However, translating the results from these models to humans is largely debatable, not only because of the anatomical and physiological variations but also because different species have discrete inhalation patterns [ 37 , 38 , 39 ].…”

Optic chiasmatic potential by endoscopically implanted skull base microinvasive biosensor: a brain-machine interface approach for anterior visual pathway assessment

“…We employed goats to test the feasibility and safety of trans-sphenoidal implantation of the skull base electrode, as the sphenoidal anatomy and size of the goat and sheep are similar to that of humans 11 , 12 , even more so than monkeys 15 (Figure 1 F). Since airy SS does not exist in goats (Figure 1 F), we created an artificial airy SS using clinical settings of trans-nasal endoscopy, the size of which (approximately 14 mm in width) was comparable to that of human SS (approximately 20 mm) (Figure 1 F).…”