Effects of osthole microemulsion by nasal administration on the cholinergic pathway in mice treated with scopolamine
Authors: Hou Xueqin , Xu Li , Liu Xiaoqian , Zhang Han-Ting 
Published: April 2020

Objectives

Osthole is the main active component of Fructus Cnidii, which is the dry ripe fruit of Cnidium monnieri (L.) Cuss. and has long been used in clinic practice with pharmacological activity in the central nervous system (CNS). However, Osthole exhibits low bioavailability, fast distribution and elimination, and low concentrations in the brain when given orally. In this study, we aimed to develop a new dosage form to increase the concentrations of osthole in the brain and enhance its pharmacological effects in the CNS through reducing the dosage and improving the stability and bioavailability. Thus, osthole microemulsion was prepared to investigate its effects in Alzheimer’s disease model mice.

Methods

Osthole microemulsion was prepared, and the particle size and distribution were detected. The effects of osthole microemulsion by nasal administration on learning and memory abilities in scopolamine‐treated mice were assessed by behavioural tests. The superoxide dismutase (SOD) activity, glutathione (GSH) level and malondialdehyde (MDA) content in the serum were examined. Choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) expressions in the olfactory‐basal forebrain were detected. The acetylcholine (ACh) level and the histological morphology in the brain were also measured.

Results

The average particle size of 1μg/μl osthole microemulsion was less than 15 nm. It was characterized as sphere under the transmission electron microscopy, and the osthole was completely encapsulated in the microemulsion core. Morris water maze and novel object recognition tests showed that osthole microemulsion improved spatial and object learning and memory in scopolamine‐treated mice. Moreover, osthole microemulsion restored the abnormal activity of SOD and increased the levels of MDA and GSH in the serum. Brain immunohistochemistry staining showed that osthole microemulsion up‐regulated ChAT expression, while down‐regulated AChE in the olfactory‐basal forebrain cholinergic pathway. Additionally, the ACh level and pathological morphology in the brain were also reversed after nasal administration with osthole microemulsion.

Conclusion

The concentration of 1μg/μl of osthole microemulsion is an ideal dosage form with small particle size, uniform distribution, and high permeation. Osthole microemulsion ameliorates memory impairment induced by scopolamine in mice, likely via the olfactory‐basal forebrain cholinergic pathway and by ameliorating oxidative stress. This may have an implication for the development of intranasal brain targeting drugs via the nose‐brain pathway as potential treatments of certain CNS disorders.

Support or Funding Information

The present study was supported by research grants from the National Natural Science Foundation of China (grant no. 81773717 and 81703901), the Shandong Province Natural Science Foundation of China (grant no. ZR2016HB56), the Foundation of Overseas Distinguished Taishan Scholars of Shandong Province, and he Taian Municipal Science and Technology Bureau funding (grant no: 2016NS1078).